From 1e816ebefee0ef479fa76bd2a1fb9ec5d5e807df Mon Sep 17 00:00:00 2001
From: Leo Izen <leo.izen@gmail.com>
Date: Wed, 9 Apr 2025 13:07:49 -0400
Subject: [PATCH] avcodec/tiff: decode TIFF non-image-data tags into EXIF
 metadata struct

This commit will cause TIFF files to store their tags in the EXIF
struct so tags such as orientation can be transfered to other formats
(such as PNG) in a way that doesn't corrupt the IFD.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
---
 libavcodec/tiff.c              | 14 ++++++++++++++
 tests/ref/fate/exif-image-tiff | 24 +++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index b468598fbb..d15bc497ec 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -47,6 +47,7 @@
 #include "bytestream.h"
 #include "codec_internal.h"
 #include "decode.h"
+#include "exif_internal.h"
 #include "faxcompr.h"
 #include "lzw.h"
 #include "tiff.h"
@@ -124,6 +125,8 @@ typedef struct TiffContext {
 
     int geotag_count;
     TiffGeoTag *geotags;
+
+    AVExifMetadata exif_meta;
 } TiffContext;
 
 static const float d65_white[3] = { 0.950456f, 1.f, 1.088754f };
@@ -1937,6 +1940,12 @@ static int decode_frame(AVCodecContext *avctx, AVFrame *p,
     int is_dng;
     int has_tile_bits, has_strip_bits;
 
+    av_exif_free(&s->exif_meta);
+    /* this will not parse the image data */
+    ret = av_exif_parse_buffer(avctx, avpkt->data, avpkt->size, &s->exif_meta, AV_EXIF_TIFF_HEADER);
+    if (ret < 0)
+        av_log(avctx, AV_LOG_ERROR, "could not parse EXIF data: %s\n", av_err2str(ret));
+
     bytestream2_init(&s->gb, avpkt->data, avpkt->size);
 
     // parse image header
@@ -2402,6 +2411,10 @@ again:
         }
     }
 
+    ret = ff_exif_attach_ifd(avctx, p, &s->exif_meta);
+    if (ret < 0)
+        av_log(avctx, AV_LOG_ERROR, "error attaching EXIF ifd: %s\n", av_err2str(ret));
+
     *got_frame = 1;
 
     return avpkt->size;
@@ -2450,6 +2463,7 @@ static av_cold int tiff_end(AVCodecContext *avctx)
     TiffContext *const s = avctx->priv_data;
 
     free_geotags(s);
+    av_exif_free(&s->exif_meta);
 
     ff_lzw_decode_close(&s->lzw);
     av_freep(&s->deinvert_buf);
diff --git a/tests/ref/fate/exif-image-tiff b/tests/ref/fate/exif-image-tiff
index 0e604d4271..81737cb983 100644
--- a/tests/ref/fate/exif-image-tiff
+++ b/tests/ref/fate/exif-image-tiff
@@ -32,5 +32,27 @@ color_transfer=unknown
 chroma_location=unspecified
 TAG:document_name=image_small.tiff
 TAG:page_number=    0 /     1
-TAG:software=ImageMagick 6.5.8-0 2010-02-09 Q16 http://www.imagemagick.org
+TAG:0x0129=      0,       1
+TAG:ImageWidth=    200
+TAG:ImageLength=    112
+TAG:BitsPerSample=      8,       8,       8
+TAG:Compression=      1
+TAG:PhotometricInterpretation=      2
+TAG:0x010A=      1
+TAG:0x010D=image_small.tiff
+TAG:StripOffsets=      8,    7808,   15608,   23408,   31208,   39008,   46808,   54608
+  62408
+TAG:Orientation=      1
+TAG:SamplesPerPixel=      3
+TAG:RowsPerStrip=     13
+TAG:StripByteCounts=   7800,    7800,    7800,    7800,    7800,    7800,    7800,    7800
+   4800
+TAG:XResolution=1188833536:16777216
+TAG:YResolution=1188833536:16777216
+TAG:PlanarConfiguration=      1
+TAG:ResolutionUnit=      3
+TAG:Software=ImageMagick 6.5.8-0 2010-02-09 Q16 http://www.imagemagick.org
+[SIDE_DATA]
+side_data_type=EXIF metadata
+[/SIDE_DATA]
 [/FRAME]