根据图片的路径（绝对路径/相对路径都可以），生成base64的
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>nick getBase64</title> </head> <body> <div><img id="test" src="" alt=""/></div> <script src="jquery.min.js"></script> <script> // var imgSrc = "https://img.alicdn.com/bao/uploaded/TB1qimQIpXXXXXbXFXXSutbFXXX.jpg"; var imgSrc = "pic.jpg"; // var imgSrc = "img/1.jpg"; function getBase64(img){//传入图片路径，返回base64 function getBase64Image(img,width,height) {//width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小 var canvas = document.createElement("canvas"); canvas.width = width ? width : img.width; canvas.height = height ? height : img.height; var ctx = canvas.getContext("2d"); ctx.drawImage(img, 0, 0, canvas.width, canvas.height); var dataURL = canvas.toDataURL(); return dataURL; } var image = new Image(); image.crossOrigin = ''; image.src = img; var deferred=$.Deferred(); if(img){ image.onload =function (){ deferred.resolve(getBase64Image(image));//将base64传给done上传处理 } return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest'] } } getBase64(imgSrc) .then(function(base64){ console.log(base64); $("#test").attr("src",base64) },function(err){ console.log(err); }); </script> </body> </html>