[英]canvas clip image in a circle
我只是想在曲線中剪輯圖像..但是沒有發生這種情況..只有圖像顯示,但不是剪輯。
HTML
<canvas id="leaf" width="500" height="500" style='left: 0;
position: absolute; top: 0;'></canvas>
JavaScript的
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();
你必須從行context.save();
to context.clip();
在imgObj
的onload
處理程序的函數對象中:
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);
};
有關示例,請參見http://jsfiddle.net/CSkP6/1/ 。
在腳本啟動幾次之后,當您的圖像被加載時,您不再需要剪切的畫布,因為您之后會恢復它。
你需要做一個drawClipped函數,並在你的onload函數中調用它,例如:
function drawClipped(context, myImage) = {
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(myImage, 10, 50);
context.restore();
};
var imageObj = new Image();
imageObj.onload = function() {
drawClipped(context, imageObj);
};
imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg';
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