image 跨域问题

 

重点是：img.crossOrigin = "Anonymous"

 

function cacheExternalImage(url){
    var img = new Image,
    src = url,
    cvs = document.createElement('canvas'),
    ctx = cvs.getContext('2d');
    img.crossOrigin = "Anonymous";
    img.onload = function() {
      //ctx.drawImage( img, 0, 0 );
    }
    img.src = src;
    if ( img.complete || img.complete === undefined ) {
        img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
        img.src = src;
    }
    return img;
}

 

 

参考：https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image

http://www.web-tinker.com/article/20687.html