Qt Reference Documentation

translate.js Example File

script/context2d/scripts/translate.js
   var ctx = document.getElementById('tutorial').getContext('2d');
   ctx.fillRect(0,0,300,300);
   for (var i=0;i<3;i++) {
     for (var j=0;j<3;j++) {
       ctx.save();
       ctx.strokeStyle = "#9CFF00";
       ctx.translate(50+j*100,50+i*100);
       drawSpirograph(ctx,20*(j+2)/(j+1),-8*(i+3)/(i+1),10);
       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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