请教各位大神，本人有个项目在小程序中运行h5页面，需要使用h5进行图片压缩，目前大量用户遇到了安卓上压缩后的图片是黑图（设置底色为白色），ios上传的是白图，部分oppo手机的图片为上半张图正常，下半张图类似绿色蒙层，源码如下：

let canvas = document.createElement("canvas");

let ctx = canvas.getContext('2d');

let initSize = img.src.length;

let width = img.width;

let height = img.height;

//如果图片大于四百万像素，计算压缩比并将大小压至400万以下

let ratio;

if ((ratio = width * height / 4000000) > 1) {

ratio = Math.sqrt(ratio);

width /= ratio;

height /= ratio;

} else {

ratio = 1;

}

canvas.width = width;

canvas.height = height;

//        铺底色

ctx.fillStyle = "#fff";

ctx.fillRect(0, 0, canvas.width, canvas.height);

//如果图片像素大于100万则使用瓦片绘制

let count;

if ((count = width * height / 1000000) > 1 && Util.isIOS()) {

count = Math.ceil(Math.sqrt(count)); //计算要分成多少块瓦片

//            计算每块瓦片的宽和高

var nw = ~~(width / count);

var nh = ~~(height / count);

//    瓦片canvas

for (var i = 0; i < count; i++) {

for (var j = 0; j < count; j++) {

let tCanvas = document.createElement("canvas");

let tCtx = tCanvas.getContext("2d");

tCanvas.width = nw;

tCanvas.height = nh;

tCtx.drawImage(img, Math.ceil(i * nw * ratio), Math.ceil(j * nh * ratio), Math.ceil(nw * ratio), Math.ceil(nh * ratio), 0, 0, nw, nh);

ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);

}

}

} else {

ctx.drawImage(img, 0, 0, width, height);

}

let data = canvas.toDataURL('image/jpeg', 0.7);

跪谢各位大神，急急急！！！