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 XSHOWGIF(1)                                                     XSHOWGIF(1)
                                27 April 1990

      xshowgif - load gif images into an X11 window

      xshowgif [global_options] {[image_options] image ...}

      Xshowgif displays gif images in a X11 window.

      Xshowgif is a pared down version of Jim Frost's (
      xloadimage program.  Unlike xloadimage this program only displays GIF
      files in a X11 Window.  Support for alternate image types and loading
      images into the root window have been removed.  These features were
      removed so the program could support some additional GIF file features
      that cannot be supported in conjunction with these other features such
      as display of multiple GIF images in a file.

      If an image is larger then the window, you may move the image around
      in the window by dragging with the left mouse button.  The cursor will
      indicate which directions you may drag, if any.  You may exit the
      window by typing 'q', 'Q' or '^C' when the keyboard focus is on the
      window.  If more then one image is specified on the command line, 'N'
      moves you to the next gif file, while 'P' moves you to the previous
      gif file.  If the gif file contains more then one image 'n' moves you
      to the next image in the gif file.  If there are no more images in the
      file, 'n' moves to the next file on the command line.

      If the destination display cannot support the number of colors in the
      image, the image will be dithered (monochrome destination) or have its
      colormap reduced (color destination) as appropriate.  This can also be
      done forcibly with the -halftone and -colors options.

      A variety of image manipulations can be specified, including
      brightening, clipping, dithering, depth-reduction, and zooming.  Most
      of these manipulations have simple implementations; speed was opted
      for above accuracy.

      A wide variety of common image manipulations can be done by mixing and
      matching the available options.  See the section entitled HINTS FOR
      GOOD IMAGE DISPLAYS for some ideas.

      The following options affect the global operation of xshowgif.  They
      may be specified anywhere on the command line.

      -border color
              This sets the background portion of the window which is not
              covered by any images to be color.

      -display display_name
              X11 display name to send the image(s) to.

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 XSHOWGIF(1)                                                     XSHOWGIF(1)
                                27 April 1990

      -geometry WxH[{+-X}{+-}Y]
              This sets the size of the window onto which the images are
              loaded to a different value than the size of the image.  This
              can be used to reduce the size of the destination window.

      -help   Displays a short summary of xshowgif command line syntax.

      -quiet  Forces xshowgif to be quiet.  Normally xshowgif will display
              the image size and colormap depth.

              Causes xshowgif to be talkative, telling you and any special
              processing that it has to do.

              Print the version number and patchlevel of this version of

      The following options may preceed each image.  These options are local
      to the image they preceed.

      -background color
           Use color as the background color instead of the default (usually
           white but this depends on the image type) if you are transferring
           a monochrome image to a color display.

      -brighten percentage
           Specify a percentage multiplier for a color image's colormap.  A
           value of more than 100 will brighten an image, one of less than
           100 will darken it.

      -colors n
           Specify the maximum number of colors to use in the image.  This
           is a way to forcibly reduce the depth of an image.

      -clip X,Y,W,H
           Clip the image before loading it.  X and Y define the upper-left
           corner of the clip area, and W and H define the extents of the
           area.  A zero value for W or H will be interpreted as the
           remainder of the image.

           Dither a color image to monochrome.  This algorithm is very
           trivial; the -halftone option may look better if you don't mind
           the blown-up image.

      -foreground color
           Use color as the foreground color instead of black if you are
           transferring a monochrome image to a color display.  This can
           also be used to invert the foreground and background colors of a
           monochrome image.

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 XSHOWGIF(1)                                                     XSHOWGIF(1)
                                27 April 1990

           Force halftone dithering of a color image when displaying on a
           monochrome display.  This happens by default when viewing color
           images on a monochrome display.  This option is ignored on
           monochrome images.  This dithering algorithm blows an image up by
           sixteen times; if you don't like this, the -dither option will
           not blow the image up (but won't look as nice).

      -name image_name
           Force the next argument to be treated as an image name.  This is
           useful if the name of the image is -dither, for instance.

      -xzoom percentage
           Zoom the X axis of an image by percentage.  A number greater than
           100 will expand the image, one smaller will compress it.  A zero
           value will be ignored.

      -yzoom percentage
           Zoom the Y axis of an image by percentage.  See -xzoom for more

      -zoom percentage
           Zoom both the X and Y axes by percentage.  See -xzoom for more
           information.  Technically the percentage actually zoomed is the
           square of the number supplied since the zoom is to both axes, but
           I opted for consistency instead of accuracy.

      To double the size of an image:

           xshowgif -zoom 200 my.gif

      To halve the size of an image:

           xshowgif -zoom 50 my.gif

      To brighten a dark image:

           xshowgif -brighten 150 my.gif

      To darken a bright image:

           xshowgif -brighten 50 my.gif

      Since images are likely to come from a variety of sources, they may be
      in a variety of aspect ratios which may not be supported by your
      display.  The -xzoom and -yzoom options can be used to change the
      aspect ratio of an image before display.  If you use these options, it
      is recommended that you increase the size of one of the dimensions
      instead of shrinking the other, since shrinking looses detail.  For

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 XSHOWGIF(1)                                                     XSHOWGIF(1)
                                27 April 1990

      instance, many GIF images have an X:Y ratio of about 2:1.  You can
      correct this for viewing on a 1:1 display with either -xzoom 50 or
      -yzoom 200 (reduce X axis to 50% of its size and expand Y axis to 200%
      of its size, respectively) but the latter should be used so no detail
      is lost in the conversion.

      One common complaint is that xshowgif does not have a -reverse
      function for inverting monochrome images.  In fact, this function is a
      special-case of the foreground and background coloring options.  To
      invert an image with a black foreground and white background (which is
      standard), use -foreground white -background black.  This will work on
      both color and monochrome displays.

      Modifications to xloadimage by
      Richard J. Greco
      Intel Scientific Computers

      Xloadimage was written by
      Jim Frost
      Saber Software

      Other contributing people include Barry Shein (, Kirk
      Johnson (, Mark Snitily (zok!, W.
      David Higgins (, and Dave Nelson

      Copyright (c) 1989, 1990 Jim Frost and others.

      Xshowgif is a derivitive work of xloadimage by Jim Frost et. al. and
      is subject to all copyright restrictions of xloadimage.

      Xloadimage is copywritten material with a very loose copyright
      allowing unlimited modification and distribution if the copyright
      notices are left intact.  Various portions are copywritten by various
      people, but all use a modification of the MIT copyright notice.
      Please check the source for complete copyright information.  The
      intent is to keep the source free, not to stifle its distribution, so
      please write to me if you have any questions.

      Zooming dithered images, especially downwards, is UGLY.

      The dithering algorithm used by -dither could be better, and both
      -dither and -halftone assume that a color's brightness is the sum of
      its RGB values, which is not correct but has the advantage of being
      simple and fast.

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 XSHOWGIF(1)                                                     XSHOWGIF(1)
                                27 April 1990

      Images can come in a variety of aspect ratios.  Xshowgif cannot detect
      what aspect ratio the particular image being loaded has, nor the
      aspect ratio of the destination display, so images with differing
      aspect ratios from the destination display will appear distorted.  See
      HINTS FOR GOOD IMAGE DISPLAYS for more information.

      Only PseudoColor, GrayScale, StaticColor, and StaticGray visuals are
      supported.  These are the most common visuals so this isn't usually a

      Some window managers do not correctly handle window size requests.  In
      particular, many versions of the twm window manager use the MaxSize
      hint instead of the PSize hint, causing images which are larger than
      the screen to display in a window larger than the screen, something
      which is normally avoided.  Some versions of twm also ignore the
      MaxSize argument's real function, to limit the maximum size of the
      window, and allow the window to be resized larger than the image.  If
      this happens, xshowgif merely places the image in the upper-left
      corner of the window and uses the zero-value'ed pixel for any space
      which is not covered by the image.  This behavior is less-than-
      graceful but so are window managers which are cruel enough to ignore
      such details.

      The order in which operations are performed on an image is independent
      of the order in which they were specified on the command line.
      Wherever possible I tried to order operations in such a way as to look
      the best possible (zooming before dithering, for instance) or to
      increase speed (zooming downward before compressing, for instance).

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