55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
// Copyright (c) the JPEG XL Project Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "lib/extras/exif.h"
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#include "lib/jxl/base/byte_order.h"
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namespace jxl {
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constexpr uint16_t kExifOrientationTag = 274;
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void ResetExifOrientation(std::vector<uint8_t>& exif) {
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if (exif.size() < 12) return; // not enough bytes for a valid exif blob
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bool bigendian;
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uint8_t* t = exif.data();
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if (LoadLE32(t) == 0x2A004D4D) {
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bigendian = true;
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} else if (LoadLE32(t) == 0x002A4949) {
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bigendian = false;
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} else {
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return; // not a valid tiff header
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}
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t += 4;
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uint64_t offset = (bigendian ? LoadBE32(t) : LoadLE32(t));
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if (exif.size() < 12 + offset + 2 || offset < 8) return;
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t += offset - 4;
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uint16_t nb_tags = (bigendian ? LoadBE16(t) : LoadLE16(t));
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t += 2;
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while (nb_tags > 0) {
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if (t + 12 >= exif.data() + exif.size()) return;
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uint16_t tag = (bigendian ? LoadBE16(t) : LoadLE16(t));
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t += 2;
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if (tag == kExifOrientationTag) {
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uint16_t type = (bigendian ? LoadBE16(t) : LoadLE16(t));
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t += 2;
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uint32_t count = (bigendian ? LoadBE32(t) : LoadLE32(t));
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t += 4;
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if (type == 3 && count == 1) {
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if (bigendian) {
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StoreBE16(1, t);
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} else {
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StoreLE16(1, t);
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}
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}
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return;
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} else {
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t += 10;
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nb_tags--;
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}
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}
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}
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} // namespace jxl
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