fe6c45e36e
previous fix for 2D image painting were done, and also: * For brushes that do masking (keeping the max contribution to a pixel limited), the alpha from textures is now part of the mask. In many cases the logic worked out the same and where it didn't it used to cause artifacts. * Color interpolation for smear and soften tools now happens in premultipied space, to avoid bleeding of RGB colors from zero alpha areas. * Fix a few cases where byte <=> float conversion was not doing the proper straight <=> premul conversion. * Replace some float division by constants with multiplications, is faster. Note: float texture painting seems to have some issues updating the OpenGL texture, but issue was already there before this commit.