Andrew Coppin wrote:
I just uploaded a new version of the AC-Colour package...
Thanks for this. Your algorithm for scaling brightness is not correct however. The RGB values in all popular image formats are not linear. They use a gamma transfer function. So your algorithm will indeed change the colors in an image, not just its brightness. In some cases the change in color can be quite drastic. For a long-winded explanation and many examples, see: http://www.4p8.com/eric.brasseur/gamma.html You may want to implement one of the popular gamma transfer functions, such as BT.709 or sRGB. The former may also be useful for your AC-PPM package, since the PPM image format uses it, as specified in its documentation: http://netpbm.sourceforge.net/doc/ppm.html sRGB is used in most other popular image formats on the web nowadays.
Colour maps. Give it some control points, and it'll (linearly) interpolate between them
Your algorithm for this is actually not linear at all, since RGB values are generally not linear, as above. Regards, Yitz