How to draw Rectangle in TBGRAVirtualScreen.ReDraw
lazarus / 39-Graphics

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freeman35 · 2014-09-29 14:08

in TBGRAVirtualScreen.ReDraw:
Bitmap.CanvasBGRA.Rectangle(FNewRect, False); "Filled" Parameter is
False but still draw in Rectangle

question is:
How to draw just Rectangle lines in BGRA?
Example code for TImage

Code: [Select]   with Bitmap.Canvas do begin
      Pen.Mode := pmNotXOR;
      Pen.Color := clBlue;
      Pen.Width := 3;
      with FNewRect do Rectangle(Left, Top, Right, Bottom);
   end;

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circular · 2014-09-29 21:24

Ah I guess that's a bug. I have applied some fix on subversion.

You can in all cases draw just the frame by setting
CanvasBGRA.Brush.Style := bsClear just as you would do with usual
TCanvas.

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freeman35 · 2014-10-01 08:50

Thank you very much, this code(s) working for me.

Code: [Select] Bitmap.PutImage(0, 0, content, dmDrawWithTransparency);
with FNewRect do begin
   if (left>0)and(Right>0)then begin
    //Bitmap.CanvasBGRA.Pen.Color := clBlue;
    //Bitmap.CanvasBGRA.Pen.Width := 3;   
   //Bitmap.CanvasBGRA.Rectangle(FNewRect, False); //--> Fixed

    Bitmap.CanvasBGRA.Brush.Style := bsClear;
    with Bitmap.Canvas do begin
       Pen.Mode := pmNotXOR;
       Pen.Color := clBlue;
       Pen.Width := 3;
       Rectangle(Left, Top, Right, Bottom);
    end;
   end;
 end;
And I found different way too
Code: [Select]....
var   FNewRect : TRect;
......
content := TBGRABitmap.Create('imga.bmp');
.....
procedure TForm1.BGRAVirtualScreen1Redraw(Sender: TObject; Bitmap:
TBGRABitmap);
var ctx: TBGRACanvas2D;
begin
  ctx := Bitmap.Canvas2D;
  //ctx.antialiasing := False;
  Bitmap.PutImage(0, 0, content, dmDrawWithTransparency);
    if (FNewRect.left>0)and(FNewRect.Right>0)then begin
      ctx.lineWidth := 2;
      ctx.lineStyle([2,2]);
      ctx.strokeStyle(clBlue);
      ctx.strokeRect(FNewRect.Left, FNewRect.Top, FNewRect.Right,
FNewRect.Bottom);
  end;
end;

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circular · 2014-10-03 19:52

I would not recommend to use Bitmap.Canvas because it is more provided
as a workaround in case you cannot use CanvasBGRA and can be slow.

Normally the following should do just fine:
Code: [Select]   Bitmap.CanvasBGRA.Pen.Color := clBlue;
   Bitmap.CanvasBGRA.Pen.Width := 3;   
   Bitmap.CanvasBGRA.Brush.Style := bsClear;
   Bitmap.CanvasBGRA.Rectangle(FNewRect);
Or, even simpler:
Code: [Select]   Bitmap.Rectangle(FNewRect, clBlue);
Or:
Code: [Select]   Bitmap.RectangleAntialias(FNewRect.Left,FNewRect.Top,
FNewRect.Right,FNewRect.Bottom, CSSBlue, 3);