HTML5 Canvas压缩图片 AJAX上传图片

Canvas压缩图片

封装压缩图片的js

function compress(event,callback){
    //var inputID="file";
    var file = event.files[0];  
    var reader = new FileReader();
    reader.onload = function (e) {
        var image = $('<img />');
        image.on('load',function () {
            var canvas = document.createElement('canvas');
            var width = this.width;
            var height = this.height;

            canvas.width = this.width;
            canvas.height = this.height;

            var context = canvas.getContext('2d');
            context.clearRect(0,0,width,height);

            context.drawImage(this,this.width,this.height);
            var quality = 0.9;//可以理解为压缩程度
            //quality :图片质量。0 到 1 之间的数字，并且只在格式为 image/jpeg 或 image/webp 时才有效，如果参数值格式不合法，将会被忽略并使用默认值
            var data ;
            var result;
            var length;
            //处理图片过大问题
            //控制图片上传的大小，注意若图片过大 ajax上传的时候会出现参数为null的错误
            //这里如果图片过大会将图片压缩程度放大
            do{
                data= canvas.toDataURL('image/jpeg',quality);//压缩图片
                length = data.length;
                result = ((length/4)*3+1023)/1024;//计算压缩后图片的大小（单位：KB）
                console.log("result:"+result);
                quality-=0.05;
            }while(result>450);
            //data：base64
            callback(data);//回调函数
         });
          image.attr('src',e.target.result);
       };
     reader.readAsDataURL(file);
}

调用compress方法获取base64图片编码并使用AJAX上传

compress($("#imgID"),function(base64Img){
    $.ajax({
        type:"POST",url:$("#basePath").val()+"material/uploadMaterial",data:{
            base64Img : base64Img
        },success:function(data){
            var result = eval('(' + data + ')');
             if(result =='SUC'){
                 alert("上传成功");
                 return false;
             }else{
                 alert("上传失败，请稍后重试");
                 return false;
             }
        }
    });
});

UploadController.java

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.util.UUID;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import sun.misc.BASE64Decoder;

@Controller
@RequestMapping(value="/upload")
public class UploadController {

    private static final Logger logger = Logger.getLogger(UploadController.class);

    @ResponseBody
    @RequestMapping("/uploadImg")
    public synchronized String uploadImg(String base64Img,HttpServletRequest request,HttpServletResponse response) 
                    throws IllegalStateException,IOException{
        logger.info("uploadMaterial#####图片...");
        String imgName;
        String imgPath;
        imgName=UUID.randomUUID().toString().replace("-","")+".jpeg";//生成名字
        imgPath="/app/mount/imageServer/material/"+imgName;//上传路径
        String[]  strs=base64Img.split(",");
        //System.out.println("base64:"+strs[1]);
        try {
            String data =savePictoServer(strs[1],imgPath);
            logger.info("--->>>图片上传成功!::"+data);
            return "SUC";
        } catch (Exception e) {
            logger.info("uploadMaterial######图片转化异常......");
            return "图片上传失败，请稍后重试";
        }
    }

    //图片上传
    public static String savePictoServer(String base64String,String path)throws Exception{
          BASE64Decoder decoder = new sun.misc.BASE64Decoder(); 
                byte[] bytes1 = decoder.decodeBuffer(base64String); 
                ByteArrayInputStream bais = new ByteArrayInputStream(bytes1); 
                BufferedImage bi1 =ImageIO.read(bais); 

                File dir=new File(path);
                if(!dir.exists()){
                 dir.mkdirs();
                }
                String fileName=path;
                File w2 = new File(fileName);//可以是jpg,png,gif格式 
                ImageIO.write(bi1,"jpg",w2);//不管输出什么格式图片，此处不需改动 
                return fileName;
    }
}

使用到的jar包

catalina-manager.jar、commons-fileupload-1.2.1.jar、commons-io-1.3.2.jar