xref: /aosp_15_r20/external/skia/src/codec/SkExif.cpp (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)
1*c8dee2aaSAndroid Build Coastguard Worker /*
2*c8dee2aaSAndroid Build Coastguard Worker  * Copyright 2023 Google Inc.
3*c8dee2aaSAndroid Build Coastguard Worker  *
4*c8dee2aaSAndroid Build Coastguard Worker  * Use of this source code is governed by a BSD-style license that can be
5*c8dee2aaSAndroid Build Coastguard Worker  * found in the LICENSE file.
6*c8dee2aaSAndroid Build Coastguard Worker  */
7*c8dee2aaSAndroid Build Coastguard Worker 
8*c8dee2aaSAndroid Build Coastguard Worker #include "include/private/SkExif.h"
9*c8dee2aaSAndroid Build Coastguard Worker 
10*c8dee2aaSAndroid Build Coastguard Worker #include "include/core/SkData.h"
11*c8dee2aaSAndroid Build Coastguard Worker #include "include/core/SkRefCnt.h"
12*c8dee2aaSAndroid Build Coastguard Worker #include "include/core/SkStream.h"
13*c8dee2aaSAndroid Build Coastguard Worker #include "src/codec/SkCodecPriv.h"
14*c8dee2aaSAndroid Build Coastguard Worker #include "src/codec/SkTiffUtility.h"
15*c8dee2aaSAndroid Build Coastguard Worker #include "src/core/SkStreamPriv.h"
16*c8dee2aaSAndroid Build Coastguard Worker 
17*c8dee2aaSAndroid Build Coastguard Worker #include <algorithm>
18*c8dee2aaSAndroid Build Coastguard Worker #include <cmath>
19*c8dee2aaSAndroid Build Coastguard Worker #include <cstring>
20*c8dee2aaSAndroid Build Coastguard Worker #include <memory>
21*c8dee2aaSAndroid Build Coastguard Worker #include <utility>
22*c8dee2aaSAndroid Build Coastguard Worker 
23*c8dee2aaSAndroid Build Coastguard Worker namespace SkExif {
24*c8dee2aaSAndroid Build Coastguard Worker 
25*c8dee2aaSAndroid Build Coastguard Worker constexpr uint16_t kSubIFDOffsetTag = 0x8769;
26*c8dee2aaSAndroid Build Coastguard Worker constexpr uint16_t kMarkerNoteTag = 0x927c;
27*c8dee2aaSAndroid Build Coastguard Worker 
get_maker_note_hdr_headroom(sk_sp<SkData> data)28*c8dee2aaSAndroid Build Coastguard Worker static std::optional<float> get_maker_note_hdr_headroom(sk_sp<SkData> data) {
29*c8dee2aaSAndroid Build Coastguard Worker     // No little endian images that specify this data have been observed. Do not add speculative
30*c8dee2aaSAndroid Build Coastguard Worker     // support.
31*c8dee2aaSAndroid Build Coastguard Worker     const bool kLittleEndian = false;
32*c8dee2aaSAndroid Build Coastguard Worker     const uint8_t kSig[] = {
33*c8dee2aaSAndroid Build Coastguard Worker             'A', 'p', 'p', 'l', 'e', ' ', 'i', 'O', 'S', 0, 0, 1, 'M', 'M',  //
34*c8dee2aaSAndroid Build Coastguard Worker     };
35*c8dee2aaSAndroid Build Coastguard Worker     if (!data || data->size() < sizeof(kSig)) {
36*c8dee2aaSAndroid Build Coastguard Worker         return std::nullopt;
37*c8dee2aaSAndroid Build Coastguard Worker     }
38*c8dee2aaSAndroid Build Coastguard Worker     if (memcmp(data->data(), kSig, sizeof(kSig)) != 0) {
39*c8dee2aaSAndroid Build Coastguard Worker         return std::nullopt;
40*c8dee2aaSAndroid Build Coastguard Worker     }
41*c8dee2aaSAndroid Build Coastguard Worker     auto ifd = SkTiff::ImageFileDirectory::MakeFromOffset(
42*c8dee2aaSAndroid Build Coastguard Worker             std::move(data), kLittleEndian, sizeof(kSig));
43*c8dee2aaSAndroid Build Coastguard Worker     if (!ifd) {
44*c8dee2aaSAndroid Build Coastguard Worker         return std::nullopt;
45*c8dee2aaSAndroid Build Coastguard Worker     }
46*c8dee2aaSAndroid Build Coastguard Worker 
47*c8dee2aaSAndroid Build Coastguard Worker     // See documentation at:
48*c8dee2aaSAndroid Build Coastguard Worker     // https://developer.apple.com/documentation/appkit/images_and_pdf/applying_apple_hdr_effect_to_your_photos
49*c8dee2aaSAndroid Build Coastguard Worker     bool hasMaker33 = false;
50*c8dee2aaSAndroid Build Coastguard Worker     bool hasMaker48 = false;
51*c8dee2aaSAndroid Build Coastguard Worker     float maker33 = 0.f;
52*c8dee2aaSAndroid Build Coastguard Worker     float maker48 = 0.f;
53*c8dee2aaSAndroid Build Coastguard Worker     for (uint32_t i = 0; i < ifd->getNumEntries(); ++i) {
54*c8dee2aaSAndroid Build Coastguard Worker         switch (ifd->getEntryTag(i)) {
55*c8dee2aaSAndroid Build Coastguard Worker             case 33:
56*c8dee2aaSAndroid Build Coastguard Worker                 if (!hasMaker33) {
57*c8dee2aaSAndroid Build Coastguard Worker                     hasMaker33 = ifd->getEntrySignedRational(i, 1, &maker33);
58*c8dee2aaSAndroid Build Coastguard Worker                 }
59*c8dee2aaSAndroid Build Coastguard Worker                 break;
60*c8dee2aaSAndroid Build Coastguard Worker             case 48:
61*c8dee2aaSAndroid Build Coastguard Worker                 if (!hasMaker48) {
62*c8dee2aaSAndroid Build Coastguard Worker                     hasMaker48 = ifd->getEntrySignedRational(i, 1, &maker48);
63*c8dee2aaSAndroid Build Coastguard Worker                 }
64*c8dee2aaSAndroid Build Coastguard Worker                 break;
65*c8dee2aaSAndroid Build Coastguard Worker             default:
66*c8dee2aaSAndroid Build Coastguard Worker                 break;
67*c8dee2aaSAndroid Build Coastguard Worker         }
68*c8dee2aaSAndroid Build Coastguard Worker     }
69*c8dee2aaSAndroid Build Coastguard Worker     // Many images have a maker33 but not a maker48. Treat them as having maker48 of 0.
70*c8dee2aaSAndroid Build Coastguard Worker     if (!hasMaker33) {
71*c8dee2aaSAndroid Build Coastguard Worker         return std::nullopt;
72*c8dee2aaSAndroid Build Coastguard Worker     }
73*c8dee2aaSAndroid Build Coastguard Worker     float stops = 0.f;
74*c8dee2aaSAndroid Build Coastguard Worker     if (maker33 < 1.0f) {
75*c8dee2aaSAndroid Build Coastguard Worker         if (maker48 <= 0.01f) {
76*c8dee2aaSAndroid Build Coastguard Worker             stops = -20.0f * maker48 + 1.8f;
77*c8dee2aaSAndroid Build Coastguard Worker         } else {
78*c8dee2aaSAndroid Build Coastguard Worker             stops = -0.101f * maker48 + 1.601f;
79*c8dee2aaSAndroid Build Coastguard Worker         }
80*c8dee2aaSAndroid Build Coastguard Worker     } else {
81*c8dee2aaSAndroid Build Coastguard Worker         if (maker48 <= 0.01f) {
82*c8dee2aaSAndroid Build Coastguard Worker             stops = -70.0f * maker48 + 3.0f;
83*c8dee2aaSAndroid Build Coastguard Worker         } else {
84*c8dee2aaSAndroid Build Coastguard Worker             stops = -0.303f * maker48 + 2.303f;
85*c8dee2aaSAndroid Build Coastguard Worker         }
86*c8dee2aaSAndroid Build Coastguard Worker     }
87*c8dee2aaSAndroid Build Coastguard Worker     return std::pow(2.f, std::max(stops, 0.f));
88*c8dee2aaSAndroid Build Coastguard Worker }
89*c8dee2aaSAndroid Build Coastguard Worker 
parse_ifd(Metadata & exif,sk_sp<SkData> data,std::unique_ptr<SkTiff::ImageFileDirectory> ifd,bool littleEndian,bool isRoot)90*c8dee2aaSAndroid Build Coastguard Worker static void parse_ifd(Metadata& exif,
91*c8dee2aaSAndroid Build Coastguard Worker                       sk_sp<SkData> data,
92*c8dee2aaSAndroid Build Coastguard Worker                       std::unique_ptr<SkTiff::ImageFileDirectory> ifd,
93*c8dee2aaSAndroid Build Coastguard Worker                       bool littleEndian,
94*c8dee2aaSAndroid Build Coastguard Worker                       bool isRoot) {
95*c8dee2aaSAndroid Build Coastguard Worker     if (!ifd) {
96*c8dee2aaSAndroid Build Coastguard Worker         return;
97*c8dee2aaSAndroid Build Coastguard Worker     }
98*c8dee2aaSAndroid Build Coastguard Worker     for (uint32_t i = 0; i < ifd->getNumEntries(); ++i) {
99*c8dee2aaSAndroid Build Coastguard Worker         switch (ifd->getEntryTag(i)) {
100*c8dee2aaSAndroid Build Coastguard Worker             case kOriginTag: {
101*c8dee2aaSAndroid Build Coastguard Worker                 uint16_t value = 0;
102*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fOrigin.has_value() && ifd->getEntryUnsignedShort(i, 1, &value)) {
103*c8dee2aaSAndroid Build Coastguard Worker                     if (0 < value && value <= kLast_SkEncodedOrigin) {
104*c8dee2aaSAndroid Build Coastguard Worker                         exif.fOrigin = static_cast<SkEncodedOrigin>(value);
105*c8dee2aaSAndroid Build Coastguard Worker                     }
106*c8dee2aaSAndroid Build Coastguard Worker                 }
107*c8dee2aaSAndroid Build Coastguard Worker                 break;
108*c8dee2aaSAndroid Build Coastguard Worker             }
109*c8dee2aaSAndroid Build Coastguard Worker             case kMarkerNoteTag:
110*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fHdrHeadroom.has_value()) {
111*c8dee2aaSAndroid Build Coastguard Worker                     if (auto makerNoteData = ifd->getEntryUndefinedData(i)) {
112*c8dee2aaSAndroid Build Coastguard Worker                         exif.fHdrHeadroom = get_maker_note_hdr_headroom(std::move(makerNoteData));
113*c8dee2aaSAndroid Build Coastguard Worker                     }
114*c8dee2aaSAndroid Build Coastguard Worker                 }
115*c8dee2aaSAndroid Build Coastguard Worker                 break;
116*c8dee2aaSAndroid Build Coastguard Worker             case kSubIFDOffsetTag: {
117*c8dee2aaSAndroid Build Coastguard Worker                 uint32_t subIfdOffset = 0;
118*c8dee2aaSAndroid Build Coastguard Worker                 if (isRoot && ifd->getEntryUnsignedLong(i, 1, &subIfdOffset)) {
119*c8dee2aaSAndroid Build Coastguard Worker                     auto subIfd = SkTiff::ImageFileDirectory::MakeFromOffset(
120*c8dee2aaSAndroid Build Coastguard Worker                             data, littleEndian, subIfdOffset, /*allowTruncated=*/true);
121*c8dee2aaSAndroid Build Coastguard Worker                     parse_ifd(exif,
122*c8dee2aaSAndroid Build Coastguard Worker                               data,
123*c8dee2aaSAndroid Build Coastguard Worker                               std::move(subIfd),
124*c8dee2aaSAndroid Build Coastguard Worker                               littleEndian,
125*c8dee2aaSAndroid Build Coastguard Worker                               /*isRoot=*/false);
126*c8dee2aaSAndroid Build Coastguard Worker                 }
127*c8dee2aaSAndroid Build Coastguard Worker                 break;
128*c8dee2aaSAndroid Build Coastguard Worker             }
129*c8dee2aaSAndroid Build Coastguard Worker             case kXResolutionTag: {
130*c8dee2aaSAndroid Build Coastguard Worker                 float value = 0.f;
131*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fXResolution.has_value() && ifd->getEntryUnsignedRational(i, 1, &value)) {
132*c8dee2aaSAndroid Build Coastguard Worker                     exif.fXResolution = value;
133*c8dee2aaSAndroid Build Coastguard Worker                 }
134*c8dee2aaSAndroid Build Coastguard Worker                 break;
135*c8dee2aaSAndroid Build Coastguard Worker             }
136*c8dee2aaSAndroid Build Coastguard Worker             case kYResolutionTag: {
137*c8dee2aaSAndroid Build Coastguard Worker                 float value = 0.f;
138*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fYResolution.has_value() && ifd->getEntryUnsignedRational(i, 1, &value)) {
139*c8dee2aaSAndroid Build Coastguard Worker                     exif.fYResolution = value;
140*c8dee2aaSAndroid Build Coastguard Worker                 }
141*c8dee2aaSAndroid Build Coastguard Worker                 break;
142*c8dee2aaSAndroid Build Coastguard Worker             }
143*c8dee2aaSAndroid Build Coastguard Worker             case kResolutionUnitTag: {
144*c8dee2aaSAndroid Build Coastguard Worker                 uint16_t value = 0;
145*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fResolutionUnit.has_value() && ifd->getEntryUnsignedShort(i, 1, &value)) {
146*c8dee2aaSAndroid Build Coastguard Worker                     exif.fResolutionUnit = value;
147*c8dee2aaSAndroid Build Coastguard Worker                 }
148*c8dee2aaSAndroid Build Coastguard Worker                 break;
149*c8dee2aaSAndroid Build Coastguard Worker             }
150*c8dee2aaSAndroid Build Coastguard Worker             case kPixelXDimensionTag: {
151*c8dee2aaSAndroid Build Coastguard Worker                 // The type for this tag can be unsigned short or unsigned long (as per the Exif 2.3
152*c8dee2aaSAndroid Build Coastguard Worker                 // spec, aka CIPA DC-008-2012). Support for unsigned long was added in
153*c8dee2aaSAndroid Build Coastguard Worker                 // https://crrev.com/817600.
154*c8dee2aaSAndroid Build Coastguard Worker                 uint16_t value16 = 0;
155*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fPixelXDimension.has_value() &&
156*c8dee2aaSAndroid Build Coastguard Worker                     ifd->getEntryUnsignedShort(i, 1, &value16)) {
157*c8dee2aaSAndroid Build Coastguard Worker                     exif.fPixelXDimension = value16;
158*c8dee2aaSAndroid Build Coastguard Worker                 }
159*c8dee2aaSAndroid Build Coastguard Worker                 uint32_t value32 = 0;
160*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fPixelXDimension.has_value() &&
161*c8dee2aaSAndroid Build Coastguard Worker                     ifd->getEntryUnsignedLong(i, 1, &value32)) {
162*c8dee2aaSAndroid Build Coastguard Worker                     exif.fPixelXDimension = value32;
163*c8dee2aaSAndroid Build Coastguard Worker                 }
164*c8dee2aaSAndroid Build Coastguard Worker                 break;
165*c8dee2aaSAndroid Build Coastguard Worker             }
166*c8dee2aaSAndroid Build Coastguard Worker             case kPixelYDimensionTag: {
167*c8dee2aaSAndroid Build Coastguard Worker                 uint16_t value16 = 0;
168*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fPixelYDimension.has_value() &&
169*c8dee2aaSAndroid Build Coastguard Worker                     ifd->getEntryUnsignedShort(i, 1, &value16)) {
170*c8dee2aaSAndroid Build Coastguard Worker                     exif.fPixelYDimension = value16;
171*c8dee2aaSAndroid Build Coastguard Worker                 }
172*c8dee2aaSAndroid Build Coastguard Worker                 uint32_t value32 = 0;
173*c8dee2aaSAndroid Build Coastguard Worker                 if (!exif.fPixelYDimension.has_value() &&
174*c8dee2aaSAndroid Build Coastguard Worker                     ifd->getEntryUnsignedLong(i, 1, &value32)) {
175*c8dee2aaSAndroid Build Coastguard Worker                     exif.fPixelYDimension = value32;
176*c8dee2aaSAndroid Build Coastguard Worker                 }
177*c8dee2aaSAndroid Build Coastguard Worker                 break;
178*c8dee2aaSAndroid Build Coastguard Worker             }
179*c8dee2aaSAndroid Build Coastguard Worker             default:
180*c8dee2aaSAndroid Build Coastguard Worker                 break;
181*c8dee2aaSAndroid Build Coastguard Worker         }
182*c8dee2aaSAndroid Build Coastguard Worker     }
183*c8dee2aaSAndroid Build Coastguard Worker }
184*c8dee2aaSAndroid Build Coastguard Worker 
Parse(Metadata & metadata,const SkData * data)185*c8dee2aaSAndroid Build Coastguard Worker void Parse(Metadata& metadata, const SkData* data) {
186*c8dee2aaSAndroid Build Coastguard Worker     bool littleEndian = false;
187*c8dee2aaSAndroid Build Coastguard Worker     uint32_t ifdOffset = 0;
188*c8dee2aaSAndroid Build Coastguard Worker     if (data && SkTiff::ImageFileDirectory::ParseHeader(data, &littleEndian, &ifdOffset)) {
189*c8dee2aaSAndroid Build Coastguard Worker         auto dataRef = SkData::MakeWithoutCopy(data->data(), data->size());
190*c8dee2aaSAndroid Build Coastguard Worker         auto ifd = SkTiff::ImageFileDirectory::MakeFromOffset(
191*c8dee2aaSAndroid Build Coastguard Worker                 dataRef, littleEndian, ifdOffset, /*allowTruncated=*/true);
192*c8dee2aaSAndroid Build Coastguard Worker         parse_ifd(metadata, std::move(dataRef), std::move(ifd), littleEndian, /*isRoot=*/true);
193*c8dee2aaSAndroid Build Coastguard Worker     }
194*c8dee2aaSAndroid Build Coastguard Worker }
195*c8dee2aaSAndroid Build Coastguard Worker 
196*c8dee2aaSAndroid Build Coastguard Worker // Helper function to write a single IFD entry.
write_entry(uint16_t tag,uint16_t type,uint32_t count,uint32_t value,uint32_t * endOfData,SkWStream * stream,SkWStream * buffer)197*c8dee2aaSAndroid Build Coastguard Worker bool write_entry(uint16_t tag, uint16_t type, uint32_t count, uint32_t value,
198*c8dee2aaSAndroid Build Coastguard Worker                 uint32_t* endOfData, SkWStream* stream, SkWStream* buffer) {
199*c8dee2aaSAndroid Build Coastguard Worker     bool success = true;
200*c8dee2aaSAndroid Build Coastguard Worker     success &= SkWStreamWriteU16BE(stream, tag);
201*c8dee2aaSAndroid Build Coastguard Worker     success &= SkWStreamWriteU16BE(stream, type);
202*c8dee2aaSAndroid Build Coastguard Worker     success &= SkWStreamWriteU32BE(stream, count);
203*c8dee2aaSAndroid Build Coastguard Worker     switch (tag) {
204*c8dee2aaSAndroid Build Coastguard Worker       case kOriginTag:
205*c8dee2aaSAndroid Build Coastguard Worker       case kResolutionUnitTag:
206*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU16BE(stream, value);
207*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU16BE(stream, 0); // Complete the IFD entry.
208*c8dee2aaSAndroid Build Coastguard Worker         return success;
209*c8dee2aaSAndroid Build Coastguard Worker       case kPixelXDimensionTag:
210*c8dee2aaSAndroid Build Coastguard Worker       case kPixelYDimensionTag:
211*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU32BE(stream, value);
212*c8dee2aaSAndroid Build Coastguard Worker         return success;
213*c8dee2aaSAndroid Build Coastguard Worker       case kXResolutionTag:
214*c8dee2aaSAndroid Build Coastguard Worker       case kYResolutionTag:
215*c8dee2aaSAndroid Build Coastguard Worker         // If the number of bytes for the type of the entry is greater than 4, we have
216*c8dee2aaSAndroid Build Coastguard Worker         // to append the value to the end and replace the value section with an offset
217*c8dee2aaSAndroid Build Coastguard Worker         // to where the data can be found.
218*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU32BE(stream, *endOfData);
219*c8dee2aaSAndroid Build Coastguard Worker         *endOfData += 8;
220*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU32BE(buffer, value); // Numerator
221*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU32BE(buffer, 1); // Denominator
222*c8dee2aaSAndroid Build Coastguard Worker         return success;
223*c8dee2aaSAndroid Build Coastguard Worker       case kSubIFDOffsetTag:
224*c8dee2aaSAndroid Build Coastguard Worker         // This does not write the subIFD itself, just the IFD0 entry that points
225*c8dee2aaSAndroid Build Coastguard Worker         // to where it is located.
226*c8dee2aaSAndroid Build Coastguard Worker         success &= SkWStreamWriteU32BE(stream, value);
227*c8dee2aaSAndroid Build Coastguard Worker         return success;
228*c8dee2aaSAndroid Build Coastguard Worker       default:
229*c8dee2aaSAndroid Build Coastguard Worker         return false;
230*c8dee2aaSAndroid Build Coastguard Worker     }
231*c8dee2aaSAndroid Build Coastguard Worker }
232*c8dee2aaSAndroid Build Coastguard Worker 
WriteExif(Metadata & metadata)233*c8dee2aaSAndroid Build Coastguard Worker sk_sp<SkData> WriteExif(Metadata& metadata) {
234*c8dee2aaSAndroid Build Coastguard Worker     // Cannot write an IFD entry for MakerNote from the HDR Headroom. Information
235*c8dee2aaSAndroid Build Coastguard Worker     // about maker48 and maker33 is lost in encode.
236*c8dee2aaSAndroid Build Coastguard Worker     // See documentation at:
237*c8dee2aaSAndroid Build Coastguard Worker     // https://developer.apple.com/documentation/appkit/images_and_pdf/applying_apple_hdr_effect_to_your_photos
238*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fHdrHeadroom.has_value()) {
239*c8dee2aaSAndroid Build Coastguard Worker         SkCodecPrintf("Cannot encode maker noter from the headroom value.\n");
240*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
241*c8dee2aaSAndroid Build Coastguard Worker     }
242*c8dee2aaSAndroid Build Coastguard Worker 
243*c8dee2aaSAndroid Build Coastguard Worker     SkDynamicMemoryWStream stream;
244*c8dee2aaSAndroid Build Coastguard Worker     // If there exists metadata that belongs in a subIFD, we will write that to a
245*c8dee2aaSAndroid Build Coastguard Worker     // separate stream and append it to the end of the data, before |bufferForLargerValues|.
246*c8dee2aaSAndroid Build Coastguard Worker     bool subIFDExists = false;
247*c8dee2aaSAndroid Build Coastguard Worker     // This buffer will hold the values that are more than 4 bytes and will be
248*c8dee2aaSAndroid Build Coastguard Worker     // appended to the end of the data after going through all available fields.
249*c8dee2aaSAndroid Build Coastguard Worker     SkDynamicMemoryWStream bufferForLargerValues;
250*c8dee2aaSAndroid Build Coastguard Worker     constexpr uint32_t kOffset = 8;
251*c8dee2aaSAndroid Build Coastguard Worker 
252*c8dee2aaSAndroid Build Coastguard Worker     // Write the IFD header.
253*c8dee2aaSAndroid Build Coastguard Worker     if (!stream.write(SkTiff::kEndianBig, sizeof(SkTiff::kEndianBig))) {
254*c8dee2aaSAndroid Build Coastguard Worker       return nullptr;
255*c8dee2aaSAndroid Build Coastguard Worker     }
256*c8dee2aaSAndroid Build Coastguard Worker     // Offset of index IFD.
257*c8dee2aaSAndroid Build Coastguard Worker     if (!SkWStreamWriteU32BE(&stream, kOffset)) {
258*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
259*c8dee2aaSAndroid Build Coastguard Worker     }
260*c8dee2aaSAndroid Build Coastguard Worker     // Count the number of valid metadata entries.
261*c8dee2aaSAndroid Build Coastguard Worker     uint16_t numTags = 0;
262*c8dee2aaSAndroid Build Coastguard Worker     uint16_t numSubIFDTags = 0;
263*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fOrigin.has_value()) numTags++;
264*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fResolutionUnit.has_value()) numTags++;
265*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fXResolution.has_value()) numTags++;
266*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fYResolution.has_value()) numTags++;
267*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fPixelXDimension.has_value()) numSubIFDTags++;
268*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fPixelYDimension.has_value()) numSubIFDTags++;
269*c8dee2aaSAndroid Build Coastguard Worker     if (numSubIFDTags > 0) {
270*c8dee2aaSAndroid Build Coastguard Worker       subIFDExists = true;
271*c8dee2aaSAndroid Build Coastguard Worker       numTags++;
272*c8dee2aaSAndroid Build Coastguard Worker     }
273*c8dee2aaSAndroid Build Coastguard Worker 
274*c8dee2aaSAndroid Build Coastguard Worker     // Offset that represents where data will be appended.
275*c8dee2aaSAndroid Build Coastguard Worker     uint32_t endOfData = kOffset
276*c8dee2aaSAndroid Build Coastguard Worker                         + SkTiff::kSizeShort  // Number of tags
277*c8dee2aaSAndroid Build Coastguard Worker                         + (SkTiff::kSizeEntry * numTags) // Entries
278*c8dee2aaSAndroid Build Coastguard Worker                         + SkTiff::kSizeLong; // Next IFD offset
279*c8dee2aaSAndroid Build Coastguard Worker     // Offset that represents where the subIFD will start if it exists.
280*c8dee2aaSAndroid Build Coastguard Worker     const uint32_t kSubIfdOffset = endOfData;
281*c8dee2aaSAndroid Build Coastguard Worker     if (subIFDExists) {
282*c8dee2aaSAndroid Build Coastguard Worker       endOfData += SkTiff::kSizeShort  // Number of subIFD tags
283*c8dee2aaSAndroid Build Coastguard Worker                   + (SkTiff::kSizeEntry * numSubIFDTags) // SubIFD entries
284*c8dee2aaSAndroid Build Coastguard Worker                   + SkTiff::kSizeLong; // SubIFD next offset;
285*c8dee2aaSAndroid Build Coastguard Worker     }
286*c8dee2aaSAndroid Build Coastguard Worker 
287*c8dee2aaSAndroid Build Coastguard Worker     // Write the number of tags in the IFD.
288*c8dee2aaSAndroid Build Coastguard Worker     SkWStreamWriteU16BE(&stream, numTags);
289*c8dee2aaSAndroid Build Coastguard Worker 
290*c8dee2aaSAndroid Build Coastguard Worker     // Write the IFD entries.
291*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fOrigin.has_value()
292*c8dee2aaSAndroid Build Coastguard Worker         && !write_entry(kOriginTag, SkTiff::kTypeUnsignedShort, 1,
293*c8dee2aaSAndroid Build Coastguard Worker                         metadata.fOrigin.value(), &endOfData, &stream,
294*c8dee2aaSAndroid Build Coastguard Worker                         &bufferForLargerValues)) {
295*c8dee2aaSAndroid Build Coastguard Worker           return nullptr;
296*c8dee2aaSAndroid Build Coastguard Worker         }
297*c8dee2aaSAndroid Build Coastguard Worker 
298*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fResolutionUnit.has_value()
299*c8dee2aaSAndroid Build Coastguard Worker         && !write_entry(kResolutionUnitTag, SkTiff::kTypeUnsignedShort, 1,
300*c8dee2aaSAndroid Build Coastguard Worker                         metadata.fResolutionUnit.value(), &endOfData, &stream,
301*c8dee2aaSAndroid Build Coastguard Worker                         &bufferForLargerValues)) {
302*c8dee2aaSAndroid Build Coastguard Worker           return nullptr;
303*c8dee2aaSAndroid Build Coastguard Worker         }
304*c8dee2aaSAndroid Build Coastguard Worker 
305*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fXResolution.has_value()
306*c8dee2aaSAndroid Build Coastguard Worker         && !write_entry(kXResolutionTag, SkTiff::kTypeUnsignedRational, 1,
307*c8dee2aaSAndroid Build Coastguard Worker                         metadata.fXResolution.value(), &endOfData, &stream,
308*c8dee2aaSAndroid Build Coastguard Worker                         &bufferForLargerValues)) {
309*c8dee2aaSAndroid Build Coastguard Worker           return nullptr;
310*c8dee2aaSAndroid Build Coastguard Worker         }
311*c8dee2aaSAndroid Build Coastguard Worker 
312*c8dee2aaSAndroid Build Coastguard Worker     if (metadata.fYResolution.has_value()
313*c8dee2aaSAndroid Build Coastguard Worker         && !write_entry(kYResolutionTag, SkTiff::kTypeUnsignedRational, 1,
314*c8dee2aaSAndroid Build Coastguard Worker                         metadata.fYResolution.value(), &endOfData, &stream,
315*c8dee2aaSAndroid Build Coastguard Worker                         &bufferForLargerValues)) {
316*c8dee2aaSAndroid Build Coastguard Worker           return nullptr;
317*c8dee2aaSAndroid Build Coastguard Worker         }
318*c8dee2aaSAndroid Build Coastguard Worker 
319*c8dee2aaSAndroid Build Coastguard Worker     if (subIFDExists && !write_entry(kSubIFDOffsetTag, SkTiff::kTypeUnsignedLong, 1,
320*c8dee2aaSAndroid Build Coastguard Worker                       kSubIfdOffset, &endOfData, &stream, &bufferForLargerValues)) {
321*c8dee2aaSAndroid Build Coastguard Worker           return nullptr;
322*c8dee2aaSAndroid Build Coastguard Worker         }
323*c8dee2aaSAndroid Build Coastguard Worker 
324*c8dee2aaSAndroid Build Coastguard Worker     // Next IFD offset (0 for no next IFD).
325*c8dee2aaSAndroid Build Coastguard Worker     if (!SkWStreamWriteU32BE(&stream, 0)) {
326*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
327*c8dee2aaSAndroid Build Coastguard Worker     }
328*c8dee2aaSAndroid Build Coastguard Worker 
329*c8dee2aaSAndroid Build Coastguard Worker     // After all IFD0 data has been written, then write the SubIFD (ExifIFD).
330*c8dee2aaSAndroid Build Coastguard Worker     if (subIFDExists) {
331*c8dee2aaSAndroid Build Coastguard Worker       // Write the number of tags in the subIFD.
332*c8dee2aaSAndroid Build Coastguard Worker       if (!SkWStreamWriteU16BE(&stream, numSubIFDTags)) {
333*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
334*c8dee2aaSAndroid Build Coastguard Worker       }
335*c8dee2aaSAndroid Build Coastguard Worker 
336*c8dee2aaSAndroid Build Coastguard Worker       if (metadata.fPixelXDimension.has_value()
337*c8dee2aaSAndroid Build Coastguard Worker           && !write_entry(kPixelXDimensionTag, SkTiff::kTypeUnsignedLong, 1,
338*c8dee2aaSAndroid Build Coastguard Worker                           metadata.fPixelXDimension.value(), &endOfData, &stream,
339*c8dee2aaSAndroid Build Coastguard Worker                           &bufferForLargerValues)) {
340*c8dee2aaSAndroid Build Coastguard Worker             return nullptr;
341*c8dee2aaSAndroid Build Coastguard Worker           }
342*c8dee2aaSAndroid Build Coastguard Worker 
343*c8dee2aaSAndroid Build Coastguard Worker       if (metadata.fPixelYDimension.has_value()
344*c8dee2aaSAndroid Build Coastguard Worker           && !write_entry(kPixelYDimensionTag, SkTiff::kTypeUnsignedLong, 1,
345*c8dee2aaSAndroid Build Coastguard Worker                           metadata.fPixelYDimension.value(), &endOfData, &stream,
346*c8dee2aaSAndroid Build Coastguard Worker                           &bufferForLargerValues)) {
347*c8dee2aaSAndroid Build Coastguard Worker             return nullptr;
348*c8dee2aaSAndroid Build Coastguard Worker           }
349*c8dee2aaSAndroid Build Coastguard Worker 
350*c8dee2aaSAndroid Build Coastguard Worker       // Write the SubIFD next offset (0).
351*c8dee2aaSAndroid Build Coastguard Worker       if (!SkWStreamWriteU32BE(&stream, 0)) {
352*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
353*c8dee2aaSAndroid Build Coastguard Worker       }
354*c8dee2aaSAndroid Build Coastguard Worker     }
355*c8dee2aaSAndroid Build Coastguard Worker 
356*c8dee2aaSAndroid Build Coastguard Worker     // Append the data buffer to the end of the stream.
357*c8dee2aaSAndroid Build Coastguard Worker     if (!bufferForLargerValues.writeToStream(&stream)) {
358*c8dee2aaSAndroid Build Coastguard Worker         return nullptr;
359*c8dee2aaSAndroid Build Coastguard Worker     }
360*c8dee2aaSAndroid Build Coastguard Worker 
361*c8dee2aaSAndroid Build Coastguard Worker     return stream.detachAsData();
362*c8dee2aaSAndroid Build Coastguard Worker }
363*c8dee2aaSAndroid Build Coastguard Worker 
364*c8dee2aaSAndroid Build Coastguard Worker }  // namespace SkExif
365