TruePaint/Prism Paint file format

TruePaint       *.TPI
Prism Paint     *.PNT

  1 long        $504e5400 'PNT ' 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   Interleaved bitplanes for bits_per_pixel<16, a 16 bit 
                           word per pixel for 16-bit pictures, RRRRrGGGGGgBBBBBb.
                           The line length is a multiple of 16 pixels for all bit depths
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.

See also PackBits Compression Algorithm

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