HTML5 Canvas中提供了实现图形平移，旋转，放缩的API。 **平移(translate)** 平移坐标translate(x, y)意思是把(0,0)坐标平移到(x, y)，原来的(0,0)坐标则变成(-x, -y) 图示如下：  任何原来的坐标点p(ox, oy)在translate之后的坐标点为p(ox-x, oy-y),其中点(x, y)为平移 点坐标translate(x, y)。 代码演示： ~~~ // translate is move the startpoint to centera and back to top left corner **function**renderText(width, height, context) {    context.translate(width/ 2, height / 2);// 中心点坐标为(0, 0)    context.font="18px Arial";    context.fillStyle="blue";    context.fillText("Please Press <Esc> to Exit Game",5,50);    context.translate(-width/2,-height/2); // 平移恢复(0,0)坐标为左上角    context.fillText("I'm Back to Top",5,50); } ~~~ **放缩(Scale)** Scale(a, b)意思是将对象沿着XY轴分别放缩至a*x,  b*y大小。效果如图示：  ~~~ // translation the rectangle. **function**drawPath(context) {    context.translate(200,200);    context.scale(2,2);// Scale twice size of original shape    context.strokeStyle= "green";    context.beginPath();    context.moveTo(0,40);    context.lineTo(80,40);    context.lineTo(40,80);    context.closePath();    context.stroke(); } ~~~ **旋转(rotate)** 旋转角度rotate(Math.PI/8)  旋转前的坐标p(x, y)在对应的旋转后的坐标P(rx, ry)为 Rx = x * cos(-angle)- y * sin(-angle); Ry = y * cos(-angle) + x * sin(-angle); 旋转90度可以简化为： Rx = y; Ry = -x; Canvas中旋转默认的方向为顺时针方向。演示代码如下： ~~~ // new point.x = x * cos(-angle) -y * sin(-angle), // new point.y = y * cos(-angle) +x * sin(-angle) **function**renderRotateText(context) {    context.font="24px Arial";    context.fillStyle="red";    context.fillText("i'm here!!!",5,50);       // rotate -90 degreee    // context.rotate(-Math.PI/2);    // context.fillStyle="blue";    // context.fillText("i'm here!!!", -400,30);       // rotate 90 degreee    context.rotate(Math.PI/2);    context.fillStyle="blue";    context.fillText("i'm here!!!",350,-420);       console.log(Math.sin(Math.PI/2));       // rotae 90 degree and draw 10 lines    context.fillStyle="green";    **for**(**var**i=0; i<4; i++) {        **var**x = (i+1)*20;        **var**y = (i+1)*60;        **var**newX = y;        **var**newY =-x;         context.fillRect(newX,newY, 200, 6);    } } ~~~ 通常做法是旋转与平移一起使用，先将坐标(0,0)平移到中心位置 translate (width/2, height/2)然后再使用rotate(Math.PI/2)完成旋转 代码示例如下： ~~~ **function**saveAndRestoreContext(context) {    context.save();    context.translate(200,200);    context.rotate(Math.PI/2);    context.fillStyle="black";    context.fillText("2D Context Rotate And Translate", 10, 10);    context.restore();    context.fillText("2D Context Rotate And Translate", 10, 10); } ~~~ **全部JavaScript代码：** ~~~ var tempContext = null; // global variable 2d context window.onload = function() { var canvas = document.getElementById("target"); canvas.width = 450; canvas.height = 450; if (!canvas.getContext) { console.log("Canvas not supported. Please install a HTML5 compatible browser."); return; } // get 2D context of canvas and draw image tempContext = canvas.getContext("2d"); // renderText(canvas.width, canvas.height, tempContext); saveAndRestoreContext(tempContext); // drawPath(tempContext); } // translate is move the start point to centera and back to top left corner function renderText(width, height, context) { context.translate(width / 2, height / 2); context.font="18px Arial"; context.fillStyle="blue"; context.fillText("Please Press <Esc> to Exit Game",5,50); context.translate(-width / 2, -height / 2); context.fillText("I'm Back to Top",5,50); } // translation the rectangle. function drawPath(context) { context.translate(200, 200); context.scale(2,2); // Scale twice size of original shape context.strokeStyle = "green"; context.beginPath(); context.moveTo(0, 40); context.lineTo(80, 40); context.lineTo(40, 80); context.closePath(); context.stroke(); } // new point.x = x * cos(-angle) - y * sin(-angle), // new point.y = y * cos(-angle) + x * sin(-angle) function renderRotateText(context) { context.font="24px Arial"; context.fillStyle="red"; context.fillText("i'm here!!!",5,50); // rotate -90 degreee // context.rotate(-Math.PI/2); // context.fillStyle="blue"; // context.fillText("i'm here!!!", -400,30); // rotate 90 degreee context.rotate(Math.PI/2); context.fillStyle="blue"; context.fillText("i'm here!!!", 350,-420); console.log(Math.sin(Math.PI/2)); // rotae 90 degree and draw 10 lines context.fillStyle="green"; for(var i=0; i<4; i++) { var x = (i+1)*20; var y = (i+1)*60; var newX = y; var newY = -x; context.fillRect(newX, newY, 200, 6); } } function saveAndRestoreContext(context) { context.save(); context.translate(200,200); context.rotate(Math.PI/2); context.fillStyle="black"; context.fillText("2D Context Rotate And Translate", 10, 10); context.restore(); context.fillText("2D Context Rotate And Translate", 10, 10); } ~~~