我需要获取画布中透明/不透明像素的比例。做这个的最好方式是什么?HTML5获取画布中alpha像素的数量
UPDATE: 基于下面的帖子中,我结束了写这个代码:
function getNumberOfAlphaPixels(can) {
var step = 200; //We skip 200 pixels to make it work faster
var ctx = can.getContext('2d');
var imgd = ctx.getImageData(0, 0, can.width, can.height);
var pix = imgd.data;
var alphaPixelsNum = 0;
for (var i = 0; i < pix.length; i += 4*step) {
if (pix[i+3] == 0) {
alphaPixelsNum += step;
}
}
return alphaPixelsNum;
}
这比我的伪代码快。最后一行是否指'alphaPixels'? – paislee 2012-02-01 19:07:43
@paislee - 是的,谢谢你发现 – andrewmu 2012-02-01 20:17:17