handiklap
04-12-2006, 08:37 PM
Does anyone know of an online math breakdown of compositing modes? i.e. to composite in screen mode, evaluate this expression for pixel A and pixel B, to composite in overlay mode, evaluate this expression, etc. etc. I'm trying to script a custom compositing utility and this is pretty much the foundation for it all. I've found a bit of information with google, but sometimes it seems a bit vague. I understand that for the most part, compositing uses the value components of pixels for comparison, but what I get lost on is how, for example, a multiply mode - which is usually described as multiplying the value of corresponding pixels - is actually evaluated. Am I wrong in assuming the pixel value is on a 256-level grey scale? I'd like to find some useful info on screen, overlay, and multiply in particular, but any others would be great if anyone could link/explain.
tia
Edit: ok nm the first part, found this (http://partners.adobe.com/public/developer/en/pdf/blend_modes.pdf), and it would suggest that the value is rather a decimal value between 0 and 1, inclusive. Is that correct? I'm guessing that from the fact that with Multiply, any value multiplied with black will result in black, and any value multiplied with white remains unchanged.
tia
Edit: ok nm the first part, found this (http://partners.adobe.com/public/developer/en/pdf/blend_modes.pdf), and it would suggest that the value is rather a decimal value between 0 and 1, inclusive. Is that correct? I'm guessing that from the fact that with Multiply, any value multiplied with black will result in black, and any value multiplied with white remains unchanged.