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Manual Reference Pages  -  XGRABSC (1)


xgrabsc - grab rectangular screen images and store in files


General Options
Selection Options
Image Processing Options
Output Format Options
Postscript Options
Processing Order
See Also


   xgrabsc [-d display] [-id windowId] [-colorwin windowId] [-o outputFile] [-s seconds] [-post seconds] [-b percent] [-and andBits] [-or orBits] [-page widthxheight-hmarg-vmarg] [-bell -grab -verbose -borders -frame -key -stretch -root -click -coords widthxheight+x+y -offset widthxheight+x+y
-reverse -bw -mdither -dither -halftone
-ps -cps -simple -xwd -ppm -xwdxy -bm -bm2 -bm3 -puzzle
-bin -comp -eps -l -limit -preview -prev -previewonly -colproc


xgrabsc lets you grab arbitrary rectangular images from an X server and writes them to standard output in a variety of formats.

Command line options also allow reduction of colormaps, halftoning and dithering of color images, and direct mapping of color images to monochrome.

Options must be seperated with spaces or tabs. They may be preceded with a dash, but this optional and provided for Un*x addicts. Many may also be prefixed with ’no’, or an additional dash, to turn them off.

The default output format is gray-scale non-encapsulated Postscript, with image compression (if image compression significantly reduces the amount of output).

If you desire an output format not produced by xgrabsc, try using the PBM package by Jef Poskanzer to convert xgrabsc to that format. PBM can read xgrabsc’s PPM and XWD output formats and convert them to a lot of different formats.


-d displayName or -display displayName
  Use an alternate display. If no display is specified on the command line, xgrabsc looks for the environment variable DISPLAY for the name of the display and screen to grab from. Note that you must have permission to access the display on another computer.
-bell The display’s bell is normally rung while the screen is being accessed. This turns the bell on or off (-nobell will turn it off).
-grab Enable server grabs. Normally xgrabsc will "grab" the server so that the screen is frozen while a rectangle is selected and the image is extracted. If the screen is not frozen, rubber-banding may cause video droppings on portions of the screen that are changing. Use -nograb to turn off server grabs.
Server grabs are automatically disabled if verbose output is requested to avoid freezing up the system.
-o output-file or -output output-file
  Write output to output-file instead of standard output. The output-file name, minus directory and extension, is used as the internal name for the image in formats supporting image names. Postscript, xwd, pixmap and bitmap formats all support image names.
-s seconds or -sleep seconds
  Sleep for seconds seconds before commencing operation. This should be used if you need some time to get the target image ready.
-post seconds
  Sleep for seconds seconds after window/rectangle selection. This is commonly used to pop up menus after a window has been selected but before xgrabsc takes its snapshot.
-verbose Display processing information on standard error output (stderr).


-id window ID
  Dump the window with the given ID. ID numbers can be in decimal, or hexidecimal (prefixed with "0x"). The name of a window can be given instead of an ID number, and xgrabsc will look for the first window with that name.
-key Select the window under the mouse when the Control key is pressed. This option is normally used in getting images of menus. Pop up the menu, optionally move the pointer to the window containing the menu, and strike the Control key to begin the dump.
-root Dump the entire screen (root window).
-stretch Use rubber-band rectangle to select region to grab. This is the default.
-click Wait for a click on a window and dump the selected window.
-coords widthxheight+x+y
  Selects the given area of the screen, without mouse or keyboard interaction. Use this if you need to grab the same area of the screen over and over again. Standard X coordinate notation can be used, but a width and height must be given.
-coords widthxheight+x+y
  Offsets the area to be grabbed by x@y and changes the area’s width and height to widthxheight. Using this you can grab a sub-area of the source area, or even grab an area adjacent to the source area.


-nobdrs or -noborders
  Remove window borders from window images. This option applies only to selection by ID (-id) or xwd-style selection (-click).
Note that Motif-style window frames are not window borders. To remove these you should use the -noframe option. The xgrab window interface’s Include Borders option removes both frames and borders.
-bdrs or -borders
  Include window-manager borders in window images. This option applies only to selection by ID (-id) or xwd-style selection (-click). Use -nobdrs or -noborders to turn it off.
-b percent or -brighten percent
  brighten or darken the image by percent. Percentages are given as integers. 100 is the base and a larger number will brighten the image while a smaller number will darken the image.
-and andBits
  Clear all colormap bits up to the given plane. This has the effect of darkening the image somewhat and shrinking the apparent depth of the image (and, consequently, the size of the color table). AndBits should be in the range [1-8] inclusive.
-or orBits
  Set all colormap bits up to the given plane. This brightens the image somewhat and also shrinks the apparent depth of the image. When both -A and -O are specified, ANDing will occur before ORing.
-reverse Reverse the colors in the image. The bits of each color used in the image are inverted.
-bw Convert the source color image to a monochrome bitmap. All colors falling below the average color intensity are mapped to black. Others are mapped to white.
  Convert the source color image to a halftoned monchrome bitmap. Resolution is maintained by increasing the size of the image by a factor of four on both axes.
-mdither Convert the source color image to a dithered monochrome bitmap. This is like halftoning, but resolution is sacrificed to keep the resulting image the same size as the original. The matrix dithering algorithm used with this option is most suitable for line-drawings and text. For more complex graphics the -dither option is recommended.
-dither Convert the source color image to a dithered monochrome bitmap with the Floyd-Steinberg algorithm.
  Turns off any dithering. Use this if your XGRABSC environment variable specifies dithering and you want to override it to produce an undithered image.
-colorWin windowId
  Specifies a window id (in hex) whose colormap should be used for the grabbed image. Generally xgrabsc will find the correct colormap for your image. If you have lots of private colormaps around you may need to use this option to ensure that xgrabsc selects the proper one.
ID numbers can be in decimal, or hexidecimal (prefixed with "0x"). The name of a window can be given instead of an ID number, and xgrabsc will look for the first window with that name.


-cps Write output in Postscript format using the colorimage operator for color printers. Color to grayscale conversion is bundled into the output so you can actually use either color or cheaper grayscale printers. For monochrome displays, the -ps option will give more compact output.
-ps Write output in Postscript format for greyscale printers. The number of bits per Postscript sample is determined by the depth of the image.
-ppm Write output in Portable Bitmap format. Unix image viewers such as xv and ImageMagick can accept this format, and the Portable Bitmap package can convert this to many other image formats.
-xwd Write output in xwd format. Use this if you want to convert to another output format with Pbm+.
Write output in \FIxwd -xy format. This is like xwd, but allows black and
  white images to be written with eight pixels per byte instead of the default one pixel per byte. While xwud and xpr will handle this format, some programs will not.
-bm Write the output in X Bitmap format if the image is black and white, or X Pixmap format if the image is gray or color.
-bm2 Write the output in X Bitmap format if the image is black and white, or X Pixmap format 2 if the image is gray or color. -bm3 Write the output in X Bitmap format if the image is black and white, or X Pixmap format 3 if the image is gray or color.
-puzzle Write output in a format suitable for loading into the puzzle program (see example below).


  Enable or suppress Postscript image run-length encoding. Postscript output is normally compressed to minimize the size of output. If your printer can’t handle compressed output, you should use -nocompress to turn off compression.
-eps Create Encapsulated Postscript output, rather than normal stand-alone Postscript. This adds EPSF header comments and removes all scaling and translation of the image.
-l or -landscape
  Use landscape layout (with page width and height exchanged) for Postscript output. This option is ignored if Encapsulated Postscript output is requested. Width and height may be specified with the -page option.
-bin Write Postscript output in binary rather than using hexidecimal encoding. This causes the image portion of the output to use half as much space, decreasing transmission time to the printer. Note that not all print spoolers can handle 8 bit binary data, so this may not work on your system!
-limit For Postscript output, check printer memory availability before attempting to print an image (the code to perform the checks is integrated into the output of xgrabsc). This is turned off if Encapsulated Postscript output is requested, and may be disabled completely when building the xgrabsc program. On the command line it may be turned off with -nolimit.
-preview or -prev
  Selects Encapsulated Postscript output with an EPSI preview image in its header. The preview image, if necessary, is dithered to black and white either with a default dithering algorithm or one you specify on the command line (e.g., -mdither). Programs such as Frame use preview images to display the postscript image during editing sessions. If you don’t have a preview image, Frame will display a blank rectangle. The image will print OK but you won’t see it while editing.
  Like -preview but writes only the preview portion, not the postscript image. This may be used to add the preview to an existing EPS file after having displayed it using a PostScript interpreter.
-page widthxheight-marginWidth-marginHeight
  Sets the size of the paper and the borders you desire around the edge of the paper. Xgrabsc will reduce the image if necessary to keep it within the borders you specify. The default page size and margins are set when xgrabsc is built. Measurements are in inches (e.g., 8.5x11.0-0.5-0.5)


It is helpful to know the order of processing when multiple processing options are given on the command line.

Processing is done in five phases: 1) set up, 2) obtain image, 3) process colors, 4) poly->monochrome conversions, and 5) output conversion.

The set-up phase includes processing command-line options, sleeping, connecting to X-Windows, freezing the screen, and grabbing the mouse if necessary.

If the mouse is grabbed for rubber-banding, an upper-left-corner cursor is displayed until the left mouse button is pressed. A lower-left-corner cursor is then displayed while drawing rubber-rectangles until the mouse button is released.

If the mouse is grabbed for xwd-style window selection, an xwd-style cursor is displayed until the left mouse button is pressed.

The mouse is then released.

The bell is then run and the image is pulled from the screen.

Following the image-grab, the bell is run twice and the screen is released.

If the image is not monochrome, the color manipulation functions are then applied in this order: brighten, AND, and OR, reverse.

Only one polychrome to monochrome conversion is allowed. If none of these is chosen, the color table of a polychrome image is compressed in preparation for output conversion.

The output stream is then opened and the image is written in the selected output format.


XGRABSC - specifies command line arguments to be processed before those actually entered on the command line.

DISPLAY - specifies the name of the display that xgrabsc should grab from.


The simplest form of use, giving Postscript output, is

   xgrabsc >

To write output in Postscript format and send to the printer, use

   xgrabsc | lpr

It is sometimes helpful to brighten an image somewhat before it is formatted for Postscript output. E.g., to brighten by 30%

   xgrabsc -b 130 | lpr

If your printer supports color, and your display is color, you can have xgrabsc generate color output instead of gray scale:

   xgrabsc -cps | lpr

The default Postscript output attempts to scale the image so that it will all fit on one page, and is centered on the page. If you are grabbing images to include in documents, such as with FrameMaker, you should ask for Encapsulated Postscript output with the -eps switch. For example:

    xgrabsc -eps -o image1.eps

To select an entire window, write output in puzzle format and read into the puzzle program, use the commands

   xgrabsc -click -puzzle >outfile.pzl    
puzzle -picture outfile.pzl

To have xgrabsc sleep for three seconds before rubber-banding, display processing information, and have the result displayed with xwud,

   xgrabsc -xwd -verbose -s 3 | xwud

To grab an image from another server and then reduce the colormap to three bits by ANDing, use

   xgrabsc -d other:0.0 -and 5 -bm >outfile.xpm

You will, of course, have to go to the other machine to select the image with that machine’s mouse.

If you know the name or ID number of the window you want to snapshot you can direct xgrabsc to that window on the command line. Utilities like xlswins or xwininfo can be used to find the names and ID numbers of windows.

To grab an mpegplay image and display it in xwud, use    xgrabsc -xwd -id "MPEG Play" | xwud

You can also specify a sub-region to grab, as in    xgrabsc -xwd -id "MPEG Play" -offset 100x100+10+10 | xwud

Grabbing an area with the /fI-coords/fP option will use the root window’s colormap unless you specify an alternate window to use for color processing. If your display allows more than one colormap to be installed at once and you are displaying an mpeg video that uses a private colormap, your output using the /fI-coords/fP command would be technicolor without a /fI-colorwin/fP option specifying the mpeg window. E.g.,    xgrabsc -xwd -coords 300x300+10+10 -colorwin "MPEG Play" | xwud


Colormaps larger than 256 entries are not currently supported. This means that it won’t work with your fancy 24-bit display.

The default screen visual is used as the visual for the image. Visuals are associated with particular windows, and xgrabsc pretends ignorance about any windows but the root.

This software has been tested with StaticGray and 8-plane PseudoColor on DECStations (using both UWS 2.2 and X11 Release 4). It has also been tested with 8-plane PseudoColor on Sun SparcStations and various other platforms using X11 Release 4 and Release 5.

X11 Pixmap format is rather verbose. You may want to run large images through the compress utility before storing them in a file. E.g.,

   xgrabsc -bm | compress >outfile.xpm.Z


     Bruce Schuchardt
    GemStone Systems, Inc.


Some of the source code for xgrabsc came from the xloadimage project by Jim Frost ( and others. Jim’s copyright has been included both here and in the source code.

The idea for using run-length encoding for Postscript output came from the xwd2ps project by Robert Tatar and Craig A. McGowan.

The ad2c.sed script that makes it possible to let you run xgrab without installing everywhere is part of the ad2c package developed by George Ferguson.


Yves Arrouye wrote the EPS Preview and page-configuration enhancements.


Copyright (c) 1990-93 Bruce Schuchardt

Xgrabsc 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 cpyright.h 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.



X(1X), xhost(1), xwd(1X), xwud(1X), xwd2ps(1X), xloadimage(1X), xpm(1X), xpr(1X), puzzle(1X), compress(1), uncompress(1), xv(1X)
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