钉钉h5环境，ios长按图片查看大图失败？

将图片src转换成base64即可

    const imgDom = document.querySelector("#picture");
    let img = new Image();
    img.src = imgDom.src;
    img.onload = function() {
        let canvas = document.createElement('canvas');
        canvas.width = img.width;
        canvas.height = img.height;
        let ctx = canvas.getContext('2d');
        ctx.drawImage(img, 0, 0, img.width, img.height);
        picture.src = canvas.toDataURL('img/jpeg')

    }