调用imagemagick做响应图片

设计出图后经常需要改下尺寸放在别的项目上使用，每次都是设计手工处理，其实图片服务可以做更多事情，比如借助强大的im，可以通过url控制图片尺寸

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)
        })
    }

}

node前端是nginx 对处理过的图片就可以直接使用了

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;
    }
}