Bitmap Image Filters
Subject:   friend Dan Van Bose in Fort Worth explained syntax
Date:   2002-08-11 14:40:41
From:   psheldon
Response to: ah you had given me support by giving me a problem to solve

c = boolean ? a : b

c evaluates to first symbol after ? if boolean true and second expression if false.

So, this sentence commands skipping by an offset if Alpha is there and mixing 3 colors only.

I understand now.