Delphi 7, how to copy Paintbox content to a Tbitmap? - delphi

Question

im working on delphi 7 and i want to how to copy/assign the content of a TpaintBox to a Tbitmap?
like this
public
{ Public declarations }
BitMap : TBitmap;
end;
i have a Tbitmap declared as public and i create it onFormCreate like this
procedure TForm1.FormCreate(Sender: TObject);
begin
BitMap := TBitMap.Create;
end;
Then i draw somthing on the bitmap like this
procedure TForm1.DrawOnPainBox;
begin
If BitMap.Width <> PaintBox1.Width then BitMap.Width := PaintBox1.Width;
If BitMap.Height <> PaintBox1.Height then BitMap.Height := PaintBox1.Height;
BitMap.Canvas.Rectangle(0,0,random(PaintBox1.Width ),random(PaintBox1.Height));
PaintBox1.Canvas.Draw(0,0,BitMap);
end;
with PaintBox1.Canvas.Draw(0,0,BitMap); we can display what is there in Bitmap to a paintbox but what is the reverse way?
how to assign/copy content of a paintbox to a bitmap?
`BitMap:=PaintBox1.Canvas.Brush.Bitmap;`
this compiles but if i do this and again call the procedure TForm1.DrawOnPainBox; i get access Violation and the debugger show the bitmap and PaintBox1.Canvas.Brush.Bitmap even though some lines are drawn on the paintBox

Answer 1

To assign the contents of a TPaintBox (let's call it PaintBox1) to a TBitmap (Bitmap, say), you can do
Bitmap.Width := PaintBox1.Width;
Bitmap.Height := PaintBox1.Height;
BitBlt(Bitmap.Canvas.Handle,
0,
0,
Bitmap.Width,
Bitmap.Height,
PaintBox1.Canvas.Handle,
0,
0,
SRCCOPY);
Notice: In newer versions of Delphi, you can use Bitmap.SetSize instead of Bitmap.Width and Bitmap.Height.

Answer 2

TBitmap.setsize has been introduced in Delphi 2006, you may be using an older version. Just replace
Bitmap.SetSize (X, Y)
by
Bitmap.Width := X
Bitmap.Height := Y
it's slower (but it matters only if you use it in a loop), but you will compile the code
if this happens too often, declare a new unit BitmapSize.pas:
unit BitmapSize;
interface
uses
graphics;
Type
TBitmapSize = class (TBitmap)
public
procedure Setsize (X, Y : integer);
end;
implementation
procedure TBitmapsize.Setsize(X, Y: integer);
begin
Width := X; // may need some more tests here (X > 0, Y > 0, ...)
Height := Y;
end;
end.
then replace in declaration and creation of your bitmap TBitmap with TBitmapSize.
..
Var
B : TBitmapSize;
..
B := TBitmapSize.Create;