主要思想：
使用canvas.toDataURL()将图片的绝对路径 转为 base64编码.
一、图片在本地服务器：
var imgSrc = "/img/1.jpg";//本地项目文件夹下的图片
function getBase64(img){//传入图片路径，返回base64
function getBase64Image(img,width,height) {
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.src = img;
var deferred=$.Deferred();
if(img){
image.onload =function (){
deferred.resolve(getBase64Image(image));//将base64传给done上传处理
}
return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
}
}
getBase64(imgSrc)
.then(function(base64){
console.log(base64);
},function(err){
console.log(err);
});
二、跨域
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>nick getBase64</title> </head> <body> <div><img id="test" src="" alt=""/></div> <script src="http://apps.bdimg.com/libs/jquery/2.1.1/jquery.min.js"></script> <script> var imgSrc = "https://img.alicdn.com/bao/uploaded/TB1qimQIpXXXXXbXFXXSutbFXXX.jpg"; // var imgSrc = "/img/1.jpg"; function getBase64(img){//传入图片路径，返回base64 function getBase64Image(img,width,height) {//width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小 var canvas = document.createElement("canvas"); canvas.width = width ? width : img.width; canvas.height = height ? height : img.height; var ctx = canvas.getContext("2d"); ctx.drawImage(img, 0, 0, canvas.width, canvas.height); var dataURL = canvas.toDataURL(); return dataURL; } var image = new Image(); image.crossOrigin = ''; image.src = img; var deferred=$.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); },function(err){ console.log(err); }); </script> </body> </html>
转载来自：https://www.cnblogs.com/LChenglong/p/7691548.html