通过Javascript获取图像的平均颜色

AFAIK，做到这一点的唯一方法是

<canvas/>

请注意，这仅适用于相同域中的图像以及支持HTML5 canvas的浏览器：

function getAverageRGB(imgEl) {    var blockSize = 5, // only visit every 5 pixels        defaultRGB = {r:0,g:0,b:0}, // for non-supporting envs        canvas = document.createElement('canvas'),        context = canvas.getContext && canvas.getContext('2d'),        data, width, height,        i = -4,        length,        rgb = {r:0,g:0,b:0},        count = 0;    if (!context) {        return defaultRGB;    }    height = canvas.height = imgEl.naturalHeight || imgEl.offsetHeight || imgEl.height;    width = canvas.width = imgEl.naturalWidth || imgEl.offsetWidth || imgEl.width;    context.drawImage(imgEl, 0, 0);    try {        data = context.getImageData(0, 0, width, height);    } catch(e) {                return defaultRGB;    }    length = data.data.length;    while ( (i += blockSize * 4) < length ) {        ++count;        rgb.r += data.data[i];        rgb.g += data.data[i+1];        rgb.b += data.data[i+2];    }    // ~~ used to floor values    rgb.r = ~~(rgb.r/count);    rgb.g = ~~(rgb.g/count);    rgb.b = ~~(rgb.b/count);    return rgb;}