如何获取原始 jpeg 数据（但没有元标记/专有标记）

Question

我想获取原始 jpeg 数据 - 没有元数据。 我对 jpeg“标准”感到非常困惑。

我对标记“树”的理解有多正确？

0xFFD8 - Identifies the file as an image
    0xFFE? - EXIF, JFIF, SPIFF, ICC, etc 
        0x???? - the length of the tag
    0xFFD8 - Start of Image
        0xFFE0 - should follow SOI as per spec, but often preceded by comments ???
        0x???? - Matrices, tags, random data ???

        There are never other markers in-between these markers? 
        Or these include the matrices and such?
        0xFFDA - Start of Stream - This is what I want, yes?
            0xXXXX - length of stream
            0xFFD9 - End of Stream (EOI)

        0x???? - Comment tags, extra exif, jfif info???
0xFFD9 - End of Image

0xFF00 - escaped 0xFF, not to be confused with a marker

这是我的阅读材料：

http://en.wikipedia.org/wiki/JPEG

https://ExifTool.org/TagNames/JPEG.html

http://www.media.mit.edu/pia/Research/deepview/exif.html

http://www.faqs.org/faqs/ jpeg-faq/part1/section-15.html

Answer 1

除了 SOS (0xFFDA)，您可能还需要以下内容：

0xFFDB DQT 量化表
0xFFC4 DHT定义哈夫曼表

Answer 2

有一个相当合理的“JPEG 剖析” 这里< /a> 向您展示如何使用 grep 从 JPEG 文件中提取 JPEG 标记和部分，例如 SOF 标记：

xxd -c16 -g1 -u testimg.jpg | grep --color=always -C2 "FF C0"
0000090: 32 32 32 32 32 32 32 32 32 32 32 32 32 32 FF C0  22222222222222..
00000a0: 00 11 08 00 95 00 E3 03 01 22 00 02 11 01 03 11  ........."......
00000b0: 01 FF C4 00 1F 00 00 01 05 01 01 01 01 01 01 00  ................

解释

0xFF, 0xC0,             // SOF0 segement
0x00, 0x11,             // length of segment depends on the number of components
0x08,                   // bits per pixel
0x00, 0x95,             // image height
0x00, 0xE3,             // image width
0x03,                   // number of components (should be 1 or 3)
0x01, 0x22, 0x00,       // 0x01=Y component, 0x22=sampling factor, quantization table number
0x02, 0x11, 0x01,       // 0x02=Cb component, ...
0x03, 0x11, 0x01        // 0x03=Cr component, ...

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并且有一个此处的完整、高度详细和全面的视频系列 < strong>YouTube 可以告诉您有关 JPEG 的更多信息，超出您的想象。

---

另请注意，您可以使用 exiftool 提取并检查文件中的 JPEG 标记，如下所示：

exiftool -v -v -v image.jpg

示例输出

  ExifToolVersion = 12.00
  FileName = iphone.jpg
  Directory = .
  FileSize = 2219100
  FileModifyDate = 1596126733
  FileAccessDate = 1610564128
  FileInodeChangeDate = 1596126733
  FilePermissions = 33188
  FileType = JPEG
  FileTypeExtension = JPG
  MIMEType = image/jpeg
JPEG APP1 (12284 bytes):
    0006: 45 78 69 66 00 00 4d 4d 00 2a 00 00 00 08 00 0b [Exif..MM.*......]
    0016: 01 0f 00 02 00 00 00 06 00 00 00 92 01 10 00 02 [................]
    0026: 00 00 00 09 00 00 00 98 01 12 00 03 00 00 00 01 [................]
    0036: 00 01 00 00 01 1a 00 05 00 00 00 01 00 00 00 a2 [................]
    0046: 01 1b 00 05 00 00 00 01 00 00 00 aa 01 28 00 03 [.............(..]
    0056: 00 00 00 01 00 02 00 00 01 31 00 02 00 00 00 06 [.........1......]
    0066: 00 00 00 b2 01 32 00 02 00 00 00 14 00 00 00 b8 [.....2..........]
    [snip 12172 bytes]
  ExifByteOrder = MM
  + [IFD0 directory with 11 entries]
  | 0)  Make = Apple
  |     - Tag 0x010f (6 bytes, string[6]):
  |         009e: 41 70 70 6c 65 00                               [Apple.]
  | 1)  Model = iPhone 4
  |     - Tag 0x0110 (9 bytes, string[9]):
  |         00a4: 69 50 68 6f 6e 65 20 34 00                      [iPhone 4.]
  | 2)  Orientation = 1
  |     - Tag 0x0112 (2 bytes, int16u[1]):
  |         0036: 00 01                                           [..]
  | 3)  XResolution = 72 (72/1)
  |     - Tag 0x011a (8 bytes, rational64u[1]):
  |         00ae: 00 00 00 48 00 00 00 01                         [...H....]
  | 4)  YResolution = 72 (72/1)
  |     - Tag 0x011b (8 bytes, rational64u[1]):
  |         00b6: 00 00 00 48 00 00 00 01                         [...H....]
  | 5)  ResolutionUnit = 2
  |     - Tag 0x0128 (2 bytes, int16u[1]):
  |         005a: 00 02                                           [..]
  | 6)  Software = 6.1.2
  |     - Tag 0x0131 (6 bytes, string[6]):
  |         00be: 36 2e 31 2e 32 00                               [6.1.2.]
  | 7)  ModifyDate = 2013:03:09 08:59:50
  |     - Tag 0x0132 (20 bytes, string[20]):
  |         00c4: 32 30 31 33 3a 30 33 3a 30 39 20 30 38 3a 35 39 [2013:03:09 08:59]
  |         00d4: 3a 35 30 00                                     [:50.]
  | 8)  YCbCrPositioning = 1
  |     - Tag 0x0213 (2 bytes, int16u[1]):
  |         007e: 00 01                                           [..]
  | 9)  ExifOffset (SubDirectory) -->
  |     - Tag 0x8769 (4 bytes, int32u[1]):
  |         008a: 00 00 00 cc                                     [....]
  | + [ExifIFD directory with 24 entries]
  | | 0)  ExposureTime = 0.001094091904 (1/914)
  | |     - Tag 0x829a (8 bytes, rational64u[1]):
  | |         01fe: 00 00 00 01 00 00 03 92                         [........]
  | | 1)  FNumber = 2.8 (14/5)
  | |     - Tag 0x829d (8 bytes, rational64u[1]):
  | |         0206: 00 00 00 0e 00 00 00 05                         [........]
  | | 2)  ExposureProgram = 2
  | |     - Tag 0x8822 (2 bytes, int16u[1]):
  | |         00fa: 00 02                                           [..]
  | | 3)  ISO = 80
  | |     - Tag 0x8827 (2 bytes, int16u[1]):
  | |         0106: 00 50                                           [.P]
  | | 4)  ExifVersion = 0221
  | |     - Tag 0x9000 (4 bytes, undef[4]):
  | |         0112: 30 32 32 31                                     [0221]
  | | 5)  DateTimeOriginal = 2013:03:09 08:59:50
  | |     - Tag 0x9003 (20 bytes, string[20]):
  | |         020e: 32 30 31 33 3a 30 33 3a 30 39 20 30 38 3a 35 39 [2013:03:09 08:59]
  | |         021e: 3a 35 30 00                                     [:50.]
  | | 6)  CreateDate = 2013:03:09 08:59:50
  | |     - Tag 0x9004 (20 bytes, string[20]):
  | |         0222: 32 30 31 33 3a 30 33 3a 30 39 20 30 38 3a 35 39 [2013:03:09 08:59]
  | |         0232: 3a 35 30 00                                     [:50.]
  | | 7)  ComponentsConfiguration = 1 2 3 0
  | |     - Tag 0x9101 (4 bytes, undef[4] read as int8u[4]):
  | |         0136: 01 02 03 00                                     [....]
  | | 8)  ShutterSpeedValue = 9.83619211 (11469/1166)
  | |     - Tag 0x9201 (8 bytes, rational64s[1]):
  | |         0236: 00 00 2c cd 00 00 04 8e                         [..,.....]
  | | 9)  ApertureValue = 2.970853574 (4281/1441)
  | |     - Tag 0x9202 (8 bytes, rational64u[1]):
  | |         023e: 00 00 10 b9 00 00 05 a1                         [........]
  | | 10) BrightnessValue = 8.880310458 (21739/2448)
  | |     - Tag 0x9203 (8 bytes, rational64s[1]):
  | |         0246: 00 00 54 eb 00 00 09 90                         [..T.....]
  | | 11) MeteringMode = 5
  | |     - Tag 0x9207 (2 bytes, int16u[1]):
  | |         0166: 00 05                                           [..]
  | | 12) Flash = 0
  | |     - Tag 0x9209 (2 bytes, int16u[1]):
  | |         0172: 00 00                                           [..]
  | | 13) FocalLength = 3.85 (77/20)
  | |     - Tag 0x920a (8 bytes, rational64u[1]):
  | |         024e: 00 00 00 4d 00 00 00 14                         [...M....]
  | | 14) FlashpixVersion = 0100
  | |     - Tag 0xa000 (4 bytes, undef[4]):
  | |         018a: 30 31 30 30                                     [0100]
  | | 15) ColorSpace = 1
  | |     - Tag 0xa001 (2 bytes, int16u[1]):
  | |         0196: 00 01                                           [..]
  | | 16) ExifImageWidth = 2592
  | |     - Tag 0xa002 (4 bytes, int32u[1]):
  | |         01a2: 00 00 0a 20                                     [... ]
  | | 17) ExifImageHeight = 1936
  | |     - Tag 0xa003 (4 bytes, int32u[1]):
  | |         01ae: 00 00 07 90                                     [....]
  | | 18) SensingMethod = 2
  | |     - Tag 0xa217 (2 bytes, int16u[1]):
  | |         01ba: 00 02                                           [..]
  | | 19) CustomRendered = 2
  | |     - Tag 0xa401 (2 bytes, int16u[1]):
  | |         01c6: 00 02                                           [..]
  | | 20) ExposureMode = 0
  | |     - Tag 0xa402 (2 bytes, int16u[1]):
  | |         01d2: 00 00                                           [..]
  | | 21) WhiteBalance = 0
  | |     - Tag 0xa403 (2 bytes, int16u[1]):
  | |         01de: 00 00                                           [..]
  | | 22) FocalLengthIn35mmFormat = 35
  | |     - Tag 0xa405 (2 bytes, int16u[1]):
  | |         01ea: 00 23                                           [.#]
  | | 23) SceneCaptureType = 0
  | |     - Tag 0xa406 (2 bytes, int16u[1]):
  | |         01f6: 00 00                                           [..]
  | 10) GPSInfo (SubDirectory) -->
  |     - Tag 0x8825 (4 bytes, int32u[1]):
  |         0096: 00 00 02 4a                                     [...J]
  | + [GPS directory with 9 entries]
  | | 0)  GPSLatitudeRef = N
  | |     - Tag 0x0001 (2 bytes, string[2]):
  | |         0260: 4e 00                                           [N.]
  | | 1)  GPSLatitude = 20 50.66 0 (20/1 5066/100 0/1)
  | |     - Tag 0x0002 (24 bytes, rational64u[3]):
  | |         02c8: 00 00 00 14 00 00 00 01 00 00 13 ca 00 00 00 64 [...............d]
  | |         02d8: 00 00 00 00 00 00 00 01                         [........]
  | | 2)  GPSLongitudeRef = E
  | |     - Tag 0x0003 (2 bytes, string[2]):
  | |         0278: 45 00                                           [E.]
  | | 3)  GPSLongitude = 107 5.46 0 (107/1 546/100 0/1)
  | |     - Tag 0x0004 (24 bytes, rational64u[3]):
  | |         02e0: 00 00 00 6b 00 00 00 01 00 00 02 22 00 00 00 64 [...k......."...d]
  | |         02f0: 00 00 00 00 00 00 00 01                         [........]
  | | 4)  GPSAltitudeRef = 0
  | |     - Tag 0x0005 (1 bytes, int8u[1]):
  | |         0290: 00                                              [.]
  | | 5)  GPSAltitude = 1.12868102 (4561/4041)
  | |     - Tag 0x0006 (8 bytes, rational64u[1]):
  | |         02f8: 00 00 11 d1 00 00 0f c9                         [........]
  | | 6)  GPSTimeStamp = 1 59 48.81 (1/1 59/1 4881/100)
  | |     - Tag 0x0007 (24 bytes, rational64u[3]):
  | |         0300: 00 00 00 01 00 00 00 01 00 00 00 3b 00 00 00 01 [...........;....]
  | |         0310: 00 00 13 11 00 00 00 64                         [.......d]
  | | 7)  GPSImgDirectionRef = T
  | |     - Tag 0x0010 (2 bytes, string[2]):
  | |         02b4: 54 00                                           [T.]
  | | 8)  GPSImgDirection = 324.4435484 (40231/124)
  | |     - Tag 0x0011 (8 bytes, rational64u[1]):
  | |         0318: 00 00 9d 27 00 00 00 7c                         [...'...|]
  + [IFD1 directory with 6 entries]
  | 0)  Compression = 6
  |     - Tag 0x0103 (2 bytes, int16u[1]):
  |         032a: 00 06                                           [..]
  | 1)  XResolution = 72 (72/1)
  |     - Tag 0x011a (8 bytes, rational64u[1]):
  |         036e: 00 00 00 48 00 00 00 01                         [...H....]
  | 2)  YResolution = 72 (72/1)
  |     - Tag 0x011b (8 bytes, rational64u[1]):
  |         0376: 00 00 00 48 00 00 00 01                         [...H....]
  | 3)  ResolutionUnit = 2
  |     - Tag 0x0128 (2 bytes, int16u[1]):
  |         034e: 00 02                                           [..]
  | 4)  ThumbnailOffset = 882
  |     - Tag 0x0201 (4 bytes, int32u[1]):
  |         035a: 00 00 03 72                                     [...r]
  | 5)  ThumbnailLength = 7847
  |     - Tag 0x0202 (4 bytes, int32u[1]):
  |         0366: 00 00 1e a7                                     [....]
JPEG DQT (130 bytes):
    3006: 00 01 01 01 01 01 01 01 01 01 01 01 01 01 01 02 [................]
    3016: 04 02 02 02 02 02 04 03 03 02 04 05 05 06 06 05 [................]
    3026: 05 05 05 06 07 09 07 06 06 08 06 05 05 08 0a 08 [................]
    3036: 08 09 09 0a 0a 0a 06 07 0b 0c 0b 0a 0c 09 0a 0a [................]
    3046: 09 01 01 01 01 02 02 02 04 02 02 04 09 06 05 06 [................]
    3056: 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 [................]
    3066: 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 09 [................]
    [snip 18 bytes]
JPEG SOF0 (15 bytes):
    308c: 08 07 90 0a 20 03 01 22 00 02 11 01 03 11 01    [.... ..".......]
  ImageWidth = 2592
  ImageHeight = 1936
  EncodingProcess = 0
  BitsPerSample = 8
  ColorComponents = 3
  YCbCrSubSampling = 2 2
JPEG DHT (416 bytes):
    309f: 00 00 01 05 01 01 01 01 01 01 00 00 00 00 00 00 [................]
    30af: 00 00 01 02 03 04 05 06 07 08 09 0a 0b 10 00 02 [................]
    30bf: 01 03 03 02 04 03 05 05 04 04 00 00 01 7d 01 02 [.............}..]
    30cf: 03 00 04 11 05 12 21 31 41 06 13 51 61 07 22 71 [......!1A..Qa."q]
    30df: 14 32 81 91 a1 08 23 42 b1 c1 15 52 d1 f0 24 33 [.2....#B...R..$3]
    30ef: 62 72 82 09 0a 16 17 18 19 1a 25 26 27 28 29 2a [br........%&'()*]
    30ff: 34 35 36 37 38 39 3a 43 44 45 46 47 48 49 4a 53 [456789:CDEFGHIJS]
    [snip 304 bytes]
JPEG SOS
JPEG EOI

关键字：JPEG、标记、解剖学、SOF、DQT、DHT、素数。