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* 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 SkJpegMultiPicture_codec_DEFINED
#define SkJpegMultiPicture_codec_DEFINED
#include "include/core/SkRefCnt.h"
#include <cstdint>
#include <memory>
#include <vector>
class SkData;
* Parsed Jpeg Multi-Picture Format structure as specified in CIPA DC-x007-2009. An introduction to
* the format can be found in Figure 1 (Basic MP File format data structure) and Figure 6 (Internal
* Structure of the MP Index IFD) in that document. This parsing will extract only the size and
* offset parameters from the images in the Index Image File Directory.
struct SkJpegMultiPictureParameters {
explicit SkJpegMultiPictureParameters(size_t numberOfImages) : images(numberOfImages) {}
// An individual image.
struct Image {
// The size of the image in bytes.
uint32_t size = 0;
// The offset of the image in bytes. This offset is specified relative to the address of
// the MP Endian field in the MP Header, unless the image is a First Individual Image, in
// which case the value of the offest [sic] shall be NULL (from section
uint32_t dataOffset = 0;
// The images listed in the Index Image File Directory.
std::vector<Image> images;
* Parse Jpeg Multi-Picture Format parameters. The specified data should be APP2 segment
* parameters, which, if they are MPF parameter, should start with the {'M', 'P', 'F', 0}
* signature. Returns nullptr the parameters do not start with the MPF signature, or if there
* is an error in parsing the parameters.
static std::unique_ptr<SkJpegMultiPictureParameters> Make(
const sk_sp<const SkData>& segmentParameters);
* Serialize Jpeg Multi-Picture Format segment parameters for the indicated individual image.
* This segment will start with the {'M', 'P', 'F', 0} signature (it will not include the
* segment marker or parameter length).
sk_sp<SkData> serialize(uint32_t individualImageNumber) const;
* Compute the absolute offset (from the start of the image) for the offset in the multi-picture
* parameters, given the absolute offset of the MPF segment (the offset of the {0xFF, 0xE2}
* marker from the start of the image.
static size_t GetImageAbsoluteOffset(uint32_t dataOffset, size_t mpSegmentOffset);
* Compute the data offset (as stored in the multi-picture params) for an image given its
* absolute offset (from the start of the first individual image), and the absolute offset
* of the MPF segment in the first individual image. This will return 0 for an image at
* absolute offset 0.
static uint32_t GetImageDataOffset(size_t imageAbsoluteOffset, size_t mpSegmentOffset);