html5imagesupload

1. FileReader read images content
2. Get images naturalWidth naturalHeight
3. Create canvas for fill images
4. Resize canvas
5. Image to JPEGEncoder and send to servers

html5 大图片上传，自动缩放，可以选择多个文件，支持ios android 浏览器

html5 upload big pictures, auto scaling, you can select multiple files, supports ios Android browser