diff --git a/app.js b/app.js
index 91d8145..60b3c41 100644
--- a/app.js
+++ b/app.js
@@ -462,91 +462,70 @@ app.post('/uploadimage', function (req, res) {
         form.uploadDir = "public/uploads";
     }
 
-    function preprocessImage(path) {
-        return new Promise((resolve) => {
-            var oldFile = `${path}-old`;
-            fs.rename(path, oldFile, function() {
-                var sharp = require('sharp');
-                sharp(oldFile).toFile(path).then(() => {
-                    fs.unlink(oldFile, function() {
-                        resolve(path);
-                    })
-                });
-            });
-        });
-    }
-
     form.parse(req, function (err, fields, files) {
         if (err || !files.image || !files.image.path) {
             response.errorForbidden(res);
         } else {
-            preprocessImage(files.image.path).then(() => {
-                if (config.debug)
-                    logger.info('SERVER received uploadimage: ' + JSON.stringify(files.image));
+            if (config.debug)
+                logger.info('SERVER received uploadimage: ' + JSON.stringify(files.image));
+                
+            try {
+                switch (config.imageUploadType) {
+                case 'filesystem':
+                    res.send({
+                        link: path.join(config.serverurl, files.image.path.match(/^public(.+$)/)[1])
+                    });
 
-                var path = require('path');
-                try {
-                    switch (config.imageUploadType) {
-                    case 'filesystem':
-                        res.send({
-                            link: path.join(config.serverurl, files.image.path.match(/^public(.+$)/)[1])
-                        });
+                    break;
 
-                        break;
+                case 's3':
+                    var AWS = require('aws-sdk');
+                    var awsConfig = new AWS.Config(config.s3);
+                    var s3 = new AWS.S3(awsConfig);
 
-                    case 's3':
-                        var AWS = require('aws-sdk');
-                        var awsConfig = new AWS.Config(config.s3);
-                        var s3 = new AWS.S3(awsConfig);
+                    fs.readFile(files.image.path, function (err, buffer) {
+                        var params = {
+                            Bucket: 'hackmd',
+                            Key: path.join('uploads', path.basename(files.image.path)),
+                            Body: buffer
+                        };
 
-                        fs.readFile(files.image.path, function (err, buffer) {
-                            var params = {
-                                Bucket: 'hackmd',
-                                Key: path.join('uploads', path.basename(files.image.path)),
-                                Body: buffer
-                            };
-
-                            s3.putObject(params, function (err, data) {
-                                if (err) {
-                                    logger.error(err);
-                                    res.status(500).end('upload image error');
-                                } else {
-                                    res.send({
-                                        link: `https://s3-${config.s3.region}.amazonaws.com/${config.s3bucket}/${params.Key}`
-                                    });
-                                }
-                            });
-
-                        });
-
-                        break;
-
-                    case 'imgur':
-                    default:
-                        imgur.setClientId(config.imgur.clientID);
-                        imgur.uploadFile(files.image.path)
-                            .then(function (json) {
-                                if (config.debug)
-                                    logger.info('SERVER uploadimage success: ' + JSON.stringify(json));
-                                res.send({
-                                    link: json.data.link.replace(/^http:\/\//i, 'https://')
-                                });
-                            })
-                            .catch(function (err) {
+                        s3.putObject(params, function (err, data) {
+                            if (err) {
                                 logger.error(err);
-                                return res.status(500).end('upload image error');
-                            });
-                        break;
-                    }
-                } catch (err) {
-                    logger.error(err);
-                    return res.status(500).end('upload image error');
-                }
+                                res.status(500).end('upload image error');
+                            } else {
+                                res.send({
+                                    link: `https://s3-${config.s3.region}.amazonaws.com/${config.s3bucket}/${params.Key}`
+                                });
+                            }
+                        });
 
-            }).catch((err) => {
+                    });
+
+                    break;
+
+                case 'imgur':
+                default:
+                    imgur.setClientId(config.imgur.clientID);
+                    imgur.uploadFile(files.image.path)
+                        .then(function (json) {
+                            if (config.debug)
+                                logger.info('SERVER uploadimage success: ' + JSON.stringify(json));
+                            res.send({
+                                link: json.data.link.replace(/^http:\/\//i, 'https://')
+                            });
+                        })
+                        .catch(function (err) {
+                            logger.error(err);
+                            return res.status(500).end('upload image error');
+                        });
+                    break;
+                }
+            } catch (err) {
                 logger.error(err);
-                return res.status(500).end('process image error');
-            });
+                return res.status(500).end('upload image error');
+            }
         }
     });
 });
diff --git a/package.json b/package.json
index e6bd2c5..c3b71f1 100644
--- a/package.json
+++ b/package.json
@@ -101,7 +101,6 @@
     "scrypt": "^6.0.3",
     "select2": "^3.5.2-browserify",
     "sequelize-cli": "^2.4.0",
-    "sharp": "^0.16.2",
     "shortid": "2.2.6",
     "socket.io": "~1.6.0",
     "socket.io-client": "~1.6.0",