From 135e8b1942e1e9e226422ea37f6c72db9e26674f Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Thu, 16 Feb 2012 17:41:29 -0800
Subject: [PATCH] WebPMuxGetImage: allow image param to be NULL

but not both alpha & image

Change-Id: I6822a740de7577eedcbe7529382aa2c020d1e8e4
---
 src/mux/muxread.c | 13 ++++++++-----
 src/webp/mux.h    |  4 ++--
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/mux/muxread.c b/src/mux/muxread.c
index 1cefbc69..9c605840 100644
--- a/src/mux/muxread.c
+++ b/src/mux/muxread.c
@@ -230,8 +230,8 @@ WebPMuxError WebPMuxGetImage(const WebPMux* const mux,
   WebPMuxError err;
   WebPMuxImage* wpi = NULL;
 
-  if (mux == NULL || image == NULL) return WEBP_MUX_INVALID_ARGUMENT;
-  memset(image, 0, sizeof(*image));
+  if (mux == NULL || (image == NULL && alpha == NULL))
+    return WEBP_MUX_INVALID_ARGUMENT;
 
   err = ValidateForImage(mux);
   if (err != WEBP_MUX_OK) return err;
@@ -250,9 +250,12 @@ WebPMuxError WebPMuxGetImage(const WebPMux* const mux,
   }
 
   // Get image chunk.
-  if (wpi->vp8_ != NULL) {
-    image->bytes_ = wpi->vp8_->data_;
-    image->size_ = wpi->vp8_->payload_size_;
+  if (image != NULL) {
+    memset(image, 0, sizeof(*image));
+    if (wpi->vp8_ != NULL) {
+      image->bytes_ = wpi->vp8_->data_;
+      image->size_ = wpi->vp8_->payload_size_;
+    }
   }
   return WEBP_MUX_OK;
 }
diff --git a/src/webp/mux.h b/src/webp/mux.h
index e74c1479..138f54db 100644
--- a/src/webp/mux.h
+++ b/src/webp/mux.h
@@ -148,8 +148,8 @@ WEBP_EXTERN(WebPMuxError) WebPMuxSetImage(WebPMux* const mux,
 //   image - (out) the image data
 //   alpha - (out) the alpha data of the image (if present)
 // Returns:
-//   WEBP_MUX_INVALID_ARGUMENT - if either mux or image is NULL
-//                               OR if mux contains animation/tiling.
+//   WEBP_MUX_INVALID_ARGUMENT - if either mux or both image & alpha are NULL
+//                               OR mux contains animation/tiling.
 //   WEBP_MUX_NOT_FOUND - if image is not present in mux object.
 //   WEBP_MUX_OK - on success.
 WEBP_EXTERN(WebPMuxError) WebPMuxGetImage(const WebPMux* const mux,