Fast GPU color transforms with XNA
Filed under: XNA
Some time ago I came across a nice Siggraph paper on Using Lookup Tables to Accelerate Color Transformations and since then have been interested in seeing it at work.
The basic premise is that a 3d texture is used as a lookup table where the input 3d coords represent the input colour. A nice and simple fragment shader is then used to access this lookup texture and return the transformed color. Any number of any complexity operations can be stored in the lookup texture as long as you’re mapping the single input pixel (that is, no neighbours). Gamma correction, contrast, saturation, colorisation, levels, colour keying etc, are all possible in any combination at a fixed small cost.
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