display(1)

NAME
display - display an image on any workstation running X

SYNOPSIS
display [ options ...] file [ [ options ...] file ...]

DESCRIPTION
Display is a machine architecture independent image processing and display program. It can display an image on any workstation screen running an X server. Display can read and write many of the more popular image formats (e.g. JPEG, TIFF, PNM, Photo CD, etc.). With display, you can perform these functions on an image:
    o load an image from a file
    o display the next image
    o display the former image
    o display a sequence of images as a slide show
    o write the image to a file
    o print the image to a Postscript printer
    o delete the image file
    o create a Visual Image Directory
    o select the image to display by its thumbnail rather than name
    o copy a region of the image
    o paste a region to the image
    o undo last image transformation
    o half the image size
    o double the image size
    o resize the image
    o restore the image to its original size
    o refresh the image
    o crop the image
    o cut the image
    o flop image in the horizontal direction
    o flip image in the vertical direction
    o rotate the image 90 degrees clockwise
    o rotate the image 90 degrees counter-clockwise
    o rotate the image
    o shear the image
    o trim the image edges
    o invert the colors of the image
    o vary the color brightness
    o vary the color saturation
    o vary the image hue
    o gamma correct the image
    o sharpen the image contrast
    o dull the image contrast
    o perform histogram equalization on the image
    o perform histogram normalization on the image
    o negate the image colors
    o convert the image to grayscale
    o set the maximum number of unique colors in the image
    o reduce the speckles within an image
    o eliminate peak noise from an image
    o detect edges within the image
    o emboss an image
    o segment the image by color
    o simulate an oil painting
    o simulate a charcoal drawing
    o annotate the image with text
    o draw on the image
    o edit an image pixel color
    o edit the image matte information
    o composite an image with another
    o add a border to the image
    o surround image with an ornamental border
    o add an image comment
    o apply image processing techniques to a region of interest
    o display information about the image
    o show a histogram of the image
    o display image to background of a window
    o set user preferences
    o display information about this program
    o discard all images and exit program
    o change the level of magnification
    o display images specified by a World Wide Web (WWW) uniform resource locator (URL)

EXAMPLES
To scale an image of a cockatoo to exactly 640 pixels in width and 480 pixels in height and position the window at location (200,200), use:
     display -geometry 640x480+200+200! cockatoo.miff
To display an image of a cockatoo without a border centered on a backdrop, use:
     display +borderwidth -backdrop cockatoo.miff
To tile a slate texture onto the root window, use:
     display -size 1280x1024 -window root slate.png
To display a visual image directory of all your JPEG images, use:
     display 'vid:*.jpg'
To display a MAP image that is 640 pixels in width and 480 pixels in height with 256 colors, use:
     display -size 640x480+256 cockatoo.map
To display an image of a cockatoo specified with a World Wide Web (WWW) uniform resource locator (URL), use
     display ftp://wizards.dupont.com/images/cockatoo.jpg

OPTIONS

-backdrop
    display the image centered on a backdrop. This backdrop covers the entire workstation screen and is useful for hiding other X window activity while viewing the image. The color of the backdrop is specified as the background color. Refer to X RESOURCES for details.

-border <width>x<height>
    surround the image with a border of color. See X(1) for details about the geometry specification. The color of the border is obtained from the X server and is defined as bordercolor (class borderColor). See X(1) for details.

-cache threshold
    megabytes of memory available to the pixel cache. Image pixels are stored in memory until 80 megabytes of memory have been consumed. Subsequent pixel operations are cached on disk. Operations to memory are significantly faster but if your computer does not have a sufficient amount of free memory you may want to adjust this threshold value.

-colormap type
    the type of colormap: Shared or Private. This option only applies when the default X server visual is PseudoColor or GrayScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. Choose Private and the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.

-colors value
    preferred number of colors in the image. The actual number of colors in the image may be less than your request, but never more. Note, this is a color reduction option. Images with less unique colors than specified with this option will have any duplicate or unused colors removed. Refer to quantize(9) for more details. Note, options -dither, -colorspace, and -treedepth affect the color reduction algorithm.

-colorspace value
    the type of colorspace: GRAY, OHTA, RGB, Transparent, XYZ, YCbCr, YIQ, YPbPr, YUV, or CMYK. Color reduction, by default, takes place in the RGB color space. Empirical evidence suggests that distances in color spaces such as YUV or YIQ correspond to perceptual color differences more closely than do distances in RGB space. These color spaces may give better results when color reducing an image. Refer to quantize(9) for more details. The Transparent color space behaves uniquely in that it preserves the matte channel of the image if it exists. The -colors or -monochrome option is required for this option to take effect.

-comment string
    annotate an image with a comment. By default, each image is commented with its file name. Use this option to assign a specific comment to the image. Optionally you can include the image filename, type, width, height, or other image attributes by embedding special format characters:
        %b   file size
        %d   directory
        %e   filename extention
        %f   filename
        %h   height
        %i   input filename
        %l   label
        %m   magick
        %n   number of scenes
        %o   output filename
        %p   page number
        %q   quantum depth
        %s   scene number
        %t   top of filename
        %u   unique temporary filename
        %w   width
        %x   x resolution
        %y   y resolution
        \n   newline
        \r   carriage return
    For example,
         -comment "%m:%f %wx%h"
    produces an image comment of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480. If the first character of string is @, the image comment is read from a file titled by the remaining characters in the string.

-compress type
    the type of image compression: None, BZip, Fax, Group4, JPEG, LZW, RunlengthEncoded, or Zip. Use this option with -write to specify the the type of image compression. See miff(5) for details. Specify +compress to store the binary image in an uncompressed format. The default is the compression type of the specified image file.

-contrast
    enhance or reduce the image contrast. This option enhances the intensity differences between the lighter and darker elements of the image. Use -contrast to enhance the image or +contrast to reduce the image contrast.

-crop <width>x<height>{+-}<x offset>{+-}<y offset>{%}
    preferred size and location of the cropped image. See X(1) for details about the geometry specification. To specify a percentage width or height instead, append %. For example to crop the image by ten percent on all sides of the image, use -crop 10%. Use cropping to apply image processing options to, or display, a particular area of an image. Use cropping to crop a particular area of an image. Use -crop 0x0 to trim edges that are the background color. Add an x and y offset to leave a portion of the trimmed edges with the image. The equivalent X resource for this option is cropGeometry (class CropGeometry). See X RESOURCES for details.

-delay <1/100ths of a second>
    display the next image after pausing. This option is useful when viewing several images in sequence. 1/100ths of a second must expire before the next image is displayed. The delay is rounded to the nearest second. The default is to display the image and wait until you choose to display the next image or terminate the program.

-density <width>x<height>
    vertical and horizontal resolution in pixels of the image. This option specifies an image density when decoding a Postscript or Portable Document page. The default is the same as the resolution of your X server (see xdpyinfo(1)). This option is used in concert with -page.

-despeckle
    reduce the speckles within an image.

-display host:display[.screen]
    specifies the X server to contact; see X(1).

-dispose method
    GIF disposal method. Here are the valid methods:
         0     No disposal specified.
         1     Do not dispose between frames.
         2     Overwrite frame with background color from header.
         3     Overwrite with previous frame.

-dither
    apply Floyd/Steinberg error diffusion to the image. The basic strategy of dithering is to trade intensity resolution for spatial resolution by averaging the intensities of several neighboring pixels. Images which suffer from severe contouring when reducing colors can be improved with this option. The -colors or -monochrome option is required for this option to take effect. Use +dither to render Postscript without text or graphic aliasing.

-edge factor
    detect edges with an image. Specify factor as the percent enhancement (0.0 - 99.9%).

-enhance
    apply a digital filter to enhance a noisy image.

-filter value
    use this type of filter when resizing an image. Use this option to affect the resizing operation of an image (see -geometry). Choose from these filters:
         Point
         Box
         Triangle
         Hermite
         Hanning
         Hamming
         Blackman
         Gaussian
         Quadratic
         Cubic
         Catrom
         Mitchell
         Lanczos
         Bessel
         Sinc
    The default filter is Lanczos.

-flip
    create a "mirror image" by reflecting the image scanlines in the vertical direction.

-flop
    create a "mirror image" by reflecting the image scanlines in the horizontal direction.

-frame <width>x<height>+<outer bevel width>+<inner bevel width>
    surround the image with an ornamental border. See X(1) for details about the geometry specification. The color of the border is specified with the -mattecolor command line option.

-gamma value
    level of gamma correction. The same color image displayed on two different workstations may look different due to differences in the display monitor. Use gamma correction to adjust for this color difference. Reasonable values extend from 0.8 to 2.3. You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delineated with slashes (i.e. 1.7/2.3/1.2). Use +gamma to set the image gamma level without actually adjusting the image pixels. This option is useful if the image is of a known gamma but not set as an image attribute (e.g. PNG images).

-geometry <width>x<height>{+-}<x offset>{+-}<y offset>{%}{!}{<}{>}
    preferred size and location of the image window. See X(1) for details about the geometry specification. By default, the window size is the image size and the location is chosen by you when it is mapped. By default, the width and height are maximum values. That is, the image is expanded or contracted to fit the width and height value while maintaining the aspect ratio of the image. Append an exclamation point to the geometry to force the image size to exactly the size you specify. For example, if you specify 640x480! the image width is set to 640 pixels and height to 480. If only one factor is specified, both the width and height assume the value. To specify a percentage width or height instead, append %. The image size is multiplied by the width and height percentages to obtain the final image dimensions. To increase the size of an image, use a value greater than 100 (e.g. 125%). To decrease an image's size, use a percentage less than 100. Use > to change the dimensions of the image only if its size exceeds the geometry specification. < resizes the image only if its dimensions is less than the geometry specification. For example, if you specify 640x480> and the image size is 512x512, the image size does not change. However, if the image is 1024x1024, it is resized to 640x480. When displaying an image on an X server, <x offset> and <y offset> is relative to the root window. The equivalent X resource for this option is geometry (class Geometry). See X RESOURCES for details.

-interlace type
    the type of interlacing scheme: None, Line, Plane, or Partition. The default is None. This option is used to specify the type of interlacing scheme for raw image formats such as RGB or YUV. No means do not interlace (RGBRGBRGBRGBRGBRGB...), Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...). Partition is like plane except the different planes are saved to individual files (e.g. image.R, image.G, and image.B). Use Line, or Plane to create an interlaced GIF or progressive JPEG image.

-immutable
    displayed image cannot be modified",

-label string
    assign a label to an image. Use this option to assign a specific label to the image. Optionally you can include the image filename, type, width, height, or other image attribute in the label by embedding special format characters. See -comment for details. For example,
         -label "%m:%f %wx%h"
    produces an image label of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480. If the first character of string is @, the image label is read from a file titled by the remaining characters in the string. When converting to Postscript, use this option to specify a header string to print above the image. Specify the label font with -font.

-map type
    display image using this Standard Colormap type. Choose from these Standard Colormap types:
        best
        default
        gray
        red
        green
        blue The X server must support the Standard Colormap you choose, otherwise an error occurs. Use list as the type and display(1) searches the list of colormap types in top-to-bottom order until one is located. See xstdcmap(1) for one way of creating Standard Colormaps.

-matte
    store matte channel if the image has one otherwise create an opaque one.

-monochrome
    transform the image to black and white.

-negate
    replace every pixel with its complementary color (white becomes black, yellow becomes blue, etc.). The red, green, and blue intensities of an image are negated. Use +negate to only negate the grayscale pixels of the image.

-page <width>x<height>{+-}<x offset>{+-}<y offset>{%}{!}{<}{>}
    preferred size and location of an image canvas. Use this option to specify the dimensions of the Postscript page in dots per inch or a TEXT page in pixels. The choices for a Postscript page are:
        Letter      612x 792
        Tabloid     792x1224
        Ledger     1224x 792
        Legal       612x1008
        Statement   396x 612
        Executive   540x 720
        A3          842x1190
        A4          595x 842
        A5          420x 595
        B4          729x1032
        B5          516x 729
        Folio       612x 936
        Quarto      610x 780
        10x14       720x1008
    For convenience you can specify the page size by media (e.g. A4, Ledger, etc.). Otherwise, -page behaves much like -geometry (e.g. -page letter+43+43>). To position a GIF image, use -page {+-}<x offset>{+-}<y offset> (e.g. -page +100+200). For a Postscript page, the image is sized as in -geometry and positioned relative to the lower left hand corner of the page by {+-}<x offset>{+-}<y offset>. Use -page 612x792>, for example, to center the image within the page. If the image size exceeds the Postscript page, it is reduced to fit the page. The default page dimensions for a TEXT image is 612x792. This option is used in concert with -density.

-quality value
    JPEG/MIFF/PNG compression level. For the JPEG image format, quality is 0 (worst) to 100 (best). The default quality is 75. Quality for the MIFF and PNG image format sets the amount of image compression (quality / 10) and filter-type (quality % 10). Compression quality values range from 0 (worst) to 100 (best). If filter-type is 4 or less, the specified filter-type is used for all scanlines:
        0: none
        1: sub
        2: up
        3: average
        4: Paeth
    If filter-type is 5, adaptive filtering is used when quality is greater than 50 and the image does not have a color map, otherwise no filtering is used. If filter-type is 6 or more, adaptive filtering with minimum-sum-of-absolute-values is used. The default is quality is 75. Which means nearly the best compression with adaptive filtering. For further information, see the PNG specification (RFC 2083), <http://www.w3.org/pub/WWW/TR>.

-raise <width>x<height>
    lighten or darken image edges to create a 3-D effect. See X(1) for details about the geometry specification. Use -raise to create a raised effect, otherwise use +raise.

-remote string
    execute a command in an remote display process. The only command recognized at this time is the name of an image file to load.

-roll {+-}<x offset>{+-}<y offset>
    roll an image vertically or horizontally. See X(1) for details about the geometry specification. A negative x offset rolls the image left-to-right. A negative y offset rolls the image top-to-bottom.

-rotate degrees{<}{>}
    apply Paeth image rotation to the image. Use > to rotate the image only if its width exceeds the height. < rotates the image only if its width is less than the height. For example, if you specify -90> and the image size is 480x640, the image is not rotated by the specified angle. However, if the image is 640x480, it is rotated by -90 degrees. Empty triangles left over from rotating the image are filled with the color defined as bordercolor (class borderColor).

-sample geometry
    scale image with pixel sampling. See -geometry for details about the geometry specification.

-scene value
    image scene number. Use this option to specify an image sequence with a single filename. See the discussion of file below for details.

-segment value
    eliminate clusters that are insignificant. The number of pixels in each cluster must exceed the the cluster threshold to be considered valid. See IMAGE SEGMENTATION for details.

-sharpen factor
    sharpen an image. Specify factor as the percent enhancement (0.0 - 99.9%).

-size <width>x<height>+<offset>
    width and height of the image. Use this option to specify the width and height of raw images whose dimensions are unknown such as GRAY, RGB, or CMYK. In addition to width and height, use -size to skip any header information in the image or tell the number of colors in a MAP image file, (e.g. -size 640x512+256). For Photo CD images, choose from these sizes:
          192x128
          384x256
          768x512
         1536x1024
         3072x2048
    Finally, use this option to choose a particular resolution layer of a JBIG or JPEG image (e.g. -size 1024x768).

-texture filename
    name of texture to tile onto the image background.

-title string
    assign a title to the displayed image. Use this option to assign a specific title to the image. This is assigned to the image window and is typically displayed in the window title bar. Optionally you can include the image filename, type, width, height, or other image attributes by embedding special format characters. See -comment for details. For example,
         -title "%m:%f %wx%h"
    produces an image title of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

-treedepth value
    Normally, this integer value is zero or one. A zero or one tells display to choose a optimal tree depth for the color reduction algorithm. An optimal depth generally allows the best representation of the source image with the fastest computational speed and the least amount of memory. However, the default depth is inappropriate for some images. To assure the best representation, try values between 2 and 8 for this parameter. Refer to quantize(9) for more details. The -colors or -monochrome option is required for this option to take effect.

-update seconds
    detect when image file is modified and redisplay. Suppose that while you are displaying an image the file that is currently displayed is over-written. display will automatically detect that the input file has been changed and update the displayed image accordingly.

-verbose
    print detailed information about the image. This information is printed: image scene number; image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and transform the image. Refer to miff(5) for a description of the image class. If -colors is also specified, the total unique colors in the image and color reduction error values are printed. Refer to quantize(9) for a description of these values.

-visual type
    display image using this visual type. Choose from these visual classes:
         StaticGray
         GrayScale
         StaticColor
         PseudoColor
         TrueColor
         DirectColor
         default
         visual id
    The X server must support the visual you choose, otherwise an error occurs. If a visual is not specified, the visual class that can display the most simultaneous colors on the default X server screen is chosen.

-window id
    set the background pixmap of this window to the image. id can be a window id or name. Specify root to select X's root window as the target window. By default the image is tiled onto the background of the target window. If -backdrop or -geometry are specified, the image is surrounded by the background color. Refer to X RESOURCES for details. The image will not display on the root window if the image has more unique colors than the target window colormap allows. Use -colors to reduce the number of colors. -window_group id exit program when this window id is destroyed. id can be a window id or name.

-write filename
    write image to a file. If file already exists, you will be prompted as to whether it should be overwritten. By default, the image is written in the format that it was read in as. To specify a particular image format, prefix file with the image type and a colon (i.e. ps:image) or specify the image type as the filename suffix (i.e. image.ps). See convert(1) for a list of valid image formats. Specify file as - for standard output. If file has the extension .Z or .gz, the file size is compressed using with compress or gzip respectively. Precede the image file name | to pipe to a system command. If file already exists, you will be prompted as to whether it should be overwritten. Use -compress to specify the type of image compression. The equivalent X resource for this option is writeFilename (class WriteFilename). See X RESOURCES for details.

In addition to those listed above, you can specify these standard X resources as command line options: -background, -bordercolor, -borderwidth, -font, -foreground, -iconGeometry, -iconic, -mattecolor, -name, or -title. See X RESOURCES for details. Options are processed in command line order. Any option you specify on the command line remains in effect until it is explicitly changed by specifying the option again with a different effect. For example to display two images, the first with 32 colors, and the second with only 16 colors, use:
     display -colors 32 cockatoo.miff -colors 16 macaw.miff
By default, the image format is determined by its magic number. To specify a particular image format, precede the filename with an image format name and a colon (i.e. ps:image) or specify the image type as the filename suffix (i.e. image.ps). See convert(1) for a list of valid image formats. When you specify X as your image type, the filename has special meaning. It specifies an X window by id, name, or root. If no filename is specified, the window is selected by clicking the mouse in the desired window. Specify file as - for standard input. If file has the extension .Z or .gz, the file is uncompressed with uncompress or gunzip respectively. Precede the image file name | to pipe from a system command. Use an optional index enclosed in brackets after a file name to specify a desired subimage of a multi-resolution image format like Photo CD (e.g. img0001.pcd[4]) or a range for MPEG images (e.g. video.mpg[50-75]). A subimage specification can be disjoint (e.g. image.tiff[2,7,4]). For raw images, specify a subimage with a geometry (e.g. -size 640x512 image.rgb[320x256+50+50]). Single images are read with the filename you specify. Alternatively, you can display an image sequence with a single filename. Define the range of the image sequence with -scene. Each image in the range is read with the filename followed by a period (.) and the scene number. You can change this behavior by embedding a printf format specification in the file name. For example,
     -scene 0-9 image%02d.miff
displays files image00.miff, image01.miff, through image09.miff.

BUTTONS
The effects of each button press is described below. Three buttons are required. If you have a two button mouse, button 1 and 3 are returned. Press ALT and button 3 to simulate button 2.

1   Press this button to map or unmap the Command widget. See the next section for more information about the Command widget.

2   Press and drag to define a region of the image to magnify.

3   Press and drag to choose from a select set of display(1) commands. This button behaves differently if the image being displayed is a visual image directory. Here, choose a particular tile of the directory and press this button and drag to select a command from a pop-up menu. Choose from these menu items:
        Open
        Next
        Former
        Delete
        Update
    If you choose Open, the image represented by the tile is displayed. To return to the visual image directory, choose Next from the Command widget (refer to COMMAND WIDGET). Next and Former moves to the next or former image respectively. Choose Delete to delete a particular image tile. Finally, choose Update to synchronize all the image tiles with their respective images. See montage(1) and miff(5) for more details.

COMMAND WIDGET
The Command widget lists a number of sub-menus and commands. They are
    File
      Open...
      Next
      Former
      Select...
      Save...
      Print...
      Delete...
      Canvas...
      Visual Directory...
      Quit
    Edit
      Undo
      Redo
      Cut
      Copy
      Paste
    View
      Half Size
      Original Size
      Double Size
      Resize...
      Apply
      Refresh
      Restore
    Transform
      Crop
      Chop
      Flop
      Flip
      Rotate Right
      Rotate Left
      Rotate...
      Shear...
      Roll...
      Trim Edges
    Enhance
      Hue...
      Saturation...
      Brightness...
      Gamma...
      Spiff...
      Dull
      Equalize
      Normalize
      Negate
      Grayscale
      Map...
      Quantize...
    Effects
      Despeckle
      Emboss
      Reduce Noise
      Add Noise
      Sharpen...
      Blur...
      Threshold...
      Edge Detect...
      Spread...
      Shade...
      Raise...
      Segment...
    F/X
      Solarize...
      Swirl...
      Implode...
      Wave...
      Oil Painting...
      Charcoal Drawing...
    Image Edit
      Annotate...
      Draw...
      Color...
      Matte...
      Composite...
      Add Border...
      Add Frame...
      Comment...
      Launch...
      Region of Interest...
    Miscellany
      Image Info
      Zoom Image
      Show Preview...
      Show Histogram
      Show Matte
      Background...
      Slide Show
      Preferences...
    Help
      Help
      Browse Documentation
      About Display
Menu items with a indented triangle have a sub-menu. They are represented above as the indented items. To access a sub-menu item, move the pointer to the appropriate menu and press button 1 and drag. When you find the desired sub-menu item, release the button and the command is executed. Move the pointer away from the sub-menu if you decide not to execute a particular command.

KEYBOARD ACCELERATORS
Accelerators are one or two key presses that effect a particular command. The keyboard accelerators that display(1) understands is:

Ctl+O
    Press to load an image from a file. Refer to IMAGE LOADING for more details.

space
    Press to display the next image. If the image is a multi-paged document such as a Postscript document, you can skip ahead several pages by preceeding this command with a number. For example to display the fourth page beyond the current page, press 4space.

backspace
    Press to display the former image. If the image is a multi-paged document such as a Postscript document, you can skip behind several pages by preceeding this command with a number. For example to display the fourth page preceeding the current page, press 4n.

Ctl+S
    Press to save the image to a file.

Ctl+P
    Press to print the image to a Postscript printer.

Ctl+D
    Press to delete an image file.

Ctl+N
    Press to create a blank canvas.

Ctl+Q
    Press to discard all images and exit program.

Ctl+Z
    Press to undo last image transformation.

Ctl+R
    Press to redo last image transformation.

Ctl+X
    Press to cut a region of the image. Refer to IMAGE CUTTING for more details.

Ctl+C
    Press to copy a region of the image. Refer to IMAGE COPYING for more details.

Ctl+V
    Press to paste a region to the image. Refer to IMAGE PASTING for more details.

<   Press to half the image size.

-   Press to return to the original image size.

>   Press to double the image size.

%   Press to resize the image to a width and height you specify.

Cmd-A
    Press to make any image transformations permanent. By default, any image size transformations are applied to the original image to create the image displayed on the X server. However, the transformations are not permanent (i.e. the original image does not change size only the X image does). For example, if you press > the X image will appear to double in size, but the original image will in fact remain the same size. To force the original image to double in size, press > followed by A.

@   Press to refresh the image window.

C   Press to crop the image. Refer to IMAGE CROPPING for more details.

[   Press to chop the image. Refer to IMAGE CHOPPING for more details.

H   Press to flop image in the horizontal direction.

V   Press to flip image in the vertical direction.

/   Press to rotate the image 90 degrees clockwise.

    Press to rotate the image 90 degrees counter-clockwise.

*   Press to rotate the image the number of degrees you specify. Refer to IMAGE ROTATION for more details.

s   Press to shear the image the number of degrees you specify.

r   Press to roll the image.

t   Press to trim the image edges.

Shft-H
    Press to vary the color hue.

Shft-S
    Press to vary the color saturation.

Shft-L
    Press to vary the image brightness.

Shft-G
    Press to gamma correct the image.

Shft-C
    Press to spiff up the image contrast.

Shft-Z
    Press to dull the image contrast.

=   Press to perform histogram equalization on the image.

Shft-N
    Press to perform histogram normalization on the image.

~   Press to negate the colors of the image.

.   Press to convert the image colors to gray.

#   Press to set the maximum number of unique colors in the image.

F2  Press to reduce the speckles in an image.

F3  Press to emboss an image.

F4  Press to eliminate peak noise from an image.

F5  Press to add noise to an image.

F6  Press to sharpen an image.

F7  Press to blur image an image.

F8  Press to threshold the image.

F9  Press to detect edges within an image.

F10 Press to displace pixels by a random amount.

F11 Press to shade the image using a distant light source.

F12 Press to lighten or darken image edges to create a 3-D effect.

F13 Press to segment the image by color.

Meta-S
    Press to swirl image pixels about the center.

Meta-I
    Press to implode image pixels about the center.

Meta-W
    Press to alter an image along a sine wave.

Meta-P
    Press to simulate an oil painting.

Meta-C
    Press to simulate a charcoal drawing.

Alt-A
    Press to annotate the image with text. Refer to IMAGE ANNOTATION for more details.

Alt-D
    Press to draw a line on the image. Refer to IMAGE DRAWING for more details.

Alt-P
    Press to edit an image pixel color. Refer to COLOR EDITING for more details.

Alt-M
    Press to edit the image matte information. Refer to MATTE EDITING for more details.

Alt-V
    Press to composite the image with another. Refer to IMAGE COMPOSITING for more details.

Alt-B
    Press to add a border to the image.

Alt-F
    Press to add a ornamental frame to the image.

Shft-!
    Press to add an image comment.

Ctl-A
    Press to apply an image processing technique to a region of interest. Refer to REGION OF INTEREST for more details.

Shft-?
    Press to display information about the image.

Shft-+
    Press to map the zoom image window.

Shft-P
    Press to preview an image enhancement, effect, or f/x.

F1  Press to display helpful information about display(1).

Find
    Press to browse documentation about ImageMagick.

1-9 Press to change the level of magnification. Use the arrow keys to move the image one pixel up, down, left, or right within the magnify window. Be sure to first map the magnify window by pressing button 2. Press ALT and one of the arrow keys to trim off one pixel from any side of the image.

X RESOURCES
Display options can appear on the command line or in your X resource file. Options on the command line supersede values specified in your X resource file. See X(1) for more information on X resources. Most display options have a corresponding X resource. In addition, display uses the following X resources:

background (class Background)
    Specifies the preferred color to use for the image window background. The default is #ccc.

borderColor (class BorderColor)
    Specifies the preferred color to use for the image window border. The default is #ccc.

borderWidth (class BorderWidth)
    Specifies the width in pixels of the image window border. The default is 2.

browseCommand (class browseCommand)
    Specifies the name of the preferred browser when displaying ImageMagick documentation. The default is netscape %s.

confirmExit (class ConfirmExit)
    Display pops up a dialog box to confirm exiting the program when exiting the program. Set this resource to False to exit without a confirmation.

displayGamma (class DisplayGamma)
    Specifies the gamma of your X server. You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delineated with slashes (i.e. 1.7/2.3/1.2). The default is 2.2.

displayWarnings (class DisplayWarnings)
    Display pops up a dialog box whenever a warning message occurs. Set this resource to False to ignore warning messages.

editorCommand (class editorCommand)
    Specifies the name of the preferred editor when editing image comments. The default is xterm -title "Edit Image Comment" -e vi %s.

font (class FontList)
    Specifies the name of the preferred font to use in normal formatted text. The default is 14 point Helvetica.

font[1-9] (class Font[1-9])
    Specifies the name of the preferred font to use when annotating the image window with text. The default fonts are fixed, variable, 5x8, 6x10, 7x13bold, 8x13bold, 9x15bold, 10x20, and 12x24. Refer to IMAGE ANNOTATION for more details.

foreground (class Foreground)
    Specifies the preferred color to use for text within the image window. The default is black.

gammaCorrect (class gammaCorrect)
    This resource, if true, will lighten or darken an image of known gamma to match the gamma of the display (see resource displayGamma). The default is True.

geometry (class Geometry)
    Specifies the preferred size and position of the image window. It is not necessarily obeyed by all window managers.

iconGeometry (class IconGeometry)
    Specifies the preferred size and position of the application when iconified. It is not necessarily obeyed by all window managers.

iconic (class Iconic)
    This resource indicates that you would prefer that the application's windows initially not be visible as if the windows had be immediately iconified by you. Window managers may choose not to honor the application's request.

magnify (class Magnify)
    specifies an integral factor by which the image should be enlarged. The default is 3. This value only affects the magnification window which is invoked with button number 3 after the image is displayed. Refer to BUTTONS for more details.

matteColor (class MatteColor)
    Specify the color of windows. It is used for the backgrounds of windows, menus, and notices. A 3D effect is achieved by using highlight and shadow colors derived from this color. Default value: #ccc.

name (class Name)
    This resource specifies the name under which resources for the application should be found. This resource is useful in shell aliases to distinguish between invocations of an application, without resorting to creating links to alter the executable file name. The default is the application name.

pen[1-9] (class Pen[1-9])
    Specifies the color of the preferred font to use when annotating the image window with text. The default colors are black, blue, green, cyan, gray, red, magenta, yellow, and white. Refer to IMAGE ANNOTATION for more details.

printCommand (class PrintCommand)
    This command is executed whenever Print is issued (see BUTTONS. In general, it is the command to print Postscript to your printer. Default value: lp -c -s %i.

sharedMemory (class SharedMemory)
    This resource specifies whether display should attempt use shared memory for pixmaps. ImageMagick must be compiled with shared memory support, and the display must support the MIT-SHM extension. Otherwise, this resource is ignored. The default is True.

textFont (class textFont)
    Specifies the name of the preferred font to use in fixed (typewriter style) formatted text. The default is 14 point Courier.

title (class Title)
    This resource specifies the title to be used for the image window. This information is sometimes used by a window manager to provide a header identifying the window. The default is the image file name.

undoCache (class UndoCache)
    Specifies, in mega-bytes, the amount of memory in the undo edit cache. Each time you modify the image it is saved in the undo edit cache as long as memory is available. You can subsequently undo one or more of these transformations. The default is 16 mega-bytes.

usePixmap (class UsePixmap)
    Images are maintained as a XImage by default. Set this resource to True to utilize a server Pixmap instead. This option is useful if your image exceeds the dimensions of your server screen and you intend to pan the image. Panning is much faster with Pixmaps than with a XImage. Pixmaps are considered a precious resource, use them with discretion. To set the geometry of the Magnify or Pan or window, use the geometry resource. For example, to set the Pan window geometry to 256x256, use:
         display.pan.geometry: 256x256

IMAGE LOADING
To select an image to display, choose Open of the File sub-menu from the Command widget. A file browser is displayed. To choose a particular image file, move the pointer to the filename and press any button. The filename is copied to the text window. Next, press Open or press the RETURN key. Alternatively, you can type the image file name directly into the text window. To descend directories, choose a directory name and press the button twice quickly. A scrollbar allows a large list of filenames to be moved through the viewing area if it exceeds the size of the list area. You can trim the list of file names by using shell globbing characters. For example, type *.jpg to list only files that end with .jpg. To select your image from the X server screen instead of from a file, Choose Grab of the Open widget.

VISUAL IMAGE DIRECTORY
To create a Visual Image Directory, choose Visual Directory of the File sub-menu from the Command widget. A file browser is displayed. To create a Visual Image Directory from all the images in the current directory, press Directory or press the RETURN key. Alternatively, you can select a set of image names by using shell globbing characters. For example, type *.jpg to include only files that end with .jpg. To descend directories, choose a directory name and press the button twice quickly. A scrollbar allows a large list of filenames to be moved through the viewing area if it exceeds the size of the list area. After you select a set of files, they are turned into thumbnails and tiled onto a single image. Now move the pointer to a particular thumbnail and press button 3 and drag. Finally, select Open. The image represented by the thumbnail is displayed at its full size. Choose Next from the File sub-menu of the Command widget to return to the Visual Image Directory.

IMAGE CUTTING
Note that cut information for image window is not retained for colormapped X server visuals (e.g. StaticColor, StaticColor, GrayScale, PseudoColor). Correct cutting behavior may require a TrueColor or DirectColor visual or a Standard Colormap. To begin, press choose Cut of the Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press F3 in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in cut mode. In cut mode, the Command widget has these options:
    Help
    Dismiss
To define a cut region, press button 1 and drag. The cut region is defined by a highlighted rectangle that expands or contracts as it follows the pointer. Once you are satisfied with the cut region, release the button. You are now in rectify mode. In rectify mode, the Command widget has these options:
    Cut
    Help
    Dismiss
You can make adjustments by moving the pointer to one of the cut rectangle corners, pressing a button, and dragging. Finally, press Cut to commit your copy region. To exit without cutting the image, press Dismiss.

IMAGE COPYING
To begin, press choose Copy of the Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press F4 in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in copy mode. In copy mode, the Command widget has these options:
    Help
    Dismiss
To define a copy region, press button 1 and drag. The copy region is defined by a highlighted rectangle that expands or contracts as it follows the pointer. Once you are satisfied with the copy region, release the button. You are now in rectify mode. In rectify mode, the Command widget has these options:
    Copy
    Help
    Dismiss
You can make adjustments by moving the pointer to one of the copy rectangle corners, pressing a button, and dragging. Finally, press Copy to commit your copy region. To exit without copying the image, press Dismiss.

IMAGE PASTING
To begin, press choose Paste of the Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press F5 in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in Paste mode. To exit immediately, press Dismiss. In Paste mode, the Command widget has these options:
    Operators
      Over
      In
      Out
      Atop
      Xor
      Plus
      Minus
      Add
      Subtract
      Difference
      Bumpmap
      Replace
      ReplaceRed
      ReplaceGreen
      ReplaceBlue
      ReplaceMatte
    Help
    Dismiss
Choose a composite operation from the Operators sub-menu of the Command widget. How each operator behaves is described below. image window is the image currently displayed on your X server and image is the image obtained with the File Browser widget.

Over
    The result is the union of the two image shapes, with image obscuring image window in the region of overlap.

In  The result is simply image cut by the shape of image window. None of the image data of image window is in the result.

Out The resulting image is image with the shape of image window cut out.

Atop
    The result is the same shape as image image window, with image obscuring image window where the image shapes overlap. Note this differs from over because the portion of image outside image window's shape does not appear in the result.

Xor The result is the image data from both image and image window that is outside the overlap region. The overlap region is blank.

Plus
    The result is just the sum of the image data. Output values are cropped to 255 (no overflow). This operation is independent of the matte channels.

Minus
    The result of image - image window, with underflow cropped to zero. The matte channel is ignored (set to 255, full coverage).

Add The result of image + image window, with overflow wrapping around (mod 256).

Subtract
    The result of image - image window, with underflow wrapping around (mod 256). The add and subtract operators can be used to perform reversible transformations.

Difference
    The result of abs(image - image window). This is useful for comparing two very similar images.

Bumpmap
    The result of image window shaded by image.

Replace
    The resulting image is image window replaced with image. Here the matte information is ignored.

ReplaceRed
    The resulting image is the red layer of image window replaced with the red layer of image. The remaining layers remain untouched.

ReplaceGreen
    The resulting image is the green layer of image window replaced with the green layer of image. The remaining layers remain untouched.

ReplaceBlue
    The resulting image is the blue layer of image window replaced with the blue layer of image. The remaining layers remain untouched.

ReplaceMatte
    The resulting image is the matte layer of image window replaced with the matte layer of image. The remaining layers remain untouched. The image compositor requires a matte, or alpha channel in the image for some operations. This extra channel usually defines a mask which represents a sort of a cookie-cutter for the image. This is the case when matte is 255 (full coverage) for pixels inside the shape, zero outside, and between zero and 255 on the boundary. If image does not have a matte channel, it is initialized with 0 for any pixel matching in color to pixel location (0,0), otherwise 255. See MATTE EDITING for a method of defining a matte channel. Note that matte information for image window is not retained for colormapped X server visuals (e.g. StaticColor, StaticColor, GrayScale, PseudoColor). Correct compositing behavior may require a TrueColor or DirectColor visual or a Standard Colormap. Choosing a composite operator is optional. The default operator is replace. However, you must choose a location to composite your image and press button 1. Press and hold the button before releasing and an outline of the image will appear to help you identify your location. The actual colors of the pasted image is saved. However, the color that appears in image window may be different. For example, on a monochrome screen image window will appear black or white even though your pasted image may have many colors. If the image is saved to a file it is written with the correct colors. To assure the correct colors are saved in the final image, any PseudoClass image is promoted to DirectClass (see miff(5)). To force a PseudoClass image to remain PseudoClass, use -colors.

IMAGE CROPPING
To begin, press choose Crop of the Transform sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press [ in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in crop mode. In crop mode, the Command widget has these options:
    Help
    Dismiss
To define a cropping region, press button 1 and drag. The cropping region is defined by a highlighted rectangle that expands or contracts as it follows the pointer. Once you are satisfied with the cropping region, release the button. You are now in rectify mode. In rectify mode, the Command widget has these options:
    Crop
    Help
    Dismiss
You can make adjustments by moving the pointer to one of the cropping rectangle corners, pressing a button, and dragging. Finally, press Crop to commit your cropping region. To exit without cropping the image, press Dismiss.

IMAGE CHOPPING
An image is chopped interactively. There is no command line argument to chop an image. To begin, choose Chop of the Transform sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press ] in the image window (see KEYBOARD ACCELERATORS). You are now in Chop mode. To exit immediately, press Dismiss. In Chop mode, the Command widget has these options:
    Direction
      horizontal
      vertical
    Help
    Dismiss
If the you choose the horizontal direction (this is the default), the area of the image between the two horizontal endpoints of the chop line is removed. Otherwise, the area of the image between the two vertical endpoints of the chop line is removed. Select a location within the image window to begin your chop, press and hold any button. Next, move the pointer to another location in the image. As you move a line will connect the initial location and the pointer. When you release the button, the area within the image to chop is determined by which direction you choose from the Command widget. To cancel the image chopping, move the pointer back to the starting point of the line and release the button.

IMAGE ROTATION
Press the / key to rotate the image 90 degrees or \ to rotate -90 degrees (see KEYBOARD ACCELERATORS). To interactively choose the degree of rotation, choose Rotate... of the Pixel Transform submenu from the Command Widget (see COMMAND WIDGET). Alternatively, press * in the image window (see KEYBOARD ACCELERATORS). A small horizontal line is drawn next to the pointer. You are now in rotate mode. To exit immediately, press Dismiss. In rotate mode, the Command widget has these options:
    Pixel Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      Browser...
    Direction
      horizontal
      vertical
    Crop
      false
      true
    Sharpen
      false
      true
    Help
    Dismiss
Choose a background color from the Pixel Color sub-menu. Additional background colors can be specified with the color browser. You can change the menu colors by setting the X resources pen1 through pen9. Refer to X RESOURCES for more details. If you choose the color browser and press Grab, you can select the background color by moving the pointer to the desired color on the screen and press any button. The transparent color updates the image matte channel and is useful for image compositing. Choose a point in the image window and press this button and hold. Next, move the pointer to another location in the image. As you move a line connects the initial location and the pointer. When you release the button, the degree of image rotation is determined by the slope of the line you just drew. The slope is relative to the direction you choose from the Direction sub-menu of the Command widget. To cancel the image rotation, move the pointer back to the starting point of the line and release the button.

IMAGE ANNOTATION
An image is annotated interactively. There is no command line argument to annotate an image. To begin, choose Annotate of the Image Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press a in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in annotate mode. To exit immediately, press Dismiss. In annotate mode, the Command widget has these options:
    Font Name
      fixed
      variable
      5x8
      6x10
      7x13bold
      8x13bold
      9x15bold
      10x20
      12x24
      Browser...
    Font Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      transparent
      Browser...
    Box Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      transparent
      Browser...
    Rotate Text
      -90
      -45
      -30
      0
      30
      45
      90
      180
      Dialog...
    Help
    Dismiss
Choose a font name from the Font Name sub-menu. Additional font names can be specified with the font browser. You can change the menu names by setting the X resources font1 through font9. Refer to X RESOURCES for more details. Choose a font color from the Font Color sub-menu. Additional font colors can be specified with the color browser. You can change the menu colors by setting the X resources pen1 through pen9. Refer to X RESOURCES for more details. If you select the color browser and press Grab, you can choose the font color by moving the pointer to the desired color on the screen and press any button. If you choose to rotate the text, choose Rotate Text from the menu and select an angle. Typically you will only want to rotate one line of text at a time. Depending on the angle you choose, subsequent lines may end up overwriting each other. Choosing a font and its color is optional. The default font is fixed and the default color is black. However, you must choose a location to begin entering text and press button 1. An underscore character will appear at the location of the pointer. The cursor changes to a pencil to indicate you are in text mode. To exit immediately, press Dismiss. In text mode, any key presses will display the character at the location of the underscore and advance the underscore cursor. Enter your text and once completed press Dismiss to finish your image annotation. To correct errors press BACK SPACE. To delete an entire line of text, press DELETE. Any text that exceeds the boundaries of the image window is automatically continued onto the next line. The actual color you request for the font is saved in the image. However, the color that appears in your image window may be different. For example, on a monochrome screen the text will appear black or white even if you choose the color red as the font color. However, the image saved to a file with -write is written with red lettering. To assure the correct color text in the final image, any PseudoClass image is promoted to DirectClass (see miff(5)). To force a PseudoClass image to remain PseudoClass, use -colors.

IMAGE COMPOSITING
An image composite is created interactively. There is no command line argument to composite an image. To begin, choose Composite of the Image Edit from the Command widget (see COMMAND WIDGET). Alternatively, press x in the image window (see KEYBOARD ACCELERATORS). First a popup window is displayed requesting you to enter an image name. Press Composite, Grab or type a file name. Press Cancel if you choose not to create a composite image. When you choose Grab, move the pointer to the desired window and press any button. If the Composite image does not have any matte information, you are informed and the file browser is displayed again. Enter the name of a mask image. The image is typically grayscale and the same size as the composite image. If the image is not grayscale, it is converted to grayscale and the resulting intensities are used as matte information. A small window appears showing the location of the cursor in the image window. You are now in composite mode. To exit immediately, press Dismiss. In composite mode, the Command widget has these options:
    Operators
      over
      in
      out
      atop
      xor
      plus
      minus
      add
      subtract
      difference
      bumpmap
      replace
    Blend
    Displace
    Help
    Dismiss
Choose a composite operation from the Operators sub-menu of the Command widget. How each operator behaves is described below. image window is the image currently displayed on your X server and image is the image obtained with the File Browser widget.

over
    The result is the union of the two image shapes, with image obscuring image window in the region of overlap.

in  The result is simply image cut by the shape of image window. None of the image data of image window is in the result.

out The resulting image is image with the shape of image window cut out.

atop
    The result is the same shape as image image window, with image obscuring image window where the image shapes overlap. Note this differs from over because the portion of image outside image window's shape does not appear in the result.

xor The result is the image data from both image and image window that is outside the overlap region. The overlap region is blank.

plus
    The result is just the sum of the image data. Output values are cropped to 255 (no overflow). This operation is independent of the matte channels.

minus
    The result of image - image window, with underflow cropped to zero. The matte channel is ignored (set to 255, full coverage).

add The result of image + image window, with overflow wrapping around (mod 256).

subtract
    The result of image - image window, with underflow wrapping around (mod 256). The add and subtract operators can be used to perform reversible transformations.

difference
    The result of abs(image - image window). This is useful for comparing two very similar images.

bumpmap
    The result of image window shaded by image.

replace
    The resulting image is image window replaced with image. Here the matte information is ignored. The image compositor requires a matte, or alpha channel in the image for some operations. This extra channel usually defines a mask which represents a sort of a cookie-cutter for the image. This is the case when matte is 255 (full coverage) for pixels inside the shape, zero outside, and between zero and 255 on the boundary. If image does not have a matte channel, it is initialized with 0 for any pixel matching in color to pixel location (0,0), otherwise 255. See MATTE EDITING for a method of defining a matte channel. If you choose blend, the composite operator becomes over. The image matte channel percent transparency is initialized to factor. The image window is initialized to (100-factor). Where factor is the value you specify in the Dialog widget. Displace shifts the image pixels as defined by a displacement map. With this option, image is used as a displacement map. Black, within the displacement map, is a maximum positive displacement. White is a maximum negative displacement and middle gray is neutral. The displacement is scaled to determine the pixel shift. By default, the displacement applies in both the horizontal and vertical directions. However, if you specify a mask, image is the horizontal X displacement and mask the vertical Y displacement. Note that matte information for image window is not retained for colormapped X server visuals (e.g. StaticColor, StaticColor, GrayScale, PseudoColor). Correct compositing behavior may require a TrueColor or DirectColor visual or a Standard Colormap. Choosing a composite operator is optional. The default operator is replace. However, you must choose a location to composite your image and press button 1. Press and hold the button before releasing and an outline of the image will appear to help you identify your location. The actual colors of the composite image is saved. However, the color that appears in image window may be different. For example, on a monochrome screen image window will appear black or white even though your composited image may have many colors. If the image is saved to a file it is written with the correct colors. To assure the correct colors are saved in the final image, any PseudoClass image is promoted to DirectClass (see miff(5)). To force a PseudoClass image to remain PseudoClass, use -colors.

COLOR EDITING
Changing the the color of a set of pixels is performed interactively. There is no command line argument to edit a pixel. To begin, choose Color from the Image Edit submenu of the Command widget (see COMMAND WIDGET). Alternatively, press c in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in color edit mode. To exit immediately, press Dismiss. In color edit mode, the Command widget has these options:
    Method
      point
      replace
      floodfill
      filltoborder
      reset
    Pixel Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      Browser...
    Border Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      Browser...
    Fuzz
      0
      2
      4
      8
      16
      Dialog...
    Undo
    Help
    Dismiss
Choose a color editing method from the Method sub-menu of the Command widget. The point method recolors any pixel selected with the pointer unless the button is released. The replace method recolors any pixel that matches the color of the pixel you select with a button press. Floodfill recolors any pixel that matches the color of the pixel you select with a button press and is a neighbor. Whereas filltoborder recolors any neighbor pixel that is not the border color. Finally reset changes the entire image to the designated color. Next, choose a pixel color from the Pixel Color sub-menu. Additional pixel colors can be specified with the color browser. You can change the menu colors by setting the X resources pen1 through pen9. Refer to X RESOURCES for more details. Now press button 1 to select a pixel within the image window to change its color. Additional pixels may be recolored as prescribed by the method you choose. If the Magnify widget is mapped, it can be helpful in positioning your pointer within the image (refer to button 2). Alternatively you can select a pixel to recolor from within the Magnify widget. Move the pointer to the Magnify widget and position the pixel with the cursor control keys. Finally, press a button to recolor the selected pixel (or pixels). The actual color you request for the pixels is saved in the image. However, the color that appears in your image window may be different. For example, on a monochrome screen the pixel will appear black or white even if you choose the color red as the pixel color. However, the image saved to a file with -write is written with red pixels. To assure the correct color text in the final image, any PseudoClass image is promoted to DirectClass (see miff(5)). To force a PseudoClass image to remain PseudoClass, use -colors.

MATTE EDITING
Matte information within an image is useful for some operations such as image compositing (See IMAGE COMPOSITING). This extra channel usually defines a mask which represents a sort of a cookie-cutter for the image. This is the case when matte is 255 (full coverage) for pixels inside the shape, zero outside, and between zero and 255 on the boundary. Setting the matte information in an image is done interactively. There is no command line argument to edit a pixel. To begin, and choose Matte of the Image Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press m in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in matte edit mode. To exit immediately, press Dismiss. In matte edit mode, the Command widget has these options:
    Method
      point
      replace
      floodfill
      filltoborder
      reset
    Border Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      Browser...
    Fuzz
      0
      2
      4
      8
      16
      Dialog...
    Matte
    Undo
    Help
    Dismiss
Choose a matte editing method from the Method sub-menu of the Command widget. The point method changes the matte value of the any pixel selected with the pointer until the button is released. The replace method changes the matte value of any pixel that matches the color of the pixel you select with a button press. Floodfill changes the matte value of any pixel that matches the color of the pixel you select with a button press and is a neighbor. Whereas filltoborder changes the matte value of any neighbor pixel that is not the border color. Finally reset changes the entire image to the designated matte value. Choose Matte Value and a dialog appears requesting a matte value. Enter a value between 0 and 255. This value is assigned as the matte value of the selected pixel or pixels. Now, press any button to select a pixel within the image window to change its matte value. If the Magnify widget is mapped, it can be helpful in positioning your pointer within the image (refer to button 2). Alternatively you can select a pixel to change the matte value from within the Magnify widget. Move the pointer to the Magnify widget and position the pixel with the cursor control keys. Finally, press a button to change the matte value of the selected pixel (or pixels). Matte information is only valid in a DirectClass image. Therefore, any PseudoClass image is promoted to DirectClass (see miff(5)). Note that matte information for PseudoClass is not retained for colormapped X server visuals (e.g. StaticColor, StaticColor, GrayScale, PseudoColor) unless you immediately save your image to a file (refer to Write). Correct matte editing behavior may require a TrueColor or DirectColor visual or a Standard Colormap.

IMAGE DRAWING
An image is drawn upon interactively. There is no command line argument to draw on an image. To begin, choose Draw of the Image Edit sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press d in the image window (see KEYBOARD ACCELERATORS). The cursor changes to a crosshair to indicate you are in draw mode. To exit immediately, press Dismiss. In draw mode, the Command widget has these options:
    Primitive
      point
      line
      rectangle
      fill rectangle
      circle
      fill circle
      ellipse
      fill ellipse
      polygon
      fill polygon
    Color
      black
      blue
      cyan
      green
      gray
      red
      magenta
      yellow
      white
      transparent
      Browser...
    Stipple",
      Brick",
      Diagonal",
      Scales",
      Vertical",
      Wavy",
      Translucent",
      Opaque",
      Open...",
    Width
      1
      2
      4
      8
      16
      Dialog...
    Undo
    Help
    Dismiss
Choose a drawing primitive from the Primitive sub-menu. Next, choose a color from the Color sub-menu. Additional colors can be specified with the color browser. You can change the menu colors by setting the X resources pen1 through pen9. Refer to X RESOURCES for more details. If you choose the color browser and press Grab, you can select the primitive color by moving the pointer to the desired color on the screen and press any button. The transparent color updates the image matte channel and is useful for image compositing., Choose a stipple, if appropriate, from the Stipple sub-menu. Additional stipples can be specified with the file browser. Stipples obtained from the file browser must be on disk in the X11 bitmap format. Choose a line width from the Width sub-menu. To choose a specific width select the Dialog widget. Choose a point in the image window and press button 1 and hold. Next, move the pointer to another location in the image. As you move, a line connects the initial location and the pointer. When you release the button, the image is updated with the primitive you just drew. For polygons, the image is updated when you press and release the button without moving the pointer. To cancel image drawing, move the pointer back to the starting point of the line and release the button.

REGION OF INTEREST
To begin, press choose Region of Interest of the Transform sub-menu from the Command widget (see COMMAND WIDGET). Alternatively, press R in the image window (see KEYBOARD ACCELERATORS). A small window appears showing the location of the cursor in the image window. You are now in region of interest mode. In region of interest mode, the Command widget has these options:
    Help
    Dismiss
To define a region of interest, press button 1 and drag. The region of interest is defined by a highlighted rectangle that expands or contracts as it follows the pointer. Once you are satisfied with the region of interest, release the button. You are now in apply mode. In apply mode the Command widget has these options:
    File
      Save...
      Print...
    Edit
      Undo
      Redo
    Transform
      Flip
      Flop
      Rotate Right
      Rotate Left
    Enhance
      Hue...
      Saturation...
      Brightness...
      Gamma...
      Spiff
      Dull
      Equalize
      Normalize
      Negate
      Grayscale
      Quantize...
    Effects
      Despeckle
      Emboss
      Reduce Noise
      Add Noise
      Sharpen...
      Blur...
      Threshold...
      Edge Detect...
      Spread...
      Shade...
      Raise...
      Segment...
    F/X
      Swirl...
      Implode...
      Wave...
      Oil Painting...
      Charcoal Drawing...
    Miscellany
      Image Info
      Zoom Image
      Show Preview...
      Show Histogram
      Show Matte
    Help
    Dismiss
You can make adjustments to the region of interest by moving the pointer to one of the rectangle corners, pressing a button, and dragging. Finally, choose an image processing technique from the Command widget. You can choose more than one image processing technique to apply to an area. Alternatively, you can move the region of interest before applying another image processing technique. To exit, press Dismiss.

IMAGE PANNING
When an image exceeds the width or height of the X server screen, display maps a small panning icon. The rectangle within the panning icon shows the area that is currently displayed in the the image window. To pan about the image, press any button and drag the pointer within the panning icon. The pan rectangle moves with the pointer and the image window is updated to reflect the location of the rectangle within the panning icon. When you have selected the area of the image you wish to view, release the button. Use the arrow keys to pan the image one pixel up, down, left, or right within the image window. The panning icon is withdrawn if the image becomes smaller than the dimensions of the X server screen.

IMAGE SEGMENTATION
Use -segment to segment an image by analyzing the histograms of the color components and identifying units that are homogeneous with the fuzzy c-means technique. The scale-space filter analyzes the histograms of the three color components of the image and identifies a set of classes. The extents of each class is used to coarsely segment the image with thresholding. The color associated with each class is determined by the mean color of all pixels within the extents of a particular class. Finally, any unclassified pixels are assigned to the closest class with the fuzzy c-means technique. The fuzzy c-Means algorithm can be summarized as follows:

    o Build a histogram, one for each color component of the image.

    o For each histogram, successively apply the scale-space filter and build an interval tree of zero crossings in the second derivative at each scale. Analyze this scale-space ``fingerprint'' to determine which peaks or valleys in the histogram are most predominant.

    o The fingerprint defines intervals on the axis of the histogram. Each interval contains either a minima or a maxima in the original signal. If each color component lies within the maxima interval, that pixel is considered ``classified'' and is assigned an unique class number.

    o Any pixel that fails to be classified in the above thresholding pass is classified using the fuzzy c-Means technique. It is assigned to one of the classes discovered in the histogram analysis phase.
The fuzzy c-Means technique attempts to cluster a pixel by finding the local minima of the generalized within group sum of squared error objective function. A pixel is assigned to the closest class of which the fuzzy membership has a maximum value. For additional information see

    Young Won Lim, Sang Uk Lee, "On The Color Image Segmentation Algorithm Based on the Thresholding and the Fuzzy c-Means Techniques", Pattern Recognition, Volume 23, Number 9, pages 935-952, 1990.

USER PREFERENCES
Preferences affect the default behavior of display(1). The preferences are either true or false and are stored in your home directory as .displayrc:

display image centered on a backdrop
    This backdrop covers the entire workstation screen and is useful for hiding other X window activity while viewing the image. The color of the backdrop is specified as the background color. Refer to X RESOURCES for details.

confirm on program exit
    Ask for a confirmation before exiting the display(1) program.

correct image for display gamma
    If the image has a known gamma, the gamma is corrected to match that of the X server (see the X resource displayGamma).

apply Floyd/Steinberg error diffusion to image
    The basic strategy of dithering is to trade intensity resolution for spatial resolution by averaging the intensities of several neighboring pixels. Images which suffer from severe contouring when reducing colors can be improved with this preference.

use a shared colormap for colormapped X visuals
    This option only applies when the default X server visual is PseudoColor or GrayScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. Choose Private and the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.

display images as an X server pixmap
    Images are maintained as a XImage by default. Set this resource to True to utilize a server Pixmap instead. This option is useful if your image exceeds the dimensions of your server screen and you intend to pan the image. Panning is much faster with Pixmaps than with a XImage. Pixmaps are considered a precious resource, use them with discretion.

ENVIRONMENT

display
    To get the default host, display number, and screen.

SEE ALSO
animate(1), import(1), montage(1), mogrify(1), mosaic(1), convert(1), combine(1), xtp(1)

COPYRIGHT
Copyright (C) 2000 ImageMagick Studio, a non-profit organization dedicated to making software imaging solutions freely available. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files ("ImageMagick"), to deal in ImageMagick without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of ImageMagick, and to permit persons to whom the ImageMagick is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of ImageMagick. The software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall ImageMagick Studio be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with ImageMagick or the use or other dealings in ImageMagick. Except as contained in this notice, the name of the ImageMagick Studio shall not be used in advertising or otherwise to promote the sale, use or other dealings in ImageMagick without prior written authorization from the ImageMagick Studio.

ACKNOWLEDGEMENTS
The MIT X Consortium for making network transparent graphics a reality. Peder Langlo, Hewlett Packard, Norway, made hundreds of suggestions and bug reports. Without Peder, ImageMagick would not be nearly as useful as it is today. Rod Bogart and John W. Peterson, University of Utah. Image compositing is loosely based on rlecomp of the Utah Raster Toolkit. Michael Halle, Spatial Imaging Group at MIT, for the initial implementation of Alan Paeth's image rotation algorithm. David Pensak, E. I. du Pont de Nemours and Company, for providing a computing environment that made this program possible. Paul Raveling, USC Information Sciences Institute. The spatial subdivision color reduction algorithm is based on his Img software.

AUTHORS
John Cristy, ImageMagick Studio