var childProcess = require('child_process')

 var path = require('path')

     ,http = require('http')

     ,fs = require('fs')

 const dns_host = 'xxx.net' //图片源站地址

 const PATH_IMGS = '/home/work/demo/images' //目录存放

 const PATH_IMG_TMP = '/home/work/demo/images' //临时目录

 //图片尺寸参数

 // /pic/_hd/cd/19/d6d821de10662d5352ff2d6bbaf2_960_420.cj.100x100x15.jpg

 const REG_RESIZE_OPT = /\.(\d+)?x(\d+[\!\>\<]?)?x(\d+)?\.jpg/

 //图片质量 默认85

 //  /pic/_hd/cd/19/d6d821de10662d5352ff2d6bbaf2_960_420.cj.q100.100x100x15.jpg

 const REG_QUALITY_OPT = /\.q(\d+)\.jpg/  //图片质量参数

 http.createServer(function(req, res) {

     var imgurl = req.url

         ,cdn_path = imgurl

     var options = cdn_path.match(REG_RESIZE_OPT )

     var img_suffix = path.extname(cdn_path)

     var opt_img = {}

     if (options){

         opt_img =

             {

             "width" : options[1] || ''

             ,"height" : options[2] || ''

             ,"mode" : options[3] | 0 || 1

             ,"imgurl" : imgurl

             }

         cdn_path = cdn_path.replace(REG_RESIZE_OPT, img_suffix)

     }

     options = cdn_path.match(REG_QUALITY_OPT)

     if (options) {

         opt_img.quality = options[1] | 0

         cdn_path = cdn_path.replace(REG_QUALITY_OPT, img_suffix)

     }

     opt_img.quality = opt_img.quality || 85

     if (opt_img.quality >= 100) delete opt_img.quality

     http.get('http://' + dns_host + cdn_path , function(response){

         //因为图片size变了 去掉content-length

         delete response.headers['content-length']

         res.writeHead(response.statusCode , response.headers)

         if (200 !== response.statusCode) return response.pipe(res)

         var file_tmp = path.resolve(PATH_IMG_TMP , 'tmp_' + (+new Date).toString(24) + (img_suffix || ''))

         //抓取远程图片 临时存图

         var writeStream = fs.createWriteStream(file_tmp)

         response.pipe(writeStream)

         writeStream.on('error' ,function(err){

             console.log('err' , err)

             res.end(err.toString())

         })

         response.on('end' ,function(err){

             imgWorker(file_tmp , opt_img , (err ,imgsrc) => {

                 if (err) return res.end(err.toString())

                 imgsrc = imgsrc || file_tmp

                 var read_stream = fs.createReadStream(imgsrc)

                 read_stream.pipe(res)

                 read_stream.on('end' ,function(){

                     fs.unlink(file_tmp)

                 })

             })

         })

     })

 }).listen(8791) //web服务端口

 function mkdirp(p){

     p = path.dirname(p)

     if (fs.existsSync(p)) return

     p = p.split('/')

     var pathnow = ''

     p.forEach(function(pi){

         pathnow += pi + '/'

         if (!fs.existsSync(pathnow) )  fs.mkdirSync(pathnow)

      })

 }

 function imgWorker( file_tmp ,opt ,cbk){

     opt = opt || {}

     const bindPath = '/usr/local/ImageMagick/bin/'

     var bindIdentity = bindPath + 'identify'

     /*

      * mode 0 等比

      * mode 1 剪切

      * mode 2 压缩填充

      * */

     if (!opt.height) opt.mode = 0

     convert()

     function convert(){

         var binConvert = bindPath + 'convert'

         var img_save_path = PATH_IMGS + opt.imgurl

         mkdirp(img_save_path)

         /*

         convert -resize 1024 file.jpg newfile.jpg

         得到图片宽为1024，高根据原始图片比例计算而来

         convert -resize x768 file.jpg newfile.jpg

         得到的图片高位768，宽根据原始图片比例计算而来

         convert -resize 1024×768! file.jpg newfile.jpg

         固定宽高缩放，不考虑原是图宽高的比例，把图片缩放到指定大小。

         convert -resize “1024×768>” file.jpg newfile.jpg

         只有当src.jpg的宽大于1024或高大于768时候，才进行缩小处理，否则生成newfile.jpg和file.jpg具有一样的尺寸。

         convert -resize “1024×768<” file.jpg newfile.jpg

         只有当src.jpg的宽小于1024或高小于768时候，才进行放大处理，否则生成newfile.jpg和file.jpg具有一样的尺寸。

         http://www.imagemagick.org/discourse-server/viewtopic.php?t=18545

         */

         var childArgs = []

         /*

          * NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast

          * NorthWest是左上角对齐 ，SouthEast是右下角对齐

          * 通过resize参数第二位可以控制对应对齐方式 默认Center 居中

          */

         if (opt.mode) {

             var _m = opt.mode.toString()

             var gravity = ['NorthWest', 'North', 'NorthEast', 'West'

                         , 'Center', 'East', 'SouthWest', 'South', 'SouthEast']

                             [(_m.slice(1,2) || 4) | 0]

             var color = ['' ,'white' ,'black'][(_m.slice(2,3) || 0) | 0]

             opt.mode = _m.slice(0,1) | 0

         }

         switch (opt.mode){

             case 2:

                 /*

                  * mode为2x 图片压缩填入指定尺寸 底色填充

                  * you can resize to the larger dimension and then pad the image

                  * convert image -resize "275x275" -gravity center -background white -extent 275x275 resultimage

                  */

                 childArgs.push('-resize')

                 childArgs.push(opt.width + 'x' + opt.height )

                 childArgs.push('-gravity')

                 childArgs.push(gravity)

                 if (color) {

                     childArgs.push('-background')

                     childArgs.push(color)

                 }

                 childArgs.push('-extent')

                 childArgs.push( opt.width + 'x' +  opt.height  )

                 break

             case 1:

                 /*

                 * mode为1x 图片拉伸 溢出剪切

                 */

                 var    cut = '+0+0'

                 childArgs.push('-resize')

                 childArgs.push(opt.width + 'x' + opt.height + '^')

                 childArgs.push('-gravity')

                 childArgs.push(gravity)

                 childArgs.push('-crop')

                 childArgs.push( opt.width + 'x' +  opt.height + cut )

                 break

             default:

                 /*

                 * 原图等比例缩放  比例不符合时以原图为准

                 */

                 var opt_size = opt.width || ''

                 if (opt.height) opt_size += 'x' + opt.height

                 if (opt_size){

                     childArgs.push('-resize')

                     childArgs.push(opt_size)

                 }

         }

         //去除元数据 相机信息 ps信息等

         childArgs.push('+profile')

         childArgs.push('"*"')

         childArgs.push('-strip')

         if (opt.quality){

             childArgs.push('-quality')

             childArgs.push(opt.quality)

         }

         childArgs.push(file_tmp)

         childArgs.push(img_save_path)

         console.log(childArgs)

         childProcess.execFile(binConvert, childArgs, function(err, stdout, stderr) {

             err && console.log(err)

             cbk(err  , img_save_path)

         })

     }

 }

 server {

     listen  80;

     server_name xxx.com;

     location /favicon.ico {

         return 418;

     }

     location / {

         root /home/work/demo/images ;

         try_files $uri $uri/  @router;

     }

     location @router {

         proxy_pass http://127.0.0.1:8791;

     }

 }