Qt 4.7: scale.js Example File (script/context2d/scripts/scale.js)

Qt 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();
     }