TruePaint/Prism Paint file format
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TruePaint *.TPI
Prism Paint *.PNT
1 long $504e5400 'PNT\0' TruePaint Magic
1 word $0100 ???? file version
1 word palette_size Might be there in true color
1 word x_size
1 word y_size
1 word bits_per_pixel
1 word compression, $0000 uncompressed, $0001 packbits compressed
1 long picture_data_size = ((x_size+15)&0xffff0)*y_size*bits_per_pixel/8
(uncompressed)
108 bytes $0
---------
128 bytes total for header
3*palette_size words Palette data, RGB, values 0..1000. The colors are in VDI order
picture_data_size bytes The line length is a multiple of 16 pixels for all bit depths
Interleaved bitplanes for bits_per_pixel<16
16 bit word per pixel for 16-bit pictures, RRRRrGGGGGgBBBBBb
24 bit is stored R, G, B in that order
The prism paint compressed format uses the Packbits compression algorithm. For every
scanline the bitplanes are compressed separately. The falcon high-color resolution
(16 bit) is compressed as if there were 16 bitplanes, which there are not.
The same rule applies to 24 bits per pixel.
Additional information:
The TruePaint manual describes the format as designed for high speed and only writes
uncompressed files. Prism Paint on the other hand offers compression every time a
file is saved with an alert box (yes/no).
See also PackBits Compression Algorithm
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