troubleshooting Question

Delphi 7: After many BitBlts to bitmap it doesn't change anymore

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JackJohnsons asked on
DelphiEditors IDEs
12 Comments1 Solution1230 ViewsLast Modified:
Hello experts

I wrote a function to find a color on the screen, it uses bitblt then directly accesses the bitmap in memory. it works fine, but when I call the function in a burst (for i := 0 to 10000 i.e.) the bitmap "hangs". When the screen changes the bitmap doesnt change anymore =/ It's certainly not the way of accessing the bitmap because when I draw the bitmap to another canvas, it reflects the old screen.
Anyone who got an idea why?
unit ColourFinder;
uses Windows, Variants, Graphics, Sysutils, Forms;
  TRGB24 = packed Record
    b,g,r: Byte;
  TRGB24Array = Array [0..MaxInt div SizeOf(TRGB24)-1] of TRGB24;
  PRGB24Array = ^TRGB24Array;
  SBMP : TBitmap; //Search bitmap
  Scanlines: Array of PRGB24Array; //scanlines
  I: Integer; //for for loop for getting the scanlines
function FindColor(var x, y: Integer; color, xs, ys, xe, ye: Integer; ClientDC : HDC): Boolean;
function FindColor(var x, y: Integer; color, xs, ys, xe, ye: Integer; ClientDC : HDC): Boolean;
  xx, yy: Integer;
  R, G, B: Byte;
  R:= color;
  G:= color shr 8;
  B:= color shr 16;
  BitBlt(SBMP.Canvas.Handle, xs, ys, xe - xs, ye - ys, ClientDC, xs, ys, SRCCOPY);
  for yy:= ys to ye do
    for xx:= xs to xe do
      if(Scanlines[yy][xx].R = R)then if(Scanlines[yy][xx].G = G)then if(Scanlines[yy][xx].B = B)then
        x:= xx;
        y:= yy;
        Result:= True;
  Result:= False;
  x:= -1;
  y:= -1;
  SBMP := TBitmap.Create; //Create the search bitmap
  SBMP.Width:= Screen.Width;
  SBMP.Height:= Screen.Height;
  SetLength(Scanlines, SBMP.Height);
  SBMP.PixelFormat:= pf24bit;
  for I:= 0 to SBMP.Height - 1 do
    Scanlines[i]:= SBMP.ScanLine[i];
  ClientDC := GetDC(0);
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