使用javascript将图像转换为base64

Question

function convertImgToBase64(url){ 

    var canvas = document.createElement('CANVAS'); 
    var ctx = canvas.getContext('2d'); 
    var img = new Image; 
    img.crossOrigin = 'Anonymous'; 
    img.onload = function(){ 
    canvas.height = img.height; 
    canvas.width = img.width; 
     ctx.drawImage(img,0,0); 
     var dataURL = canvas.toDataURL('image/png',""); 
     alert(dataURL); 

     canvas = null; 
    }; 
    img.src = url; 



} 

var url_to_be_converted = "http://www.google.com/image/sample" 
convertImgToBase64(url_to_be_converted); 

Alert（dataURL）不显示任何结果。是否在此处生成弹出窗口？如何解决这个问题？
有什么不对？

Answer 1

有一个跨源问题...尝试使用此功能

function convertImgToBase64(url) 
{ 
    var canvas = document.createElement('CANVAS'); 
    img = document.createElement('img'), 
    img.src = url; 
    img.onload = function() 
    { 
     canvas.height = img.height; 
     canvas.width = img.width; 
     var dataURL = canvas.toDataURL('image/png'); 
     alert(dataURL); 
     canvas = null; 
    }; 
} 

我删除的背景和我以不同的方式