1 /* 2 * Copyright 2023 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkJpegMultiPicture_codec_DEFINED 9 #define SkJpegMultiPicture_codec_DEFINED 10 11 #include "include/core/SkRefCnt.h" 12 13 #include <cstdint> 14 #include <memory> 15 #include <vector> 16 17 class SkData; 18 19 /* 20 * Parsed Jpeg Multi-Picture Format structure as specified in CIPA DC-x007-2009. An introduction to 21 * the format can be found in Figure 1 (Basic MP File format data structure) and Figure 6 (Internal 22 * Structure of the MP Index IFD) in that document. This parsing will extract only the size and 23 * offset parameters from the images in the Index Image File Directory. 24 */ 25 struct SkJpegMultiPictureParameters { 26 // An individual image. 27 struct Image { 28 // The size of the image in bytes. 29 uint32_t size = 0; 30 // The offset of the image in bytes. This offset is specified relative to the address of 31 // the MP Endian field in the MP Header, unless the image is a First Individual Image, in 32 // which case the value of the offest [sic] shall be NULL (from section 5.2.3.3). 33 uint32_t dataOffset = 0; 34 }; 35 36 // The images listed in the Index Image File Directory. 37 std::vector<Image> images; 38 39 /* 40 * Parse Jpeg Multi-Picture Format parameters. The specified data should be APP2 segment 41 * parameters, which, if they are MPF parameter, should start with the {'M', 'P', 'F', 0} 42 * signature. Returns nullptr the parameters do not start with the MPF signature, or if there 43 * is an error in parsing the parameters. 44 */ 45 static std::unique_ptr<SkJpegMultiPictureParameters> Make( 46 const sk_sp<const SkData>& segmentParameters); 47 48 /* 49 * Serialize Jpeg Multi-Picture Format parameters into a segment. This segment will start with 50 * the {'M', 'P', 'F', 0} signature (it will not include the segment marker or parameter 51 * length). 52 */ 53 sk_sp<SkData> serialize() const; 54 55 /* 56 * Compute the absolute offset (from the start of the image) for the offset in the multi-picture 57 * parameters, given the absolute offset of the MPF segment (the offset of the {0xFF, 0xE2} 58 * marker from the start of the image. 59 */ 60 static size_t GetAbsoluteOffset(uint32_t dataOffset, size_t mpSegmentOffset); 61 }; 62 63 #endif 64