TBGRABitmap uses TCanvas rather than TBGRACanvas

[abtaylr]

I am using TBGRABitmap, but when I use one of the procedures I get an error that it expects TBitmap rather than TBGRABitmap.

Code: Pascal  [Select][+][-]

1.      PrevFrameImage:=TBGRABitmap.Create;
2.      PrevSubImage:=TBGRABitmap.Create;
3.      . . . .
4.  

Later, I input PrevSubImage into another TBGRABitmap like this:

Code: Pascal  [Select][+][-]

1.             CharMatrix.SubBmp.Canvas.Draw(0,0,PrevSubImage);
2.             CutRect := CharMatrix.CutValidRect(CharMatrix.SubBmp, 1);
3.             VobProcess.ReallySkip := False;
4.             ImageVideo.Canvas.Draw(0,0,PrevFrameImage);

The error refers to CharMatrix.SubBmp.Canvas.Draw:

      unit21.pas(643,59) Error: Incompatible type for arg no. 3: Got "TBGRAGtkBitmap", expected "TGraphic"

Under the Class -- CharMatrix, SubBmp is created like this:

Code: Pascal  [Select][+][-]

1.     TCharacterMatrix = Class
2.         . . . .
3.        SubBmp : TBGRABitmap;
4.        . . . .
5.     end;
6.  
7.    implementation
8.  
9.     constructor TCharacterMatrix.Create;overload;
10.     begin
11.       . . . .
12.       SubBmp := TBGRABitmap.Create;
13.      . . . .
14.     end;
15.  

CharMatrix is an instance of the TCharacterMatrix Class.  I make extensive use of SubBmp within this class in numerous methods. The place where is the error is made is an input point in the form where CharMatrix has the bitmap introduced.

Following the error, the following note is found:

    canvas.inc(20,19) Hint: Found declaration: Draw(LongInt;LongInt;TGraphic);

Shouldn't that refer to BGRACanvas? I would think that BGRABitmap uses BGRACanvas. Am I missing something?

The note is referring to the TCanvas methods:

Code: Pascal  [Select][+][-]

1. procedure TCanvas.Draw(X, Y: Integer; SrcGraphic: TGraphic);
2. var
3.   ARect: TRect;
4. begin
5.   if not Assigned(SrcGraphic) then exit;
6.   ARect:=Bounds(X,Y,SrcGraphic.Width,SrcGraphic.Height);
7.   StretchDraw(ARect,SrcGraphic);
8. end;

If it was pointed to TBGRACanvas, it should refer to:

Code: Pascal  [Select][+][-]

1. procedure TBGRACanvas.Draw(X, Y: Integer; SrcBitmap: TBGRACustomBitmap);
2. begin
3.   FBitmap.PutImage(X,Y,SrcBitmap,dmDrawWithTransparency);
4. end;

or maybe:

Code: Pascal  [Select][+][-]

1. procedure TBGRAGtkBitmap.Draw(ACanvas: TCanvas; x, y: integer; Opaque: boolean);
2. begin
3.   if self = nil then
4.     exit;
5.   if Opaque then
6.     DrawOpaque(ACanvas, Rect(X, Y, X + Width, Y + Height))
7.   else
8.     DrawTransparent(ACanvas, Rect(X, Y, X + Width, Y + Height));
9. end;
10.  
11. procedure TBGRAGtkBitmap.Draw(ACanvas: TCanvas; Rect: TRect; Opaque: boolean);
12. begin
13.   if self = nil then
14.     exit;
15.   if Opaque then
16.     DrawOpaque(ACanvas, Rect)
17.   else
18.     DrawTransparent(ACanvas, Rect);
19. end;

As you can see these refer to TCanvas.

I am using Kubuntu 16.04 LTS 64bit.  FPC 3.0.1 (fixes branch)  Lazarus 1.6.1 (fixes branch).

[lainz]

Later, I input PrevSubImage into another TBGRABitmap like this:

Code: Pascal  [Select]
            CharMatrix.SubBmp.Canvas.Draw(0,0,PrevSubImage);
            CutRect := CharMatrix.CutValidRect(CharMatrix.SubBmp, 1);
            VobProcess.ReallySkip := False;
            ImageVideo.Canvas.Draw(0,0,PrevFrameImage);

That's not the way to input PrevSubImage into other. You need to use PutImage, BlendImage or BlendImageOver methods. Don't use Canvas.Draw.

[abtaylr]

Excellent! A much better method than what I was doing!  Thx.

[circular]

If you would like to use functions similar to TCanvas, you can use the CanvasBGRA property that provides functions with similar to TCanvas.

The property Canvas is provided only for compatibility with TBitmap and but it is recommended to avoid using it and to use functions like PutImage as Lainz suggests or the properties CanvasBGRA or Canvas2D.