Large # of colors
A proposal for interchange format (IFF) for files with large number of
colors:
If the number of bit planes in an IFF file is greater than or equal to
twelve (12) and is divisable (withoug remainder) by 3 (e.g. 12, 15, 18, 21,
24), and there is no colormap chunk, then the colors shall be established
as follows:
1. Absolute color values will be used.
2. An equal number of bit planes will be allocated to each color
3. The bit planes will be allocated to Red, then Green, then Blue; with the
first (n/3) planes allocated to Red (i.e. planes 0..(n/3-1)).
4. The values shall be the same as if a monochrome picture (in the appropriate
color) were being rendered in a RastPort of n/3 bit-planes.
As an implementation detail for programs dealing with these files,
note that (in principal) ReadPixel() and WritePixel() can deal with 8-bit
values.
If you make four (4) RastPorts (one for the entire picture, and one each
for each 'color' (R,G,B), then color values can be directly written to the
small rast ports and WriteIFF() can handle the big one). Only a small
modification is neccessary to the current IFF read/write routines to allow
these large (deep) pictures (it is a define in the version I have denoting
the maximum number of bit-planes).
If you are currently generating such pictures and cannot conform to this,
please contact me. I will be back in the country on 30 Sep.