js 压缩图片 H5

/*common*/var canvasSupported = isCanvasSupported()function dataURItoBlob(dataURI) {
// convert base64 to raw binary data held in a string
var byteString
,mimestring if(dataURI.split(',')[].indexOf('base64') !== - ) {
byteString = atob(dataURI.split(',')[])
} else {
byteString = decodeURI(dataURI.split(',')[])
} mimestring = dataURI.split(',')[].split(':')[].split(';')[] var content = new Array();
for (var i = ; i < byteString.length; i++) {
content[i] = byteString.charCodeAt(i)
} return new Blob([new Uint8Array(content)], {type: mimestring});
}function imgScale (src , scale,cbk) {
if (!src) return cbk(false)
var _canvas = document.createElement('canvas')
var tImg = new Image
tImg.onload = function(){
var _context = _canvas.getContext('2d');
_context.drawImage(tImg,,);
var type = 'image/jpeg'
src = _canvas.toDataURL(type , scale)
var blob = dataURItoBlob(src)
cbk(blob)
/*
var r = _canvas.mozGetAsFile('f' , type)
cbk(r)
*/
};
tImg.src = src}function isCanvasSupported(){
var elem = document.createElement('canvas');
return !!(elem.getContext && elem.getContext('2d'));
}exports.support = canvasSupported /* opt {scale :0-1}*/
exports.zip = function(files ,opt,cbk){
opt = opt || {}
var scale = opt.scale
if (!canvasSupported) return cbk(files)
if (!scale || == scale ) return cbk(files)
var files_count = files.length
,ret = [] for (var i = ,j = files.length ; i<j ; i++){
var fReader = new FileReader();
fReader.onload = function (e){
var result = e.target.result
imgScale(result , scale ,function(file){
file && ret.push(file)
files_count--
if (files_count <= ) cbk && cbk(ret) })
};
fReader.readAsDataURL(files[i]);
}
}

var compress = require('app/compress')if (compress.support){
compress.zip(files , {'scale':opt.compress} , function(files){
console.log(files)
//返回的 blob 对象可以 append 到 FormData对象上 用 ajax 上传
})
}