83 lines
3.5 KiB
Plaintext
83 lines
3.5 KiB
Plaintext
Gif2Herc
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--------
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Program to display images saved as GIF files on IBM PC Hercules graphic card.
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The program has few stages as follows:
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1. Reads GIF file header and determines size of it.
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2. 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.
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3. Reads all the image in. Interlaced images are read correctly in, although
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they are displayed sequentially.
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4. Display first image using the defaults as set by the command line option.
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5. Goes to interactive mode. For full description of the interactive mode
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see below
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Usage:
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------
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Gif2Herc [-q] [-d DitherSize] [-z ZoomFactor] [-t BWThreshold] [-m Mapping]
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[-i] [-b] [-h] GifFile
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If no GifFile is given, Gif2Herc will try to read stdin for GIF file.
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Memory required:
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----------------
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Screen.
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Options:
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--------
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1. [-q] : quite mode. Default off on MSDOS, on on unix. Controls printout
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of running scan lines. Use -q- to turn off.
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2. [-d DitherSize] : Sets size of dithering matrix, where DitherSize 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 image will be displayed in this mode only if Mapping (see -m)
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selected this mode.
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3. [-z ZoomFactor] : 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).
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4. [-t BWThreshold] : 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%.
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5. [-m mapping] : Select method to map colors to B&W. Mapping can be:
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0 : Every none background color is considered foreground (white).
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1 : 0.3 * RED + 0.59 * GREEN + 0.11 * YELLOW > BWThreshold is considered
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white.
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2 : 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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Default is option 0 which is much faster than the other two.
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6. [-i] : Invert the image, i.e. black -> white, white -> black.
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7. [-b] : Disable beeps. Every time image is complete, or wrong key was
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presses, sound is generated. -b disables that.
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8. [-h] : print one command line help, similar to Usage above.
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Interactive mode:
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-----------------
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Once the image is displayed, the program goes into interactive mode
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which recognizes the following commands:
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1. C - get Color and Position.
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In this sub menu, a cursor appears, and the Color of the pixel the cursor
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is on, with its position in GIF file screen are printed. The 4 arrows may
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be used (shifted for faster movement) to move the cursor. Any other key will
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abort this sub mode.
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2. D - Zoom Down by factor of 2 unless current zoom factor is 1.
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3. H - Increase dither matrix size, unless current size is maximum (4), were
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size is set to minimum (2).
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4. I - Invert the image, i.e. white -> black, black -> white.
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5. M - increase Color -> BW mapping method, unless current method is maximum
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(2), were method is set to minimum (0).
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6. R - Redraw the image.
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7. S - print Status of image and program.
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8. U - Zoom Up by factor of 2 unless current zoom factor is 256.
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9. 4 arrow keys can be used to pan to the desire direction, if the image
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overflow to that direction. If, on the other hand, the image fit into the
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Hercules device, arrow keys are ignored. The panning steps are 1/2 screen if
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not on image end.
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9. ' ' - Space bar may be used to abort current image drawing.
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10. ESC - Escape key may be used to abort the program.
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