[GR32] How to blend two TBitmap32s

[WojTec]

I don't know how to blend two bitmaps if these bitmaps are not layers. For layers I'm using OnPixelCombine with assigned procedures like this:

procedure Multiply(F: TColor32; var B: TColor32; M: TColor32);

I tried this:

Delphi-Quellcode:

function ColorAlgebra(F, B, M: TColor32): TColor32;
begin
  BlendMode.Multiply(F, B, M);  // the same procedure for OnPixelCombine
  Result := BlendRegEx(F, B, M);
end;

BlendTransfer(Blended, 0, 0, Blended.BoundsRect, ImageMap, ImageMap.BoundsRect,
  ShapeMap, ShapeMap.BoundsRect, ColorAlgebra, 200
);

but MasterAlpha parasm work diffrent than master alpha in top layer (opacity). This param decide which bitmap should be more visible (0 = first, 255 = second). How to blend bitmaps like layers?

[Namenloser]

Why so complicated? I've always simply done it like this:

Delphi-Quellcode:

var
  A,B: TBitmap32;
begin
  [...]
  A.MasterAlpha := 127; // 50%
  A.DrawMode := dmBlend;
  A.DrawTo(B, 0, 0);
  // B now contains the blended image
  [...]

[WojTec]

Delphi-Quellcode:

    ImageMap.DrawMode := dmBlend;
    ImageMap.OnPixelCombine := BlendMode.Multiply;
    ImageMap.MasterAlpha := 0;
    ImageMap.DrawTo(ShapeMap, 0, 0);

    Image321.Bitmap.Assign(ShapeMap);

I tried and effect is identical.

[Namenloser]

What effect is identical? It'd really help if you were more specific about what you want to achieve and what is happening instead.

[mkinzler]

Perhaps show a screenshot or similar

[WojTec]

Ok guys, please look at attached picture:

I want to blend 2 with 1 and get 5. In my method I got 3, in @NamenLozer's method I got 4. In my program that suppots layers I got 5 and this is valid effct (opacity is 100%, white is not visible). Are you understand what I mean? I want to get 5 effect without layers.

@mkinzler, thanks for advise