js 图片转换为base64 (2)

// 前端只需要给input file绑定这个change事件即可（下面两个方法不需要修改）获取到图片

$('#testUpload').change(function(event){

var imageUrl = getObjectURL($(this)[0].files[0]);

//imageUrl = staticpath+"/images/businessLicensePath_1511499859533.png";

convertImgToBase64(imageUrl, function(base64Img){

$("#img").attr("src",base64Img);

console.log(base64Img);

//base64Img为转好的base64,放在img src直接前台展示(<img src="data:image/jpg;base64,/9j/4QMZRXh...." />)

//alert(base64Img);

$("#base").attr("src",base64Img);

//base64转图片不需要base64的前缀data:image/jpg;base64

//alert(base64Img.split(",")[1]);

$("#uploadFile").val(base64Img.split(",")[1]);

});

event.preventDefault();

});

//生成图片的base64编码

function convertImgToBase64(url, callback, outputFormat){

//html5 的convas画布

var canvas = document.createElement('CANVAS');

var ctx = canvas.getContext('2d');

var img = new Image;

img.crossOrigin = 'Anonymous';

img.onload = function(){

var width = img.width;

var height = img.height;

// 按比例压缩4倍

//var rate = (width<height ? width/height : height/width)/4;

//原比例生成画布图片

var rate = 1;

canvas.width = width*rate;

canvas.height = height*rate;

ctx.drawImage(img,0,0,width,height,0,0,width*rate,height*rate);

// canvas.toDataURL 返回的是一串Base64编码的URL，当然,浏览器自己肯定支持

var dataURL = canvas.toDataURL(outputFormat || 'image/png');

callback.call(this, dataURL);

canvas = null;

};

img.src = url;

}

//createobjecturl()静态方法创建一个包含了DOMString代表参数对象的URL。该url的声明周期是在该窗口中.也就是说创建浏览器创建了一个代表该图片的Url.

function getObjectURL(file) {

var url = null ;

if (window.createObjectURL!=undefined){

// basic

url = window.createObjectURL(file) ;

} else if (window.URL!=undefined){

// mozilla(firefox)

url = window.URL.createObjectURL(file) ;

} else if (window.webkitURL!=undefined){

//web_kit or chrome

url = window.webkitURL.createObjectURL(file) ;

}

return url ;

}

</script>