blob: cd5178e17d2f881eaf0f1b6fafff1541da8cfc57 [file] [log] [blame]
* Copyright 2023 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkTiffUtility_codec_DEFINED
#define SkTiffUtility_codec_DEFINED
#include "include/core/SkData.h"
#include "include/core/SkRefCnt.h"
#include <cstddef>
#include <cstdint>
#include <memory>
* Helper function for parsing a Tiff Image File Directory (IFD) structure. This structure is used
* by EXIF tags, multi-picture, and maker note metadata.
class SkTiffImageFileDirectory {
* Parse |data| to read the endian-ness into |outLittleEndian| and the IFD offset into
* |outIfdOffset|. Return true if the endian-ness was successfully parsed and there was
* the IFD offset was read.
static bool ParseHeader(const SkData* data, bool* outLittleEndian, uint32_t* outIfdOffset);
* Create an object for parsing an IFD at offset |ifdOffset| inside |data| which has endianness
* indicated by |littleEndian|.
static std::unique_ptr<SkTiffImageFileDirectory> MakeFromOffset(sk_sp<SkData> data,
bool littleEndian,
uint32_t ifdOffset);
* Return the number of entries.
uint16_t getNumEntries() const { return fNumEntries; }
* Return the offset (within the specified SkData) of the next IFD in the list of IFDs.
uint32_t nextIfdOffset() const { return fNextIfdOffset; }
* Return the tag, of a specific entry.
uint16_t getEntryTag(uint16_t entryIndex) const;
* If |entryIndex| has type unsigned short (3), unsigned long (4), or signed rational (10), and
* count |count|, then populate |values| with the data for the tag and return true. Otherwise
* return false.
bool getEntryUnsignedShort(uint16_t entryIndex, uint32_t count, uint16_t* values) const {
return getEntryValuesGeneric(entryIndex, kTypeUnsignedShort, count, values);
bool getEntryUnsignedLong(uint16_t entryIndex, uint32_t count, uint32_t* values) const {
return getEntryValuesGeneric(entryIndex, kTypeUnsignedLong, count, values);
bool getEntrySignedRational(uint16_t entryIndex, uint32_t count, float* values) const {
return getEntryValuesGeneric(entryIndex, kTypeSignedRational, count, values);
bool getEntryUnsignedRational(uint16_t entryIndex, uint32_t count, float* values) const {
return getEntryValuesGeneric(entryIndex, kTypeUnsignedRational, count, values);
* If |entryIndex| has type undefined (7), then return the bytes specified by the count field
* and the offset (read from the value field as an unsigned long).
sk_sp<SkData> getEntryUndefinedData(uint16_t entryIndex) const;
static constexpr uint16_t kTypeUnsignedByte = 1;
static constexpr uint16_t kTypeAsciiString = 2;
static constexpr uint16_t kTypeUnsignedShort = 3;
static constexpr uint16_t kTypeUnsignedLong = 4;
static constexpr uint16_t kTypeUnsignedRational = 5;
static constexpr uint16_t kTypeSignedByte = 6;
static constexpr uint16_t kTypeUndefined = 7;
static constexpr uint16_t kTypeSignedShort = 8;
static constexpr uint16_t kTypeSignedLong = 9;
static constexpr uint16_t kTypeSignedRational = 10;
static constexpr uint16_t kTypeSingleFloat = 11;
static constexpr uint16_t kTypeDoubleFloat = 12;
static bool IsValidType(uint16_t type);
static size_t BytesForType(uint16_t type);
SkTiffImageFileDirectory(sk_sp<SkData> data,
bool littleEndian,
uint32_t offset,
uint16_t ifdNumEntries,
uint32_t ifdNextOffset);
* Return the tag, type, count, and data for the specified entry. Return false if the type
* is invalid, or if the data in the IFD is out of bounds.
bool getEntryRawData(uint16_t entryIndex,
uint16_t* outTag,
uint16_t* outType,
uint32_t* outCount,
const uint8_t** outData,
size_t* outDataSize) const;
* Helper function for assorted getTag functions.
bool getEntryValuesGeneric(uint16_t entryIndex,
uint16_t type,
uint32_t count,
void* values) const;
// The data that the IFD indexes into.
const sk_sp<SkData> fData;
// True if the data is little endian.
const bool fLittleEndian;
// The offset where the IFD starts.
const uint32_t fOffset;
// The number of entries of the IFD (read from the first 2 bytes at the IFD offset).
const uint16_t fNumEntries;
// The offset of the next IFD (read from the next 4 bytes after the IFD entries).
const uint32_t fNextIfdOffset;