From 8f25aa80b65d74955887685eafa2ae258e7cd700 Mon Sep 17 00:00:00 2001
From: cristy <urban-warrior@git.imagemagick.org>
Date: Sat, 23 Feb 2013 02:14:37 +0000
Subject: [PATCH]

---
 MagickCore/version.h |  2 +-
 coders/webp.c        | 58 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/MagickCore/version.h b/MagickCore/version.h
index 3b5d523d4..461e77c72 100644
--- a/MagickCore/version.h
+++ b/MagickCore/version.h
@@ -34,7 +34,7 @@ extern "C" {
 #define MagickLibAddendum  "-0"
 #define MagickLibInterface  1
 #define MagickLibMinInterface  1
-#define MagickReleaseDate  "2013-02-18"
+#define MagickReleaseDate  "2013-02-22"
 #define MagickChangeDate   "20121005"
 #define MagickAuthoritativeURL  "http://www.imagemagick.org"
 #define MagickFeatures "DPC HDRI OpenMP"
diff --git a/coders/webp.c b/coders/webp.c
index 398364dac..6f57eb239 100644
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -136,6 +136,62 @@ static MagickBooleanType IsWEBP(const unsigned char *magick,const size_t length)
 %    o exception: return any errors or warnings in this structure.
 %
 */
+
+static inline uint32_t get_le24(const unsigned char *const data)
+{
+  return((uint32_t) (data[0] | (data[1] << 8) | (data[2] << 16)));
+}
+
+static inline uint32_t get_le32(const unsigned char *const data)
+{
+  return((uint32_t) (get_le24(data) | (data[3] << 24)));
+}
+
+static MagickBooleanType IsWEBPImageLossless(const unsigned char *stream,
+  const size_t length)
+{
+#define VP8_CHUNK_INDEX  15  /* file/header type */
+#define LOSSLESS_FLAG  'L'
+#define EXTENDED_HEADER  'X'
+#define VP8_CHUNK_HEADER  "VP8"
+#define VP8_CHUNK_HEADER_SIZE  3
+#define RIFF_HEADER_SIZE  12  /* size of the RIFF header ("RIFFnnnnWEBP") */
+#define VP8X_CHUNK_SIZE  10
+#define TAG_SIZE  4
+#define CHUNK_SIZE_BYTES  4
+#define CHUNK_HEADER_SIZE  8
+#define MAX_CHUNK_PAYLOAD  (~0U-CHUNK_HEADER_SIZE-1)  /* header padding */
+
+  ssize_t
+    offset;
+
+  /*
+    Read simple header.
+  */
+  if (stream[VP8_CHUNK_INDEX] != EXTENDED_HEADER)
+   return(stream[VP8_CHUNK_INDEX] == LOSSLESS_FLAG ? MagickTrue : MagickFalse);
+  /*
+    Read extended header.
+  */
+  offset=RIFF_HEADER_SIZE+TAG_SIZE+CHUNK_SIZE_BYTES+VP8X_CHUNK_SIZE;
+  while (offset <= length)
+  {
+    uint32_t
+      chunk_size,
+      chunk_size_pad;
+
+    chunk_size=get_le32(stream+pos+TAG_SIZE);
+    if (chunk_size > MAX_CHUNK_PAYLOAD)
+      break;
+    chunk_size_pad=(CHUNK_HEADER_SIZE+chunk_size+1) & ~1;
+    if (memcmp( stream+offset,VP8_CHUNK_HEADER,VP8_CHUNK_HEADER_SIZE) == 0)
+      return*(stream+offset+VP8_CHUNK_HEADER_SIZE) == LOSSLESS_FLAG ?
+        MagickTrue : MagickFalse);
+    offset+=chunk_size_pad;
+  }
+  return(MagickFalse);
+}
+
 static Image *ReadWEBPImage(const ImageInfo *image_info,
   ExceptionInfo *exception)
 {
@@ -208,7 +264,7 @@ static Image *ReadWEBPImage(const ImageInfo *image_info,
   image->rows=(size_t) webp_image->height;
   image->alpha_trait=features->has_alpha != 0 ? BlendPixelTrait :
     UndefinedPixelTrait;
-  if (stream[15] == 'L')
+  if (IsWEBPImageLossless(stream,length) != MagickFalse)
     image->quality=100;
   p=webp_image->u.RGBA.rgba;
   for (y=0; y < (ssize_t) image->rows; y++)
-- 
2.40.0