Hallo Christian,
Zitat:
Specifies the boundaries of the clipping rectangle.
property ClipRect: TRect;
Description
Use ClipRect to determine where the canvas needs painting. ClipRect limits the drawing region of the canvas so that any drawing that occurs at coordinates outside the ClipRect is clipped and doesn’t appear in the image.
When handling a form’s OnPaint event, the canvas' ClipRect property is set to the rectangle that needs to be painted. Portions of the image that do not overlap the ClipRect do not need to be drawn. Thus, OnPaint routines can use the value of ClipRect to optimize painting, speeding the overall performance of the application.
Beispiel:
Delphi-Quellcode:
This example creates a region and selects this region as the clipping rectangle for the Image component's canvas. It then sets the canvas's brush color to red and calls FillRect using the ClipRect as the area to fill. Lastly, the ClipRect is reset to the original value that it contained by calling SelectClipRect with nil as the second parameter and deletes the region.
procedure Form1.Button1Click(Sender: TObject);
var
MyRgn: HRGN ;
begin
MyRgn := CreateRectRgn(100,100,200,200);
SelectClipRgn(Image1.Canvas.Handle,MyRgn);
Image1.Canvas.Brush.Color := clRed;
Image1.Canvas.FillRect(Image1.Canvas.ClipRect);
Image1.Invalidate;
SelectClipRgn(Image1.Canvas.Handle,nil);
DeleteObject(MyRgn);
end;
Grüsse, Daniel
