scale.js Example File | Qt Script

- Qt 5.4
- Qt Script
- Context2D Example
- scale.js Example File
- Qt 5.4.2 Reference Documentation

# scale.js Example File

script/context2d/scripts/scale.js

    var ctx = document.getElementById('tutorial').getContext('2d');
      ctx.strokeStyle = "#fc0";
      ctx.lineWidth = 1.5;
      ctx.fillRect(0,0,300,300);

      // Uniform scaling
      ctx.save()
      ctx.translate(50,50);
      drawSpirograph(ctx,22,6,5);  // no scaling

      ctx.translate(100,0);
      ctx.scale(0.75,0.75);
      drawSpirograph(ctx,22,6,5);

      ctx.translate(133.333,0);
      ctx.scale(0.75,0.75);
      drawSpirograph(ctx,22,6,5);
      ctx.restore();

      // Non uniform scaling (y direction)
      ctx.strokeStyle = "#0cf";
      ctx.save()
      ctx.translate(50,150);
      ctx.scale(1,0.75);
      drawSpirograph(ctx,22,6,5);

      ctx.translate(100,0);
      ctx.scale(1,0.75);
      drawSpirograph(ctx,22,6,5);

      ctx.translate(100,0);
      ctx.scale(1,0.75);
      drawSpirograph(ctx,22,6,5);
      ctx.restore();

      // Non uniform scaling (x direction)
      ctx.strokeStyle = "#cf0";
      ctx.save()
      ctx.translate(50,250);
      ctx.scale(0.75,1);
      drawSpirograph(ctx,22,6,5);

      ctx.translate(133.333,0);
      ctx.scale(0.75,1);
      drawSpirograph(ctx,22,6,5);

      ctx.translate(177.777,0);
      ctx.scale(0.75,1);
      drawSpirograph(ctx,22,6,5);
      ctx.restore();
    function drawSpirograph(ctx,R,r,O){
      var x1 = R-O;
      var y1 = 0;
      var i  = 1;
      ctx.beginPath();
      ctx.moveTo(x1,y1);
      do {
        if (i>20000) break;
        var x2 = (R+r)*Math.cos(i*Math.PI/72) - (r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))
        var y2 = (R+r)*Math.sin(i*Math.PI/72) - (r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))
        ctx.lineTo(x2,y2);
        x1 = x2;
        y1 = y2;
        i++;
      } while (x2 != R-O && y2 != 0 );
      ctx.stroke();
    }