Only hijack the response if the url specifies an image extension acco…

…rding to the mime lib.

lib/processImage.js

@@ -1,15 +1,31 @@
 var Path = require('path'),
-    getFilterInfosAndTargetContentTypeFromQueryString = require('./getFilterInfosAndTargetContentTypeFromQueryString');
+    getFilterInfosAndTargetContentTypeFromQueryString = require('./getFilterInfosAndTargetContentTypeFromQueryString'),
+    mime = require('mime');
 
 require('express-hijackresponse');
 
+var isImageByExtension = {};
+
+Object.keys(mime.extensions).forEach(function (contentType) {
+    if (/^image\//.test(contentType)) {
+        var extension = mime.extensions[contentType];
+        isImageByExtension[extension] = true;
+    }
+});
+
+isImageByExtension.jpg = true;
+
+function isImageExtension(extension) {
+    return isImageByExtension[extension.toLowerCase()];
+}
+
 module.exports = function (options) {
     options = options || {};
     return function (req, res, next) {
-        var matchQueryString = req.url.match(/\?(.*)$/);
-        if (matchQueryString && req.accepts('image/*')) {
+        var matchExtensionAndQueryString = req.url.match(/\.(\w+)\?(.*)$/);
+        if (matchExtensionAndQueryString && isImageExtension(matchExtensionAndQueryString[1]) && req.accepts('image/*')) {
             // Prevent If-None-Match revalidation with the downstream middleware with ETags that aren't suffixed with "-processimage":
-            var queryString = matchQueryString[1],
+            var queryString = matchExtensionAndQueryString[2],
                 ifNoneMatch = req.headers['if-none-match'];
             if (ifNoneMatch) {
                 var validIfNoneMatchTokens = ifNoneMatch.split(' ').filter(function (etag) {

package.json

@@ -12,6 +12,7 @@
     "gm": "1.6.1",
     "inkscape": "0.0.5",
     "jpegtran": "0.0.6",
+    "mime": "1.2.11",
     "optimist": "0.6.1",
     "optipng": "0.1.1",
     "passerror": "0.0.1",