[SOLVED] BGRA library: Where am I going wrong?

[EganSolo]

I am trying to adapt the aa-demo program of the BGRA library to my own use. I've included the small project I've been working with, but here's the highlight:

1. I've declared the following form:

Code: Pascal  [Select][+][-]

1.    TForm1 = class(TForm)
2.       Label1: TLabel;
3.       Label2: TLabel;
4.       Label_PixelSizeValue: TLabel;
5.       Panel1: TPanel;
6.       SpinEdit_Gamma: TFloatSpinEdit;
7.       TrackBar_PixelSize: TTrackBar;
8.       procedure FormCreate(Sender: TObject);
9.       procedure FormPaint(Sender: TObject);
10.    private
11.       fpts: array[1..4] of TPointF;
12.       fPixelSize : Integer;
13.       fMovingPointIndex : integer;
14.       function coordToBmp(pt: TPointF): TPointF;
15.    public
16.  
17.    end;
18.  

The relevant methods are as follows:

Code: Pascal  [Select][+][-]

1. function TForm1.coordToBmp(pt: TPointF): TPointF;
2. begin
3.   result := (pt+PointF(0.5,0.5))*(1/fpixelSize)-PointF(0.5,0.5);
4. end;
5.  

and

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormCreate(Sender: TObject);
2. begin
3.  //Let's try and draw a rectangle.
4.  fpts[1] := PointF(100,100);
5.  fpts[2] := PointF(200,100);
6.  fpts[3] := PointF(200,10 );
7.  fpts[4] := PointF(10 , 10);
8.  Label_PixelSizeValue.Caption := '= ' + IntToStr(TrackBar_PixelSize.Position);
9.  fMovingPointIndex := -1;
10.  SpinEdit_Gamma.Value := BGRAGetGamma;
11. end;
12.  

Finally:

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormPaint(Sender: TObject);
2. var bmp          : TBGRABitmap;
3.     aZoomX       ,
4.     aZoomY       : Integer    ;
5.     tx, ty       : Integer    ;
6. begin
7.   aZoomX       := ClientWidth;
8.   aZoomY       := Panel1.Top ;
9.   fPixelSize   := TrackBar_PixelSize.Position;
10.   tx           := (aZoomX + fPixelSize - 1) div fPixelSize;
11.   ty           := (aZoomY + fPixelSize - 1) div fPixelSize;
12.   //Draw Square
13.   bmp := TBGRABitmap.Create(tx,ty,BGRAWhite);
14.   bmp.RectangleAntialias({x =} 10, {y = } 10, {x2 =} 100, {y2 = } 100, {c = } BGRABlack, {w = } 5, {back =} BGRAWhite);
15.   bmp.FillPolyAntialias([CoordToBMP(fpts[1]), coordToBMP(fpts[2]), coordToBMP(fpts[3]), coordToBMP(fpts[4])], BGRABlack);
16.   bmp.Free;
17. end;
18.  

When I run the code, nothing gets painted on the form. What am I doing wrong?

Thanks for any tip and suggestions!

[winni]

Hi!

You forgot to draw on the canvas of the Form:

Code: Pascal  [Select][+][-]

1.   bmp := TBGRABitmap.Create(tx,ty,BGRAWhite);
2.   bmp.RectangleAntialias({x =} 10, {y = } 10, {x2 =} 100, {y2 = } 100, {c = } BGRABlack, {w = } 5, {back =} BGRAWhite);
3.   bmp.FillPolyAntialias([CoordToBMP(fpts[1]), coordToBMP(fpts[2]), coordToBMP(fpts[3]), coordToBMP(fpts[4])], BGRABlack);
4.   //   now it happens
5.   bmp.draw(canvas,0,0);
6.   bmp.Free;
7.  
8.  

A good introduction is the tutorial in 16 steps:

https://wiki.freepascal.org/BGRABitmap_tutorial


Winni

[EganSolo]

Thanks Winni,

That did indeed the trick.

I'm still learning my way through BGRA. Quite a complete and beautiful library but a bit overwhelming when starting. The tutorials are of some help. I am mostly interested in drawing shapes a la visio and connecting them and the only tutorial that seems somewhat applicable is the Canvas2D. Still, I'm making progress.

[winni]

Hi!

If you are working with shapes then indeed the TBGRACanvas2D is your swissknife. 

Look at chapter 14 of the BGRAbitmap tutorial.

Winni