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jpegjpeg2000

How to tell difference between JPEG and JPEG2000?

The question is: How can i tell two files apart? One coded with JPEG, another with JPEG2000.

I need format-specific file read/write functions, i can't find file encoding without reading it. JPEG works fine right now, but JPEG func fails to open JPEG2000. So i need to determine whether my file is JPG or JPEG2000.

Solution

  • According to the Digital Formats at Library of Congress, all JPEG 2000 files start with the following signature (also known as magic bytes or magic number):

    00 00 00 0C 6A 50 20 20 0D 0A 87 0A

    (The IANA record only lists the first 12, so I left the remainder out).

    Normal JPEG files on the other hand, starts with:

    FF D8 FF E0

    Comparing these bytes, you should easily be able to tell them apart.