</body>
<script type="text/javascript">
var canvas = document.getElementById("mycanvas");
var context = canvas.getContext("2d");
//用黑色直线线表示开始的x/y轴
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.lineTo(800,0);
context.stroke();
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.lineTo(0,800);
context.stroke();
//原矩形：蓝色
context.beginPath();
context.fillStyle = "cornflowerblue";
context.fillRect(0,0,50,50);
context.fill();
//平移矩形：粉色
context.beginPath();
context.translate(200,0) //正：往右、下
context.fillStyle = "deeppink";
context.fillRect(0,0,50,50);
context.fill();
//用蓝色直线表示平移以后的坐标轴
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.lineTo(400,0);
context.stroke();
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.lineTo(0,400);
context.stroke();
</script>
</html>
得到如下效果：证明图形变换以后是改变了坐标系的
2、旋转
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
canvas{
border:1px solid red;
}
</style>
</head>
<body>
<canvas id="mycanvas" width="800" height="800"></canvas>
</body>
<script type="text/javascript">
var canvas = document.getElementById("mycanvas");
var context = canvas.getContext("2d");
//用黑色直线表示平移以后的坐标轴
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 10;
context.lineTo(800,0);
context.stroke();
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 10;
context.lineTo(0,800);
context.stroke();
//原图：蓝色
context.beginPath();
context.fillStyle = "cornflowerblue";
context.fillRect(100,0,50,50);
context.fill();
//旋转：绿色
context.beginPath();
context.fillStyle = "limegreen";
context.rotate(Math.PI/4);
context.fillRect(100,0,50,50);
//用蓝色直线表示平移以后的坐标轴
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.strokeStyle = "blue";
context.lineTo(800,0);
context.stroke();
context.beginPath();
context.moveTo(0,0);
context.lineWidth = 5;
context.strokeStyle = "blue";
