The PCX files are created by the programs of the ZSoft Paintbrush family and the FRIEZE package by the same manufacturer. A PCX file contains only one image, the data for this image and possibly palette information for this image. The encoding scheme used for PCX encoding is a simple RLE mechanism, see ALGRTHMS.txt for further information. A PCX image is stored from the upper scan line to the lower scan line. The size of a decoded scan line is always an even number, thus one additional byte should always be allocated for the decoding buffer. The header has a fixed size of 128 bytes and looks like this : OFFSET Count TYPE Description 0000h 1 byte Manufacturer. 10=ZSoft 0001h 1 byte Version information 0=PC Paintbrush v2.5 2=PC Paintbrush v2.8 w palette information 3=PC Paintbrush v2.8 w/o palette information 4=PC Paintbrush/Windows 5=PC Paintbrush v3.0+ 0002h 1 byte Encoding scheme, 1 = RLE, none other known 0003h 1 byte Bits per pixel 0004h 1 word left margin of image 0006h 1 word upper margin of image 0008h 1 word right margin of image 000Ah 1 word lower margin of image 000Ch 1 word Horizontal DPI resolution 000Eh 1 word Vertical DPI resolution 0010h 48 byte Color palette setting for 16-color images 16 RGB triplets 0040h 1 byte reserved 0041h 1 byte Number of color planes ="NCP" 0042h 1 word Number of bytes per scanline (always even, use instead of right margin-left margin). ="NBS" 0044h 1 word Palette information 1=color/bw palette 2=grayscale image 0046h 1 word Horizontal screen size 0048h 1 word Vertical screen size 004Ah 54 byte reserved, set to 0 The space needed to decode a single scan line is "NCP"*"NBS" bytes, the last byte may be a junk byte which is not displayed. After the image data, if the version number is 5 (or greater?) there possibly is a VGA color palette. The color ranges from 0 to 255, 0 is zero intensity, 255 is full intensity. The palette has the following format : OFFSET Count TYPE Description 0000h 1 byte VGA palette ID (=0Ch) 0001h 768 byte RGB triplets with palette information EXTENSION:PCX OCCURENCES:PC PROGRAMS:PC Paintbrush SEE ALSO:
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