Here's the source, together with the compiled binary and a sample image from Wikipedia: 200510-uncode-jpeg.tgz (ca. 100 kB) 200527-uncode-jpeg.tgz (ca. 110 kB)
There are lots of unsupported JPEG markers. In the new version (27th of Mai) Table indices are handled correctly. In the new version you can write a stripped version of the file with -o NEWFILE.jpg. (Works only with few files.)
This tool helps with getting an overview over a arbitrary JPEG file.
The program output looks like this:
Opening file Bilder/SDC16414x.jpg .
Marker 1 @0x 0 +1 : SOI Start Of Image
Marker 2 @0x 2 -> 0x 1dd7: APPn Application-specific (1 - EXIF/XMP)
EXIF metadata
interoperability number = hex 0B 00
Scanning through additional 7617 bytes which are non-consumed yet ...
Marker 2a @0x f8c +1 : SOI Start Of Image
Marker 2b @0x f8e -> 0x 1014: DQT Define Quantization Table(s) q0, 64x1 B
q1, 64x1 B
Marker 2c @0x 1014 -> 0x 11b8: DHT Define Huffman Table(s) ID 00, #cp: 12
ID 01, #cp: 12
ID 10, #cp: 162
ID 11, #cp: 162
Marker 2d @0x 11b8 -> 0x 11cb: SOF0 Start Of Frame (0 - baseline DCT)
prec 8, size 160 x 120, component 1: sampling fact. 0x21, table q0
component 2: sampling fact. 0x11, table q1
component 3: sampling fact. 0x11, table q1
Marker 2e @0x 11cb -> 0x 11d9: SOS Start Of Scan
component 1: huffman tables: ID 00 DC, ID 10 AC
component 2: huffman tables: ID 01 DC, ID 11 AC
component 3: huffman tables: ID 01 DC, ID 11 AC
further flags: 0x00 0x3f 0x00
Marker 2f @0x 1dd5 +1 : EOI End Of Image
... scanning done
Marker 3 @0x 1dd7 +1 : invalid - ffe3 was not exptected here
Marker 4 @0x 1dd9 +1 : invalid - ffff was not exptected here
Marker 5 @0x 1ddb +1 : SOI Start Of Image
Marker 6 @0x 1ddd -> 0x 1e63: DQT Define Quantization Table(s) q0, 64x1 B
q1, 64x1 B
Marker 7 @0x 1e63 -> 0x 2007: DHT Define Huffman Table(s) ID 00, #cp: 12
ID 01, #cp: 12
ID 10, #cp: 162
ID 11, #cp: 162
Marker 8 @0x 2007 -> 0x 201a: SOF0 Start Of Frame (0 - baseline DCT)
prec 8, size 640 x 480, component 1: sampling fact. 0x21, table q0
component 2: sampling fact. 0x11, table q1
component 3: sampling fact. 0x11, table q1
Marker 9 @0x 201a -> 0x 2028: SOS Start Of Scan
component 1: huffman tables: ID 00 DC, ID 10 AC
component 2: huffman tables: ID 01 DC, ID 11 AC
component 3: huffman tables: ID 01 DC, ID 11 AC
further flags: 0x00 0x3f 0x00
Marker 10 @0x 11dd8 +1 : invalid - ffe4 was not exptected here
Marker 11 @0x 1ab5d +1 : EOI End Of Image
Marker 12 @0x 1ab5f -> 0x 1abe5: DQT Define Quantization Table(s) q0, 64x1 B
q1, 64x1 B
Marker 13 @0x 1abe5 -> 0x 1ad89: DHT Define Huffman Table(s) ID 00, #cp: 12
ID 01, #cp: 12
ID 10, #cp: 162
ID 11, #cp: 162
Marker 14 @0x 1ad89 -> 0x 1ad9c: SOF0 Start Of Frame (0 - baseline DCT)
prec 8, size 3648 x 2736, component 1: sampling fact. 0x21, table q0
component 2: sampling fact. 0x11, table q1
component 3: sampling fact. 0x11, table q1
Marker 15 @0x 1ad9c -> 0x 1adaa: SOS Start Of Scan
component 1: huffman tables: ID 00 DC, ID 10 AC
component 2: huffman tables: ID 01 DC, ID 11 AC
component 3: huffman tables: ID 01 DC, ID 11 AC
further flags: 0x00 0x3f 0x00
Marker 16 @0x2a0e7f +1 : EOI End Of Image
End of file reached.
Remark: this is not the sample file you find in archive!
This is a baseline jpeg file (on slow connections renders visibly from top to bottom). In contrast, a progressive jpeg file would be blurred in the beginning and get sharper till the end of the transmission.
You can delete all contents of markers 2-11; marker 1+12-16 do contain the actual image.
After invoking exiftool -APP3:all= -EXIF:all= -APP4:all= SDC16414x.jpg the
file looks like this (and is more than 5% smaller):
Opening file SDC16414x.jpg .
Marker 1 @0x 0 +1 : SOI Start Of Image
Marker 2 @0x 2 -> 0x 88: DQT Define Quantization Table(s) q0, 64x1 B
q1, 64x1 B
Marker 3 @0x 88 -> 0x 22c: DHT Define Huffman Table(s) ID 00, #cp: 12
ID 01, #cp: 12
ID 10, #cp: 162
ID 11, #cp: 162
Marker 4 @0x 22c -> 0x 23f: SOF0 Start Of Frame (0 - baseline DCT)
prec 8, size 3648 x 2736, component 1: sampling fact. 0x21, table q0
component 2: sampling fact. 0x11, table q1
component 3: sampling fact. 0x11, table q1
Marker 5 @0x 23f -> 0x 24d: SOS Start Of Scan
component 1: huffman tables: ID 00 DC, ID 10 AC
component 2: huffman tables: ID 01 DC, ID 11 AC
component 3: huffman tables: ID 01 DC, ID 11 AC
further flags: 0x00 0x3f 0x00
Marker 6 @0x286322 +1 : EOI End Of Image
End of file reached.