Drawing with canvas

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published by leo_tecnologica@yahoo.com.ar --- Leonardo Gabriel Calautti

Line (x1, y1, x2, y2)-> draw a line from point (x1, y1) to (x2, y2)

Rectangle (x1, y1, x2, y2)-> draw a rectangle with a vertex at the point (x1, y1) and the opposite at the point (x2, y2)

Ellipse (x1, y1, x2, y2)-> draws an ellipse in the rectangle defined by the point (x1, y1) and point (x2, y2)


For example, the following code draws the diagonals. Enter the code between the begin and the end of the function Button1Click:

procedure TForm1.Button1Click(Sender: TObject);
  canvas.Line(0,0, form1.Width,form1.Height);

How can you paint the inside of the rectangles and ellipses? There in the Canvas object, an object called Brush and a Pen, both with a color property, which indicate the color that makes the fill and stroke of the various objects that are drawn. To paint an object of one color, the first thing is to change the brush and brush, before giving the instruction to draw ... the order is important. This would be our code, notice how the color is changed first and then given the instruction to draw:

   canvas.Brush.color:= clred;
   canvas.Ellipse(195, 117, 205, 128);
   canvas.Brush.color:= clblue;
   canvas.Rectangle (192, 130,208,160);
   canvas.Brush.color:= clgreen;
   Canvas.Rectangle (187, 130,191,162);
   canvas.Brush.color:= clyellow;
   Canvas.Rectangle (209, 130,213,162);
   canvas.Brush.color:= clmaroon;
   Canvas.Rectangle (193,161,199,200);
   canvas.Brush.color:= clpurple;
   Canvas.Rectangle (201,161,207,200);

If you follow the steps, you may have done something like this:canvas3.png