例如：
function drawScreen() {
//now draw a red square
context.setTransform(1,0,0,1,0,0);var angleInRadians = 45 * Math.PI / 180;
context.rotate(angleInRadians);
context.fillStyle = "red";
context.fillRect(100,100,50,50);
}
function drawScreen() {
//now draw a red square
context.setTransform(1,0,0,1,0,0);var angleInRadians = 45 * Math.PI / 180;
context.rotate(angleInRadians);
context.fillStyle = "red";
context.fillRect(100,100,50,50);
}
1 transform(m11, m12, m21, m22, dx, dy)
This method changes the transformation matrix to apply the matrix given by the arguments.
2 setTransform(m11, m12, m21, m22, dx, dy)
This method changes the transformation matrix to the matrix given by the arguments .
The transform(m11, m12, m21, m22, dx, dy) method must multiply the current transformation matrix with the matrix described by:m11 m21 dx
m12 m22 dy
0 0 1
The setTransform(m11, m12, m21, m22, dx, dy) method must reset the current transform to the identity matrix, and then invoke the transform(m11, m12, m21, m22, dx, dy) method with the same arguments.Example:
Following is a simple example which makes use of transform() and setTransform() methods:<!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'); var sin = Math.sin(Math.PI/6);
var cos = Math.cos(Math.PI/6);
ctx.translate(200, 200);
var c = 0;
for (var i=0; i <= 12; i++) {
c = Math.floor(255 / 12 * i);
ctx.fillStyle = "rgb(" + c + "," + c + "," + c + ")";
ctx.fillRect(0, 0, 100, 100);
ctx.transform(cos, sin, -sin, cos, 0, 0);
}
ctx.setTransform(-1, 0, 0, 1, 200, 200);
ctx.fillStyle = "rgba(100, 100, 255, 0.5)";
ctx.fillRect(50, 50, 100, 100);
}else {
alert('You need Safari or Firefox 1.5+ to see this demo.');
}
}
</script>
</head>
<body onload="drawShape();">
<canvas id="mycanvas" width="400" height="400"></canvas>
</body>
</html>