BGRABitmap tutorial 6

From Lazarus wiki
Revision as of 01:54, 2 January 2020 by Trev (talk | contribs) (Fixed syntax highlighting)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

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

Home | Tutorial 1 | Tutorial 2 | Tutorial 3 | Tutorial 4 | Tutorial 5 | Tutorial 6 | Tutorial 7 | Tutorial 8 | Tutorial 9 | Tutorial 10 | Tutorial 11 | Tutorial 12 | Tutorial 13 | Tutorial 14 | Tutorial 15 | Tutorial 16 | Edit

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:

procedure TForm1.FormPaint(Sender: TObject);
var image: TBGRABitmap;
    c: TBGRAPixel;
  image := TBGRABitmap.Create(ClientWidth,ClientHeight,ColorToBGRA(ColorToRGB(clBtnFace)));
  c := ColorToBGRA(ColorToRGB(clWindowText)); 



Run the program

This should draw a rectangle with a wide black pen.


Change join style

If you want round corners, you can specify:

    image.JoinStyle := pjsRound;

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:

    image.FillRoundRectAntialias(80,80,300,200, 20,20, c, [rrTopRightSquare,rrBottomLeftSquare]);

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:

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

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:

    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);


Opened line drawing

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

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


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:

    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);


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