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HTML5 canvas provides translate(x, y) method which is used to move the canvas and its origin to a different point in the grid.
Here argument x is the amount the canvas is moved to the left or right, and y is the amount it's moved up or down
Following is a simple example which makes use of above method to draw various Spirographs:
<!DOCTYPE HTML> <html> <head> <script type="text/javascript"> function drawShape(){ // get the canvas element using the DOM var canvas = document.getElementById('mycanvas'); // Make sure we don't execute when canvas isn't supported if (canvas.getContext){ // use getContext to use the canvas for drawing var ctx = canvas.getContext('2d'); ctx.fillRect(0,0,300,300); for (i=0;i<3;i++) { for (j=0;j<3;j++) { ctx.save(); ctx.strokeStyle = "#FF0066"; ctx.translate(50+j*100,50+i*100); drawSpirograph(ctx,10*(j+3)/(j+2),-2*(i+3)/(i+1),10); ctx.restore(); } } }else { alert('You need Safari or Firefox 1.5+ to see this demo.'); } } 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(); } </script> </head> <body onload="drawShape();"> <canvas id="mycanvas" width="400" height="400"></canvas> </body> </html> |
The above example would produce following result:
To learn above concept - Do Online Practice using latest version of either Safari or Opera.
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