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介绍
HTML 5: 画布(canvas)之转换(转换画布的用户坐标系)
平移 | translate()
旋转 | rotate()
缩放 | scale()
矩阵转换 | transform(a, b, c, d, e, f)
矩阵转换 | setTransform(a, b, c, d, e, f)
示例
1、平移 | translate()
canvas/transform/translate.html
平移
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不断地点我看 Demo
清除画布
var ctx = document.getElementById('canvas').getContext('2d');
var canvasX = 0;
var canvasY = 0;
var stepX = 20;
var stepY = 20;
function drawIt() {
if (canvasX == 0 && canvasY == 0)
ctx.strokeRect(0, 0, 100, 100);
canvasX += stepX;
canvasY += stepY;
/*
* context.translate(x, y) - 将当前的用户坐标系平移指定的距离
* x - x 轴方向上需要平移的像素数
* y - y 轴方向上需要平移的像素数
*/
ctx.strokeStyle = "blue";
ctx.translate(stepX, stepY);
ctx.strokeRect(0, 0, 100, 100);
}
function clearIt() {
ctx.translate(-canvasX, -canvasY);
canvasX = 0;
canvasY = 0;
ctx.strokeStyle = "black";
ctx.clearRect(0, 0, 400, 400);
}
2、旋转 | rotate()
canvas/transform/rotate.html
旋转
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不断地点我看 Demo
清除画布
var ctx = document.getElementById('canvas').getContext('2d');
var canvasRadian = 0;
var stepRadian = 15 * Math.PI / 180;
function drawIt() {
if (canvasRadian == 0)
ctx.strokeRect(360, 0, 20, 60);
canvasRadian += stepRadian;
/*
* context.rotate(radian) - 将当前的用户坐标系旋转指定的弧度,顺时针为正值,逆时针为负值
* radian - 弧度值
*/
ctx.strokeStyle = "blue";
ctx.rotate(stepRadian);
ctx.strokeRect(360, 0, 20, 60);
}
function clearIt() {
ctx.rotate(-canvasRadian);
canvasRadian = 0;
ctx.strokeStyle = "black";
ctx.clearRect(0, 0, 400, 400);
}
3、缩放 | scale()
canvas/transform/scale.html
缩放
您的浏览器不支持 canvas 标签
不断地点我看 Demo
清除画布
var ctx = document.getElementById('canvas').getContext('2d');
var canvasScaleX = 1;
var canvasScaleY = 1;
var stepScaleX = 1.1;
var stepScaleY = 1.1;
function drawIt() {
if (canvasScaleX == 1 && canvasScaleY == 1)
ctx.strokeRect(0, 0, 60, 60);
canvasScaleX *= stepScaleX;
canvasScaleY *= stepScaleY;
/*
* context.scale(x, y) - 将当前的用户坐标系缩放指定的倍数
* x - 水平方向上的缩放倍数
* y - 垂直方向上的缩放倍数
*/
ctx.strokeStyle = "blue";
ctx.scale(stepScaleX, stepScaleY);
ctx.strokeRect(0, 0, 60, 60);
}
function clearIt() {
ctx.scale(1 / canvasScaleX, 1 / canvasScaleY);
canvasScaleX = 1;
canvasScaleY = 1;
ctx.strokeStyle = "black";
ctx.clearRect(0, 0, 400, 400);
}
4、矩阵转换 | transform(a, b, c, d, e, f)
canvas/transform/transform.html
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