From e60eae758d032bbe03cfea615ef71bc066b416af Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Tue, 23 Aug 2011 12:49:45 -0400
Subject: [PATCH] Fix a JPEG parsing issue with Progressive DCT

---
 lib/image/jpeg.coffee | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/image/jpeg.coffee b/lib/image/jpeg.coffee
index 7cfbc1f..a21933c 100644
--- a/lib/image/jpeg.coffee
+++ b/lib/image/jpeg.coffee
@@ -9,14 +9,21 @@ class JPEG
     
     constructor: (@data) ->
         len = data.length
-        data.pos = 2 # Skip the first two bytes of JPEG identifier.
+        
+        if data.readUInt16() isnt 0xFFD8
+            throw "SOI not found in JPEG"
+        
+        markers = [0xFFC0, 0xFFC1, 0xFFC2, 0xFFC3, 0xFFC4, 0xFFC5, 0xFFC6, 0xFFC7,
+                   0xFFC8, 0xFFC9, 0xFFCA, 0xFFCB, 0xFFCC, 0xFFCD, 0xFFCE, 0xFFCF]
                 
         while data.pos < len
             marker = data.readUInt16()
-            break if marker is 0xFFC0
+            break if marker in markers
             data.pos += data.readUInt16()
         
-        data.pos += 2    
+        throw "Invalid JPEG." unless marker in markers
+        data.pos += 2
+         
         @bits = data.readByte()
         @height = data.readShort()
         @width = data.readShort()