libgd patch for alpha-channel mixing

This is a patch to add nicer alpha-channel mixing to the GD module. It introduces two new PHP functions: ImageLayerEffect() & ImageColorMatch() ImageLayerEffect() is similar to the existing ImageAlphaBlending() function in that it affects the way pixel drawing will be done during any kind of drawing function. It extends the functionality by allowing you to use new effect modes. There are four modes: replace, alpha, normal and overlay. Replace and alpha are like ImageAlphaBlending(FALSE) and ImageAlphaBlending(TRUE) respectively. "Normal" mode is like alpha but works on transparent and semi-transparent backgrounds. "Overlay" is like the overlay layer effect in graphics programs. The ImagePSText() function can now draw on arbitrary backgrounds using the normal layer effect (my technique is to use a text background colour that has the same RGB as the text foreground but a transparent alpha.) ImageColorMatch() is a function I've been using to tweak the ImageTrueColorToPalette() results. I find that the generated palette gets close, but doesn't quite match sometimes. This function fixes that "problem" (at least it works for me). Any thoughts? Should I go ahead and commit this? I've never committed to PHP before so go easy on me :-). I've been using essentially the same code on a PHP-4.1.0 installation for a while now and I believe it works OK. Tim

Attachment: [text/x-diff] php-4.3.0ttoohey-0.1.diff