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我试图裁掉透明度,但我找不到怎样的方法.
这可以通过将png加载到HTML-5 canvas元素中,然后在画布中查询所单击像素的alpha值来实现.
工作演示:http://jsfiddle.net/x9ScK/3/
HTML如下……
<!-- create a canvas element to hold the PNG image --> <canvas id="canvas1" width="500" height="500"></canvas>
像这样的Javascript ……
// select the canvas element with jQuery,and set up // a click handler for the whole canvas $('#canvas1').on('click',function(e) { // utility function for finding the position of the clicked pixel function findPos(obj) { var curleft = 0,curtop = 0; if (obj.offsetParent) { do { curleft += obj.offsetLeft; curtop += obj.offsetTop; } while (obj = obj.offsetParent); return { x: curleft,y: curtop }; } return undefined; } // get the position of clicked pixel var pos = findPos(this); var x = e.pageX - pos.x; var y = e.pageY - pos.y; // get reference to canvas element clicked on var canvas = this.getContext('2d'); // return array of [RED,GREEN,BLUE,ALPHA] as 0-255 of clicked pixel var pixel = canvas.getImageData(x,y,1,1).data; // if the alpha is not 0,we clicked a non-transparent pixel // could be easily adjusted to detect other features of the clicked pixel if(pixel[3] != 0){ // do something when clicking on image... alert("Clicked the dice!"); } }); // get reference to canvas DOM element var canvas = $('#canvas1')[0]; // get reference to canvas context var context = canvas.getContext('2d'); // create an empty image var img = new Image(); // after loading... img.onload = function() { // draw the image onto the canvas context.drawImage(img,0); } // set the image source (can be any url - I used data URI to keep demo self contained) img.src = "data:image/png;base64,iVBORw0KGgoAAAANS ... more image data ...TkSuQmCC"; // PNG with transparency
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