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();
 }
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