scale.js Example File | Qt Script

Qt 5.9 | Qt Script | Context2D Example | scale.js Example File

Qt 5.9.3 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();
      }