WME: Sprite background is not fully transparent if AlphaColor is set
|somaen, lolbot-iichan, tobiatesan
Discovered this issue at FoxTail game, that is using dinamic lighting on PNG sprites with transparent background.
I have exctacted sprite lighting source code and made a simple test game to demonstrate this issue without running FoxTail which is not fully supported by ScummVM yet: https://github.com/tobiatesan/wme_testsuite/tree/master/light_test/packages
Screenshots are attached. Resulting colot difference is not big (like #FFDED5 vs #FFDAD5), however you could see and feel this rectangle moving around character sprite both in test game and FoxTail.
Tested on latest ScummVM from dev branch and ScummVM 2.1.0git3428-gc518691d7c (Aug 12 2018 19:04:49).