记录 javascript canvas ImageData 解析

数组的内容: 　　data.length: w * h * 4 　　r: 0 - 255 　　g: 0 - 255 　　b: 0 - 255 　　a: 0 - 255 Math.round(255 * a)   数组遍历:

const data = context.getImageData(0, 0, canvas.width, canvas.height).data,
len = canvas.width * canvas.height;

for(let k = 0, x, y, r, g, b, a, i; k < len; k++){
    x = k % width;
    y = Math.floor(k / width);

    i = k*4;
    r = data[i]
    g = data[i+1]
    b = data[i+2]
    a = data[i+3]

    console.log(x, y, r, g, b, a, i);
}