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154 lines
4.1 KiB
HTML
154 lines
4.1 KiB
HTML
<!doctype HTML public "-//W3O//DTD W3 HTML 2.0//EN">
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<HTML>
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<HEAD>
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<TITLE>gif2herc</TITLE>
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<link rev=made href=mailto:esr@snark.thyrsus.com>
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</HEAD>
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<BODY>
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Go to <a href="index.html">index page</a>.
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<CENTER><H1>gif2herc</H1></CENTER>
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A program to display images saved as GIF files on an IBM PC Hercules
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graphic card. The program operates as follows:<P>
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<OL>
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<LI>
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Read GIF file header and determine size of the image.<P>
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<LI>
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Dynamically allocate enough memory to hold all the image internally.
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One byte per pixel is always allocated, so a little bit more than
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width*height (of screen, not image) bytes are required.<P>
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<LI>
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Reads the image in. Interlaced images are read correctly, although
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they are displayed sequentially.<P>
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<LI>
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Display first image using the defaults as set by the command line option.<P>
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<LI>
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Goes to interactive mode. For full description of the interactive mode
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see below.<P>
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</OL>
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<H1>Usage:</H1>
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<pre>
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gif2herc [-q] [-d dither] [-z zoom] [-t bw] [-m map] [-i] [-b] [-h] gif-file
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</pre>
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If no gif-file is given, gif2herc will try to read a GIF file from stdin.<P>
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<H1>Memory required:</H1>
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Screen.
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<H1>Options:</H1>
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<DT> [-q]
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<DD> Quiet mode. Defaults off on MSDOS, on under UNIX. Controls printout
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of running scan lines. Use -q- to invert.<P>
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<DT> [-d dither]
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<DD> Sets size of dithering matrix, where dither can be
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2,3 or 4 only (for 2x2, 3x3 and 4x4 dithering matrices). Default is 2.
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Note: the image will be dithered only if the mapping (see -m)
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selected dithering mode.<P>
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<DT> [-z zoom]
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<DD> Sets zoom factor of the image. Zoom factor should be
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power of 2 up to 256. Default is 1 (no zoom).<P>
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<DT> [-t bw]
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<DD> Sets threshold level for B&W mapping in percent.
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This threshold level is used in the different mappings as selected via -m.
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Default is 19%.<P>
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<DT> [-m map]
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<DD> Select method to map colors to B&W. Mapping can be:
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<DL>
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<DT>0<DD>
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Every non-background color is considered foreground (white).
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<DT>1<DD>
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0.3 * RED + 0.59 * GREEN + 0.11 * YELLOW > BWThreshold is considered white.
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<DT>2<DD>
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Colors are mapped as in 1, and use dithering of size as defined using
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-d option. BWthreshold is used here as scaler.
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</DL>
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Default is option 0, which is much faster than the other two.<P>
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<DT> [-i]
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<DD> Invert the image, i.e. black -> white, white -> black.<P>
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<DT> [-b]
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<DD> Disable beeps. Every time the image is complete, or a wrong key was
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presses, sound is generated. The -b option disables that.<P>
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<DT> [-h]
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<DD> Print one line of command line help, similar to Usage above.<P>
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</DL>
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<H1>Interactive mode:</H1>
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Once the image is displayed, the program goes into an interactive mode
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which recognizes the following commands:
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<DL>
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<DT> C - get Color and position
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<DD> In this submenu, a cursor appears and the location and color of the
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pixel underneath it are printed. The 4 arrows may be used (shifted for
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faster movement) to move the cursor. Any other key will abort this
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submode.<P>
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<DT> D - zoom Down
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<DD> Zoom down by factor of 2 unless current zoom factor is 1.<P>
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<DT>H - Increase dither matrix size
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<DD>...unless current size is maximum (4), in which case size is set
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to minimum (2).<P>
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<DT>I - Invert
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<DD>Invert the image, i.e. white -> black, black -> white.<P>
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<DT>M - Method
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<DD>Increment color -> BW mapping method, unless current method is maximum
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(2), in which case method is set to minimum (0).<P>
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<DT> R - Redraw
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<DD> Redraw the image.<P>
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<DT> S - print Status
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<DD> Print status of image and program.<P>
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<DT> U - zoom Up
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<DD> Zoom up by factor of 2 unless current zoom factor is 256.<P>
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<DT> arrow keys
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<DD> The 4 arrow keys can be used to pan in the desired direction, if the image
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overflows in that direction. If the image fits into the screen, arrow
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keys are ignored. The panning steps are 1/2 screen if not on image end.<P>
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<DT> SPC - abort
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<DD> Space bar may be used to abort current image drawing.<P>
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<DT> ESC - abort
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<DD> Escape may be used to abort current image drawing.<P>
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</DL>
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<H1>Author:</H1>
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Gershon Elber
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<HR>
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<ADDRESS>Eric S. Raymond <A HREF="mailto:esr@thyrsus.com"><esr@snark.thyrsus.com></A></ADDRESS>
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</BODY>
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</HTML>
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