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I'm having problem with parsing jpeg file. When I hit SOS (start of scan) marker, there are few bytes which meaning I don't understand. In picture bellow, after SOS marker, there are 2 bytes for header length (Ls part on the picture). But what the rest of data on picture mean (for example Ns, Cs1 etc....), and where the pure data starts?
947
Solution 1: Open the image in MsPaint! then save it back over the original file or save as a new jpeg/png/bitmap/tiff file. Open the new image in photoshop. Solution 2: If you have large number of images then the first solution will be time consuming.
The SOS marker contains the compressed data; the most complex part of the JPEG stream. The SOFn marker indicates the format of the data. SOF0 and SOF1 are processed identically. SOF2 (progressive) is quite a bit different. (The read of the SOFn markers are not in common use or commonly supported).
Go to File > Save as and open the Save as type drop-down menu. You can then select JPEG and PNG, as well as TIFF, GIF, HEIC, and multiple bitmap formats. Save the file to your computer and it will convert.
Cs1 is a components selection index, This refers back to the SOF section (where horizontal and vertical sampling factors are specified)
Td1 is the DC table selector for the current component (Cs1)
Ta1 is the AC table selector for the current component (Cs1)
Ss, Se and Ah,Al define the spectral selection for the current scan data (this is used in progressive bitmaps. In the first round of rendering, only lower frequencies are shown, in the final round, more detailed frequencies are shown)
The scan data starts after Al
In summary,
SOS (2 bytes)
Ls (2 Bytes)
Ns (1 byte)
Component Specific Parameters (Ns * 2 bytes)
Ss (1 byte)
Se (1 byte)
Ah,AL (1 byte)
... scan data ...
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