Procedure for setting pixel colors.

procedure SetPixel32(const Image: TImageData; 
                     X: LongInt; 
                     Y: LongInt; 
                     const Color: TColor32Rec);

Imaging (at line 247)

Input 32 bit ARGB color is translated to native format and then written to Image. Works for all image formats (except special) so it is not very fast.