1 /* 2 * Copyright 2023 Google LLC 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 SkJpegConstants_codec_DEFINED 9 #define SkJpegConstants_codec_DEFINED 10 11 #include <cstddef> 12 #include <cstdint> 13 14 // The first marker of all JPEG files is StartOfImage. 15 static constexpr uint8_t kJpegMarkerStartOfImage = 0xD8; 16 17 // The last marker of all JPEG files (excluding auxiliary data, e.g, MPF images) is EndOfImage. 18 static constexpr uint8_t kJpegMarkerEndOfImage = 0xD9; 19 20 // The header of a JPEG file is the data in all segments before the first StartOfScan. 21 static constexpr uint8_t kJpegMarkerStartOfScan = 0xDA; 22 23 // Metadata and auxiliary images are stored in the APP1 through APP15 markers. 24 static constexpr uint8_t kJpegMarkerAPP0 = 0xE0; 25 26 // The number of bytes in a marker code is two. The first byte is all marker codes is 0xFF. 27 static constexpr size_t kJpegMarkerCodeSize = 2; 28 29 // The number of bytes used to specify the length of a segment's parameters is two. This length 30 // value includes these two bytes. 31 static constexpr size_t kJpegSegmentParameterLengthSize = 2; 32 33 // The first three bytes of all JPEG files is a StartOfImage marker (two bytes) followed by the 34 // first byte of the next marker. 35 static constexpr uint8_t kJpegSig[] = {0xFF, kJpegMarkerStartOfImage, 0xFF}; 36 37 // ICC profile segment marker and signature. 38 static constexpr uint32_t kICCMarker = kJpegMarkerAPP0 + 2; 39 static constexpr uint32_t kICCMarkerHeaderSize = 14; 40 static constexpr uint32_t kICCMarkerIndexSize = 1; 41 static constexpr uint8_t kICCSig[] = { 42 'I', 'C', 'C', '_', 'P', 'R', 'O', 'F', 'I', 'L', 'E', '\0', 43 }; 44 45 // XMP segment marker and signature. 46 static constexpr uint32_t kXMPMarker = kJpegMarkerAPP0 + 1; 47 static constexpr uint8_t kXMPStandardSig[] = { 48 'h', 't', 't', 'p', ':', '/', '/', 'n', 's', '.', 'a', 'd', 'o', 'b', 'e', '.', 'c', 'o', 49 'm', '/', 'x', 'a', 'p', '/', '1', '.', '0', '/', '\0'}; 50 static constexpr uint8_t kXMPExtendedSig[] = { 51 'h', 't', 't', 'p', ':', '/', '/', 'n', 's', '.', 'a', 'd', 'o', 'b', 'e', '.', 'c', 'o', 52 'm', '/', 'x', 'm', 'p', '/', 'e', 'x', 't', 'e', 'n', 's', 'i', 'o', 'n', '/', '\0'}; 53 54 // EXIF segment marker and signature. 55 static constexpr uint32_t kExifMarker = kJpegMarkerAPP0 + 1; 56 constexpr uint8_t kExifSig[] = {'E', 'x', 'i', 'f', '\0'}; 57 58 // MPF segment marker and signature. 59 static constexpr uint32_t kMpfMarker = kJpegMarkerAPP0 + 2; 60 static constexpr uint8_t kMpfSig[] = {'M', 'P', 'F', '\0'}; 61 62 // ISO 21496-1 marker and signature. 63 static constexpr uint32_t kISOGainmapMarker = kJpegMarkerAPP0 + 2; 64 static constexpr uint8_t kISOGainmapSig[] = {'u', 'r', 'n', ':', 'i', 's', 'o', ':', 's', 't', 65 'd', ':', 'i', 's', 'o', ':', 't', 's', ':', '2', 66 '1', '4', '9', '6', ':', '-', '1', '\0'}; 67 68 #endif 69