[Graphic] Why the color of image component become black?

[brant_chen]

I use default settings for my Image component.
Once I add code to mouseclick event of image component, the background color become black.
Why?

Code: [Select]

procedure Tf_main.Image1Click(Sender: TObject);
begin
  Image1.Canvas.Pen.Color:=clRed;
  Image1.Canvas.Line(1,1,800,600);
end;
With above code, when launching program, the background color of image1 is clWindows, once I click on it, it become black and draw a line in Red.
How could I do to prevent changing the background? Where does the black come?
Thank you.

[brant_chen]

ok, I find the answer by myself.

The default brush color for image component is clblack.
I need set it to clWindow or any other, then, I need fillrect for image component, like below:

Code: [Select]


  Image1.Canvas.Brush.Color:=clgreen;
  Image1.Canvas.FillRect(image1.BoundsRect);         


[Blaazen]

There is:

Code: [Select]

Image.Canvas.Clear;

[brant_chen]

There is:

Code: [Select]

Image.Canvas.Clear;

Thank you
It's a good habit clearing canvas before you do a dozen of whole new things.