Mega Code Archive
How to handle bitmap layers
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Title: How to handle bitmap layers?
Question: I want overlay bitmap2 over bitmap. The bitmap2 should be on top of bitmap1,
i.e. the end result should be that bitmap2 should also show bits of bitmap1.
What is the best way in Delphi to handle this?
Answer:
There are two methods. One works using a TImageList the other without. So the
latter will work with other file types besides BMP's. Here's the code for both,
it's pretty clear how both work. The key thing is you must specify a
transparent color:
procedure DrawTrans(DestCanvas: TCanvas; X,Y: smallint; SrcBitmap:
TBitmap; AColor: TColor);
var
ANDBitmap, ORBitmap: TBitmap;
CM: TCopyMode;
Src: TRect;
begin
ANDBitmap:= NIL;
ORBitmap:= NIL;
try
ANDBitmap:= TBitmap.Create;
ORBitmap:= TBitmap.Create;
Src := Bounds(0,0, SrcBitmap.Width, SrcBitmap.Height);
with ORBitmap do begin
Width:= SrcBitmap.Width;
Height:= SrcBitmap.Height;
Canvas.Brush.Color := clBlack;
Canvas.CopyMode := cmSrcCopy;
Canvas.BrushCopy(Src, SrcBitmap, Src, AColor);
end;
with ANDBitmap do begin
Width:= SrcBitmap.Width;
Height:= SrcBitmap.Height;
Canvas.Brush.Color := clWhite;
Canvas.CopyMode := cmSrcInvert;
Canvas.BrushCopy(Src, SrcBitmap, Src, AColor);
end;
with DestCanvas do begin
CM := CopyMode;
CopyMode := cmSrcAnd;
Draw(X,Y, ANDBitmap);
CopyMode := cmSrcPaint;
Draw(X,Y, ORBitmap);
CopyMode := CM;
end;
finally
ANDBitmap.Free;
ORBitmap.Free;
end;
end;
The other way:
abitmap:= tbitmap.Create;
imagelist1.Clear;
abitmap.LoadFromFile('1.bmp');
imagelist1.AddMasked(abitmap, clNone);
abitmap.Empty;
abitmap.LoadFromFile('e1.bmp');
imagelist1.AddMasked(abitmap, clWhite);
abitmap.Empty;
abitmap.LoadFromFile('h1.bmp');
imagelist1.AddMasked(abitmap, clWhite);
imagelist1.Draw(image1.Canvas, 0, 0, 0);
imagelist1.Draw(image1.Canvas, 0, 0, 1);
imagelist1.Draw(image1.Canvas, 0, 0, 2);
abitmap.free;
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