Merge

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function MergeReg(F, B: TColor32): TColor32;

procedure MergeMem(F: TColor32; var B: TColor32);

Description

Merges a foregrownd (F) color with the background color (B) using the alpha component of the foreground color. It does merge the alpha-channels.

SA = 1 - (1 - FA) (1 - BA)

SRGB = (FA * FRGB + BA * (1 - FA) * BRGB) / SA

MergeReg takes parameters and produces the result operating on CPU registers.

MergeMem operates with the background color referenced by a memory address.

Note, that after using the Merge function, you have to call EMMS. Otherwise CPU will be unable to handle floating point instructions.