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Next: Scale and Bias Up: 13.2.4 The Color Matrix Previous: 13.2.4 The Color Matrix   Contents Equivalent Functionality Without SGI_color_matrix

Unfortunately, the functionality of SGI_color_matrix is difficult to efficiently duplicate on systems which do not support the extension. In the case where the image is going from the host to the framebuffer (a glDrawPixels() operation), the best way to handle the situation is the split the image up into red, green, blue, and alpha images (via application processing or a draw followed by reads with format set to GL_ RED, GL_ GREEN, GL_ BLUE, or GL_ ALPHA). The red, green, blue, and alpha images can be drawn as GL_ LUMINANCE images. RGBA scale operations are applied, with the four values equal to the row of the matrix corresponding to source channel. The images are composited in the framebuffer using blending (glBlendFuncGL_ ONE, GL_ ONE(GL_ ONE, GL_ ONE)).