画布剪辑图像在一个圆圈 [英] canvas clip image in a circle

问题描述

我只是想在曲线中剪辑图片..但是没有发生这种情况..
只有图片显示但没有剪辑。

I just wanted to clip image in a curve .. but not happening this.. Only image is showing and but not with clip.

HTML

<canvas id="leaf" width="500" height="500" style='left: 0; 
position: absolute; top: 0;'></canvas>

JavaScript

var canvas = document.getElementById('leaf');
var context = canvas.getContext('2d');

/*
* save() allows us to save the canvas context before
* defining the clipping region so that we can return
* to the default state later on
*/

context.save();
context.beginPath();
context.moveTo(188, 150);
context.quadraticCurveTo(288, 0, 388, 150);
context.lineWidth = 10;
context.quadraticCurveTo(288, 288, 188, 150);
context.lineWidth = 10;

context.clip();

context.beginPath();
var imageObj = new Image();
imageObj.onload = function()
{
context.drawImage(imageObj, 10, 50);
};

imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg';

/* context.beginPath();
context.arc(x - offset, y - offset, radius, 0, 2 * Math.PI, false);
context.fillStyle = 'yello';
context.fill();
*/

/*
* restore() restores the canvas context to its original state
* before we defined the clipping region
*/

context.restore();
context.beginPath();
context.moveTo(188, 150);
context.quadraticCurveTo(288, 0, 388, 150);
context.lineWidth = 10;
context.quadraticCurveTo(288, 288, 188, 150);
context.lineWidth = 10;

context.strokeStyle = 'blue';
context.stroke();

推荐答案

你必须从<$ c行移动一切$ c> context.save（）; 到 context.clip（）; 在 imgObj <的函数对象内/ code>的 onload 处理程序：

You have to move everything from the line context.save(); to context.clip(); inside the function object of your imgObj's onload handler:

imageObj.onload = function()
{
    context.save();
    context.beginPath();
    context.moveTo(188, 150);
    context.quadraticCurveTo(288, 0, 388, 150);
    context.lineWidth = 10;
    context.quadraticCurveTo(288, 288, 188, 150);
    context.lineWidth = 10;
    context.clip();
    context.drawImage(imageObj, 10, 50);
};

参见 http://jsfiddle.net/CSkP6/1/ 的例子。

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