Guardar porción de un TBitmap

[rounin]

SrcRect := Rect(...);

BMP := TBitmap.Create;
Bmp.Width := SrcRect.Right - SrcRect.Left;
Bmp.Height := SrcRect.Bottom - SrcRect.Top;

BMP.Canvas.CopyRect(
Rect(0, 0, BMP.Width, BMP.Height),
ASGScreenCapture1.CaptureDesktop.Canvas,
SrcRect
);

BMP.SaveToFile('c:\bmp.bmp');
BMP.Free;