Difference between revisions of "Drawing with canvas"

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m (Correct canvas image)
 
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* [[Canvas ellipse]], draws an ellipse in a rectangle defined by (x1,y1) and (x2,y2). If x2-x1 = y2-y1, the ellipse will be a circle with radius (x2-x1)/2.
 
* [[Canvas ellipse]], draws an ellipse in a rectangle defined by (x1,y1) and (x2,y2). If x2-x1 = y2-y1, the ellipse will be a circle with radius (x2-x1)/2.
  
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In the Canvas object the <code>Brush</code> and <code>Pen</code> objects are defined, both with a <code>Color</code> 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 color, before giving the instruction to draw, the order of the statements is important. This would be the code, notice how the color is changed before drawing the ellipse:
  
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The following code draws the diagonals of the canvas. Enter the code between ''begin'' and ''end'' of the procedure Button1Click:
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<syntaxhighlight lang=pascal>
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  Canvas.Brush.Color:= clRed;
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<syntaxhighlight>
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  Canvas.Ellipse(195, 117, 205, 128);
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procedure TForm1.Button1Click(Sender: TObject);
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  Canvas.Brush.Color:= clBlue;
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begin
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  Canvas.Rectangle (192, 130,208,160);
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   canvas.Line(0,0, form1.Width,form1.Height);
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  Canvas.Brush.Color:= clGreen;
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   canvas.Line(0,form1.height,form1.width,0);
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  Canvas.Rectangle (187, 130,191,162);
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end;
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  Canvas.Brush.Color:= clYellow;
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   Canvas.Rectangle (209, 130,213,162);
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  Canvas.Brush.Color:= clMaroon;
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   Canvas.Rectangle (193,161,199,200);
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  Canvas.Brush.Color:= clPurple;
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  Canvas.Rectangle (201,161,207,200);
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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In the Canvas object the ''Brush'' and ''Pen'' objects are defined, 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 color, before giving the instruction to draw, the order of the statements is important. This would be the code, notice how the color is changed before drawing the ellipse:
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or shorter:
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−
<syntaxhighlight>
 
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  canvas.Brush.color:= clred;
 
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  canvas.Ellipse(195, 117, 205, 128);
 
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  canvas.Brush.color:= clblue;
 
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  canvas.Rectangle (192, 130,208,160);
 
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  canvas.Brush.color:= clgreen;
 
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  canvas.Rectangle (187, 130,191,162);
 
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  canvas.Brush.color:= clyellow;
 
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  canvas.Rectangle (209, 130,213,162);
 
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  canvas.Brush.color:= clmaroon;
 
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  canvas.Rectangle (193,161,199,200);
 
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  canvas.Brush.color:= clpurple;
 
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  canvas.Rectangle (201,161,207,200);
 
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</syntaxhighlight>
 
  
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or shorter
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<syntaxhighlight lang=pascal>
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<syntaxhighlight>
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   with Canvas do begin
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   with canvas do begin
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     Brush.Color:= clRed;
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     Brush.color:= clred;
 
 
     Ellipse(195, 117, 205, 128);
 
     Ellipse(195, 117, 205, 128);
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     Brush.color:= clblue;
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     Brush.Color:= clBlue;
 
     Rectangle (192, 130,208,160);
 
     Rectangle (192, 130,208,160);
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     Brush.color:= clgreen;
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     Brush.Color:= clGreen;
 
     Rectangle (187, 130,191,162);
 
     Rectangle (187, 130,191,162);
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     Brush.color:= clyellow;
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     Brush.Color:= clYellow;
 
     Rectangle (209, 130,213,162);
 
     Rectangle (209, 130,213,162);
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     Brush.color:= clmaroon;
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     Brush.Color:= clMaroon;
 
     Rectangle (193,161,199,200);
 
     Rectangle (193,161,199,200);
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     Brush.color:= clpurple;
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     Brush.Color:= clPurple;
 
     Rectangle (201,161,207,200);
 
     Rectangle (201,161,207,200);
 
   end;
 
   end;
Line 53: Line 43:
  
 
This will give something like this:  
 
This will give something like this:  
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[[Image:canvas3.png]]
+
[[Image:canvas.png]]

Latest revision as of 23:35, 27 February 2021

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Drawing with canvas can be done using several procedures e.g.

  • Canvas line, draws a line from coordinates (x1,y1) to (x2,y2)
  • Canvas rectangle, draws a rectangle from upper left (x1,y1) to lower right (x2,y2)
  • Canvas ellipse, draws an ellipse in a rectangle defined by (x1,y1) and (x2,y2). If x2-x1 = y2-y1, the ellipse will be a circle with radius (x2-x1)/2.

In the Canvas object the Brush and Pen objects are defined, 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 color, before giving the instruction to draw, the order of the statements is important. This would be the code, notice how the color is changed before drawing the ellipse: 

  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);

or shorter: 

  with Canvas do begin
    Brush.Color:= clRed;
    Ellipse(195, 117, 205, 128);
    Brush.Color:= clBlue;
    Rectangle (192, 130,208,160);
    Brush.Color:= clGreen;
    Rectangle (187, 130,191,162);
    Brush.Color:= clYellow;
    Rectangle (209, 130,213,162);
    Brush.Color:= clMaroon;
    Rectangle (193,161,199,200);
    Brush.Color:= clPurple;
    Rectangle (201,161,207,200);
  end;

This will give something like this: canvas.png

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