From 2914ecfd560f615120685e5d151dd0628d34b7b2 Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Sat, 15 Dec 2012 19:41:03 -0800
Subject: [PATCH] cwebp/tiffdec: add TIFF metadata extraction

currently the values of XMP/ICC are unused and EXIF is ignored.

Change-Id: I1d8b73bde4db2768f117158f986aadbaaec45804
---
 examples/cwebp.c   |  2 +-
 examples/tiffdec.c | 62 +++++++++++++++++++++++++++++++++++++++++++---
 examples/tiffdec.h |  4 ++-
 3 files changed, 62 insertions(+), 6 deletions(-)

diff --git a/examples/cwebp.c b/examples/cwebp.c
index 745380d4..507416e0 100644
--- a/examples/cwebp.c
+++ b/examples/cwebp.c
@@ -334,7 +334,7 @@ static int ReadPicture(const char* const filename, WebPPicture* const pic,
     } else if (format == JPEG_) {
       ok = ReadJPEG(in_file, pic);
     } else if (format == TIFF_) {
-      ok = ReadTIFF(filename, pic, keep_alpha);
+      ok = ReadTIFF(filename, pic, keep_alpha, metadata);
     }
   } else {
     // If image size is specified, infer it as YUV format.
diff --git a/examples/tiffdec.c b/examples/tiffdec.c
index c93be49a..6528a8ae 100644
--- a/examples/tiffdec.c
+++ b/examples/tiffdec.c
@@ -19,9 +19,51 @@
 #include <tiffio.h>
 
 #include "webp/encode.h"
+#include "./metadata.h"
+
+static const struct {
+  ttag_t tag;
+  size_t storage_offset;
+} kTIFFMetadataMap[] = {
+  { TIFFTAG_ICCPROFILE, METADATA_OFFSET(iccp) },
+  { TIFFTAG_XMLPACKET,  METADATA_OFFSET(xmp) },
+  { 0, 0 },
+};
+
+// Returns true on success. The caller must use MetadataFree() on 'metadata' in
+// all cases.
+static int ExtractMetadataFromTIFF(TIFF* const tif, Metadata* const metadata) {
+  int i;
+  uint32 exif_ifd_offset;
+
+  for (i = 0; kTIFFMetadataMap[i].tag != 0; ++i) {
+    MetadataPayload* const payload =
+        (MetadataPayload*)((uint8_t*)metadata +
+                           kTIFFMetadataMap[i].storage_offset);
+    void* tag_data;
+    uint32 tag_data_len;
+
+    if (TIFFGetField(tif, kTIFFMetadataMap[i].tag, &tag_data_len, &tag_data) &&
+        !MetadataCopy((const char*)tag_data, tag_data_len, payload)) {
+      return 0;
+    }
+  }
+
+  // TODO(jzern): To extract the raw EXIF directory some parsing of it would be
+  // necessary to determine the overall size. In addition, value offsets in
+  // individual directory entries may need to be updated as, depending on the
+  // type, they are file based.
+  // Exif 2.2 Section 4.6.2 Tag Structure
+  // TIFF Revision 6.0 Part 1 Section 2 TIFF Structure #Image File Directory
+  if (TIFFGetField(tif, TIFFTAG_EXIFIFD, &exif_ifd_offset)) {
+    fprintf(stderr, "Warning: EXIF extraction from TIFF is unsupported.\n");
+  }
+  return 1;
+}
 
 int ReadTIFF(const char* const filename,
-             WebPPicture* const pic, int keep_alpha) {
+             WebPPicture* const pic, int keep_alpha,
+             Metadata* const metadata) {
   TIFF* const tif = TIFFOpen(filename, "r");
   uint32 width, height;
   uint32* raster;
@@ -63,8 +105,18 @@ int ReadTIFF(const char* const filename,
     fprintf(stderr, "Error allocating TIFF RGBA memory!\n");
   }
 
-  if (ok && keep_alpha == 2) {
-    WebPCleanupTransparentArea(pic);
+  if (ok) {
+    if (keep_alpha == 2) {
+      WebPCleanupTransparentArea(pic);
+    }
+    if (metadata != NULL) {
+      ok = ExtractMetadataFromTIFF(tif, metadata);
+      if (!ok) {
+        fprintf(stderr, "Error extracting TIFF metadata!\n");
+        MetadataFree(metadata);
+        WebPPictureFree(pic);
+      }
+    }
   }
 
   TIFFClose(tif);
@@ -72,10 +124,12 @@ int ReadTIFF(const char* const filename,
 }
 #else  // !WEBP_HAVE_TIFF
 int ReadTIFF(const char* const filename,
-             struct WebPPicture* const pic, int keep_alpha) {
+             struct WebPPicture* const pic, int keep_alpha,
+             struct Metadata* const metadata) {
   (void)filename;
   (void)pic;
   (void)keep_alpha;
+  (void)metadata;
   fprintf(stderr, "TIFF support not compiled. Please install the libtiff "
           "development package before building.\n");
   return 0;
diff --git a/examples/tiffdec.h b/examples/tiffdec.h
index 1f0a7b2a..f441d5e0 100644
--- a/examples/tiffdec.h
+++ b/examples/tiffdec.h
@@ -14,6 +14,7 @@
 extern "C" {
 #endif
 
+struct Metadata;
 struct WebPPicture;
 
 // Reads a TIFF from 'filename', returning the decoded output in 'pic'.
@@ -21,7 +22,8 @@ struct WebPPicture;
 // otherwise it will be RGB.
 // Returns true on success.
 int ReadTIFF(const char* const filename,
-             struct WebPPicture* const pic, int keep_alpha);
+             struct WebPPicture* const pic, int keep_alpha,
+             struct Metadata* const metadata);
 
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"