BGRABitmap tutorial 6

│ Deutsch (de) │ English (en) │ español (es) │ français (fr) │

This tutorial shows you how to use different line styles and shapes.

Create a new project

Create a new project and add a reference to BGRABitmap, the same way as in the first tutorial.

Add a painting handler

With the object inspector, add an OnPaint handler and write : <delphi>procedure TForm1.FormPaint(Sender: TObject); var image: TBGRABitmap;

   c: TBGRAPixel;

begin

 image := TBGRABitmap.Create(ClientWidth,ClientHeight,ColorToBGRA(ColorToRGB(clBtnFace)));
 c := ColorToBGRA(ColorToRGB(clWindowText)); 

 image.RectangleAntialias(80,80,300,200,c,50);

 image.Draw(Canvas,0,0,True);
 image.free;

end;</delphi>

Run the program

This should draw a rectangle with a wide black pen.

Change join style

If you want round corners, you can specify : <delphi> image.JoinStyle := pjsRound;</delphi>

Run the program

This should draw a rectangle with a wide black pen with rounded corners.

Mix join styles

You can mix join styles for a rectangle like this: <delphi> image.FillRoundRectAntialias(80,80,300,200, 20,20, c, [rrTopRightSquare,rrBottomLeftSquare]); </delphi>

This function use round corners by default, but you can override it with square corners or bevel corners. You should obtain the following image.

Change pen style

You can draw a dotted line like this : <delphi> image.JoinStyle := pjsBevel;

   image.PenStyle := psDot;
   image.DrawPolyLineAntialias([PointF(40,200), PointF(120,100), PointF(170,140), PointF(250,60)],c,10);

</delphi>

You should obtain the following image. Notice that line begins with a round cap.

Change line cap

You can draw a polyline with a square cap like this : <delphi> image.JoinStyle := pjsBevel;

   image.LineCap := pecSquare;
   image.PenStyle := psSolid;
   image.DrawPolyLineAntialias([PointF(40,200), PointF(120,100), PointF(170,140), PointF(250,60)],c,10);

</delphi>

Opened line drawing

You can draw a line which is opened, i.e. the end of the line is rounded inside.

<delphi> image.DrawPolyLineAntialias([PointF(40,200), PointF(120,100), PointF(170,140), PointF(250,60)],c,10,False);</delphi>

This way you can connect lines one after another without drawing the junction twice, which is useful with semi-transparent drawing. You can compare it like this: <delphi> c := BGRA(0,0,0,128);

   image.DrawLineAntialias(40,150, 120,50, c, 10);
   image.DrawLineAntialias(120,50, 170,90, c, 10);
   image.DrawLineAntialias(170,90, 250,10, c, 10);

   image.DrawLineAntialias(40,250, 120,150, c, 10, False);
   image.DrawLineAntialias(120,150, 170,190, c, 10, False);
   image.DrawLineAntialias(170,190, 250,110, c, 10, True);</delphi>

Previous tutorial (layers and masks) Next tutorial (splines)