avcodec: Add EXIF metadata parser to libavcodec.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 130 insertions, 0 deletions

diff --git a/libavcodec/exif.c b/libavcodec/exif.c
new file mode 100644
index 0000000000..90a058621b
--- /dev/null
+++ b/libavcodec/exif.c
@@ -0,0 +1,130 @@
+/*
+ * EXIF metadata parser
+ * Copyright (c) 2013 Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * EXIF metadata parser
+ * @author Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
+ */
+
+#include "exif.h"
+
+
+static const char *exif_get_tag_name(uint16_t id)
+{
+    int i;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(tag_list); i++) {
+        if (tag_list[i].id == id)
+            return tag_list[i].name;
+    }
+
+    return NULL;
+}
+
+
+static int exif_add_metadata(AVCodecContext *avctx, int count, int type,
+                             const char *name, const char *sep,
+                             GetByteContext *gb, int le,
+                             AVDictionary **metadata)
+{
+    switch(type) {
+    case TIFF_DOUBLE   : return ff_tadd_doubles_metadata(count, name, sep, gb, le, metadata);
+    case TIFF_SHORT    : return ff_tadd_shorts_metadata(count, name, sep, gb, le, metadata);
+    case TIFF_BYTE     :
+    case TIFF_UNDEFINED:
+    case TIFF_STRING   : return ff_tadd_string_metadata(count, name, gb, le, metadata);
+    case TIFF_SRATIONAL:
+    case TIFF_RATIONAL : return ff_tadd_rational_metadata(count, name, sep, gb, le, metadata);
+    case TIFF_SLONG    :
+    case TIFF_LONG     : return ff_tadd_long_metadata(count, name, sep, gb, le, metadata);
+    default:
+        avpriv_request_sample(avctx, "TIFF tag type (%u)", type);
+        return 0;
+    };
+}
+
+
+static int exif_decode_tag(AVCodecContext *avctx, GetByteContext *gbytes, int le,
+                           int depth, AVDictionary **metadata)
+{
+    int ret, cur_pos;
+    unsigned id, count;
+    enum TiffTypes type;
+
+    if (depth > 2) {
+        return 0;
+    }
+
+    ff_tread_tag(gbytes, le, &id, &type, &count, &cur_pos);
+
+    // read count values and add it metadata
+    // store metadata or proceed with next IFD
+    ret = ff_tis_ifd(id);
+    if (ret) {
+        ret = ff_exif_decode_ifd(avctx, gbytes, le, depth + 1, metadata);
+    } else {
+        const char *name = exif_get_tag_name(id);
+        char *use_name   = (char*) name;
+
+        if (!use_name) {
+            use_name = av_malloc(7);
+            if (!use_name) {
+                return AVERROR(ENOMEM);
+            }
+            snprintf(use_name, 7, "0x%04X", id);
+        }
+
+        ret = exif_add_metadata(avctx, count, type, use_name, NULL,
+                                gbytes, le, metadata);
+
+        if (!name) {
+            av_freep(&use_name);
+        }
+    }
+
+    bytestream2_seek(gbytes, cur_pos, SEEK_SET);
+
+    return ret;
+}
+
+
+int ff_exif_decode_ifd(AVCodecContext *avctx, GetByteContext *gbytes, int le,
+                       int depth, AVDictionary **metadata)
+{
+    int i, ret;
+    int entries;
+
+    entries = ff_tget_short(gbytes, le);
+
+    if (bytestream2_get_bytes_left(gbytes) < entries * 12) {
+        return AVERROR_INVALIDDATA;
+    }
+
+    for (i = 0; i < entries; i++) {
+        if ((ret = exif_decode_tag(avctx, gbytes, le, depth, metadata)) < 0) {
+            return ret;
+        }
+    }
+
+    // return next IDF offset or 0x000000000 or a value < 0 for failure
+    return ff_tget_long(gbytes, le);
+}