/src/libjxl/lib/extras/exif.cc
Line | Count | Source |
1 | | // Copyright (c) the JPEG XL Project Authors. All rights reserved. |
2 | | // |
3 | | // Use of this source code is governed by a BSD-style |
4 | | // license that can be found in the LICENSE file. |
5 | | |
6 | | #include "lib/extras/exif.h" |
7 | | |
8 | | #include <cstdint> |
9 | | #include <vector> |
10 | | |
11 | | #include "lib/jxl/base/byte_order.h" |
12 | | |
13 | | namespace jxl { |
14 | | |
15 | | constexpr uint16_t kExifOrientationTag = 274; |
16 | | |
17 | 38 | void ResetExifOrientation(std::vector<uint8_t>& exif) { |
18 | 38 | if (exif.size() < 12) return; // not enough bytes for a valid exif blob |
19 | 38 | bool bigendian; |
20 | 38 | uint8_t* t = exif.data(); |
21 | 38 | if (LoadLE32(t) == 0x2A004D4D) { |
22 | 18 | bigendian = true; |
23 | 20 | } else if (LoadLE32(t) == 0x002A4949) { |
24 | 20 | bigendian = false; |
25 | 20 | } else { |
26 | 0 | return; // not a valid tiff header |
27 | 0 | } |
28 | 38 | t += 4; |
29 | 38 | uint64_t offset = (bigendian ? LoadBE32(t) : LoadLE32(t)); |
30 | 38 | if (exif.size() < 12 + offset + 2 || offset < 8) return; |
31 | 35 | t += offset - 4; |
32 | 35 | uint16_t nb_tags = (bigendian ? LoadBE16(t) : LoadLE16(t)); |
33 | 35 | t += 2; |
34 | 799 | while (nb_tags > 0) { |
35 | 795 | if (t + 12 >= exif.data() + exif.size()) return; |
36 | 775 | uint16_t tag = (bigendian ? LoadBE16(t) : LoadLE16(t)); |
37 | 775 | t += 2; |
38 | 775 | if (tag == kExifOrientationTag) { |
39 | 11 | uint16_t type = (bigendian ? LoadBE16(t) : LoadLE16(t)); |
40 | 11 | t += 2; |
41 | 11 | uint32_t count = (bigendian ? LoadBE32(t) : LoadLE32(t)); |
42 | 11 | t += 4; |
43 | 11 | if (type == 3 && count == 1) { |
44 | 5 | if (bigendian) { |
45 | 1 | StoreBE16(1, t); |
46 | 4 | } else { |
47 | 4 | StoreLE16(1, t); |
48 | 4 | } |
49 | 5 | } |
50 | 11 | return; |
51 | 764 | } else { |
52 | 764 | t += 10; |
53 | 764 | nb_tags--; |
54 | 764 | } |
55 | 775 | } |
56 | 35 | } |
57 | | |
58 | | } // namespace jxl |