Python .JPEG Recognition

Question

I was trying to write a program that would grab the ascii or binary behind a .jpeg and find for example the "JFIFHH" to verify thats its really a JPEG the simple script i wrote was

    test = open('test.jpeg', 'rb')

data = test.read()
print(data)

if 'JFIFHH' in data :
    print('FOUND')

elif 'JFIFHH' not in data :     
  print('not found')

It always prints not found even if its there. so i found out it wasn't the binary it printed but something else, so how can i make this work???

are you sure of your pattern? `JFIF` is probably found but not sure of the `HH` part — Jean-François Fabre, Nov 04 '17 at 17:58
also this is the wrong way: https://stackoverflow.com/questions/4550296/how-to-identify-contents-of-a-byte-is-a-jpeg — Jean-François Fabre, Nov 04 '17 at 18:15

Jean-François Fabre · Accepted Answer · 2017-11-04T18:18:39.433

0

This isn't the proper pattern to look for in the first place. I checked a JPEG file and it contained JFIF but not JFIFHH...

As this answer states you should look for FF D8 start & FF D9 end byte sequences, like this (Python 2/3 compatible code):

with open("test.jpeg","rb") as f:
    contents = f.read()
    if contents.startswith(b"\xff\xd8") and contents.endswith(b"\xff\xd9"):
        print("it's a jpeg")

edited Nov 04 '17 at 18:18

answered Nov 04 '17 at 17:54

Jean-François Fabre

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Python .JPEG Recognition

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