efficient way to compare 2 images?

[SMcNeill]

Code: (Select All)

Print _Alpha32(_RGB32(150, 0, 0)), _Alpha32(_RGB32(150, 0, 0, 0))

Print _Alpha32(_RGB32(150, 0, 0)), _Alpha32(_RGB32(150, 0, 0, 255))

Yes??  Is there a question in there somewhere?

_RGBA32 has no trouble giving you a zero alpha color value.   But you having PSET that color onto your screen where it's blended with anything yet....   It's the PSET atop another color where the blending occurs, resulting in a 255 alpha color from the mixture.