image buffer implementation in delphi

Question

Context

I am drawing to a canvas, this is updated regularly and it flashes. Logically thinking I assumed this is because my redraw method clears the Canvas then draws one element at a time to the canvas. so my idea was to write to a Timage then set the picture to the Timage.

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Information

here is my code

procedure Tmainwindow.Button3Click(Sender: TObject);
var bufferpicture:TImage;
begin

//draw stuff to bufferpicture
  //***
//draw stuff to bufferpicture

myrealpicture.picture:=bufferpicture.picture;

end;

Upon running the code I get a error show below.

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Question How do I set the canvas of one to another since canvas is a read only property? or is there a better way to do what i am trying to do?

Answer 1

use the DoubleBuffered property

Answer 2

1. It looks like you did not create myrealpicture

2. I would use the method Assign

   MyRealPicture.Picture.Assign(BufferPicture.Picture);

3. You can copy the content of one canvas to another using BitBlt:

   var
     BackBuffer: TBitmap;
   begin
     BackBuffer := TBitmap.Create;
     try
       { drawing stuff goes here}
       BitBlt(Form1.Canvas.Handle, 0, 0, BackBuffer.Width, BackBuffer.Height,
           BackBuffer.Canvas.Handle, 0, 0, SRCCOPY);
     finally
       BackBuffer.Free;
     end;
   end;
   

4. You can just use the DoubleBuffered property