无法在 HTMLCanvasElement 上执行 toDataURL

Question

从图像（本地文件）绘制画布后，我尝试使用命令导出它 ctx.canvas.toDataURL("image/png")

但是有一个错误：

DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.

我已经在谷歌搜索过了。他们说这是克罗斯的问题。所以，我添加了命令：

image.crossOrigin = '*';

但这对我的项目没用。实际上，我的项目是在没有任何服务器的情况下在本地构建的。所以，我不知道为什么会出现跨域问题。

function loadImageAsync(url) {
return new Promise(function(resolve, reject) {
    var image = new Image();
    image.onload = function() {
        image.crossOrigin = '*';
        resolve(image);
    };
    image.onerror = function() {
        reject(new Error('Could not load image at ' + url));
    };
    image.src = url;
});


  generate() {
    var p1 = loadImageAsync(this.textures[1]);
    var p2 = loadImageAsync(this.textures[2]);
    var p3 = loadImageAsync(this.textures[3]);
    var ctx = document.createElement("canvas")
        .getContext("2d");
    ctx.canvas.width = this.width;
    ctx.canvas.height = this.height;
    var rows = ~~(this.width / 70);
    var cols = ~~(this.height / 70);
    Promise.all([p1, p2, p3])
        .then(imgs => {
            for (let x = 0, i = 0; i < rows; x += 70, i++) {
                for (let y = 630, j = 0; j < cols; y -= 70, j++) {
                    this.resource[i].forEach(item => {
                        switch (item) {
                            case 1:
                                ctx.drawImage(imgs[0], x, y, 70, 70);
                                break;
                            case 2:
                                ctx.drawImage(imgs[1], x, y, 70, 70);
                                break;
                            case 3:
                                ctx.drawImage(imgs[2], x, y, 70, 70);
                                break;
                            default:
                        }
                    });
                }
            }
            //window.ctx = ctx;
            this.image.crossOrigin = '*';
            this.image.src = ctx.canvas.toDataURL("image/png");
        });
};

Answer 1

您需要crossOrigin在 onload 函数之外为图像设置。

return new Promise(function(resolve, reject) {
    var image = new Image();
    image.crossOrigin = '*';  //<-- set here
    image.onload = function() {
        resolve(image);
    };
    image.onerror = function() {
        reject(new Error('Could not load image at ' + url));
    };
    image.src = url;
});