问题
I'm extracting jpeg type bits from mp3 data actually it will be album arts. I thought about using library called mutagen, but I'd like to try with bits for some practice purpose.
import os
import sys
import re
f = open(sys.argv[1], "rb")
#sys.argv[1] gets mp3 file name ex) test1.mp3
saver = ""
for value in f:
for i in value:
hexval = hex(ord(i))[2:]
if (ord(i) == 0):
saver += "00" #to match with hex form
else:
saver += hexval
header = "ffd8"
tail = "ffd9"
this part of code is to get mp3 as bit form, and then transform it into hex and find jpeg trailers which starts as "ffd8" and ends with "ffd9"
frontmatch = re.search(header,saver)
endmatch = re.search(tail, saver)
startIndex = frontmatch.start()
endIndex = endmatch.end()
jpgcontents = saver[startIndex:endIndex]
scale = 16 # equals to hexadecimal
numbits = len(jpgcontents) * 4 #log2(scale)
bitcontents = bin(int(jpgcontents, scale))[2:].zfill(numbits)
and here, I get the bits between the header and tail and transform it into binary form. Which supposed to be the jpg part of the mp3 files.
txtfile = open(sys.argv[1] + "_tr.jpg", "w")
txtfile.write(bitcontents)
and I wrote the bin to the new file with writing type as jpg. sorry for my wrong naming as txtfile.
But these codes gave the error which is
Error interpreting JPEG image file
(Not a JPEG file: starts with 0x31 0x31)
I'm not sure whether the bits I extracted are wrong or writing to the file step is wrong. Or there might be other problem in code.
I'm working in linux version with python 2.6. Is there anything wrong with just writing str type of bin data as JPG?
回答1:
You are creating a string of ASCII zeroes and ones, i.e. \x30 and \x31, but the JPEG file needs to be proper binary data. So where your file should have a single byte of (for example) \xd8 you instead have these eight bytes: 11011000, or \x31\x31\x30\x31\x31\x30\x30\x30.
You don't need to do all that messy conversion stuff. You can just search directly for the desired byte patterns, writing them using \x hex escape sequences. And you don't even need regex: the simple string .index or .find methods can do this easily and quickly.
with open(fname, 'rb') as f:
data = f.read()
header = "\xff\xd8"
tail = "\xff\xd9"
try:
start = data.index(header)
end = data.index(tail, start) + 2
except ValueError:
print "Can't find JPEG data!"
exit()
print 'Start: %d End: %d Size: %d' % (start, end, end - start)
with open(fname + "_tr.jpg", 'wb') as f:
f.write(data[start:end])
(Tested on Python 2.6.6)
However, extracting embedded JPEG data like this isn't foolproof, since it's possible that those header and tail byte sequences exist in the MP3 sound data.
FWIW, a simpler way to translate binary data to hex strings and back is to use hexlify and unhexlify from the binascii module.
Here are some examples of doing these transformations, both with and without the binascii functions.
from binascii import hexlify, unhexlify
#Create a string of all possible byte values
allbytes = ''.join([chr(i) for i in xrange(256)])
print 'allbytes'
print repr(allbytes)
print '\nhex list'
print [hex(ord(v))[2:].zfill(2) for v in allbytes]
hexstr = hexlify(allbytes)
print '\nhex string'
print hexstr
newbytes = ''.join([chr(int(hexstr[i:i+2], 16)) for i in xrange(0, len(hexstr), 2)])
print '\nNew bytes'
print repr(newbytes)
print '\nUsing unhexlify'
print repr(unhexlify(hexstr))
output
allbytes
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
hex list
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '0a', '0b', '0c', '0d', '0e', '0f', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '1a', '1b', '1c', '1d', '1e', '1f', '20', '21', '22', '23', '24', '25', '26', '27', '28', '29', '2a', '2b', '2c', '2d', '2e', '2f', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '3a', '3b', '3c', '3d', '3e', '3f', '40', '41', '42', '43', '44', '45', '46', '47', '48', '49', '4a', '4b', '4c', '4d', '4e', '4f', '50', '51', '52', '53', '54', '55', '56', '57', '58', '59', '5a', '5b', '5c', '5d', '5e', '5f', '60', '61', '62', '63', '64', '65', '66', '67', '68', '69', '6a', '6b', '6c', '6d', '6e', '6f', '70', '71', '72', '73', '74', '75', '76', '77', '78', '79', '7a', '7b', '7c', '7d', '7e', '7f', '80', '81', '82', '83', '84', '85', '86', '87', '88', '89', '8a', '8b', '8c', '8d', '8e', '8f', '90', '91', '92', '93', '94', '95', '96', '97', '98', '99', '9a', '9b', '9c', '9d', '9e', '9f', 'a0', 'a1', 'a2', 'a3', 'a4', 'a5', 'a6', 'a7', 'a8', 'a9', 'aa', 'ab', 'ac', 'ad', 'ae', 'af', 'b0', 'b1', 'b2', 'b3', 'b4', 'b5', 'b6', 'b7', 'b8', 'b9', 'ba', 'bb', 'bc', 'bd', 'be', 'bf', 'c0', 'c1', 'c2', 'c3', 'c4', 'c5', 'c6', 'c7', 'c8', 'c9', 'ca', 'cb', 'cc', 'cd', 'ce', 'cf', 'd0', 'd1', 'd2', 'd3', 'd4', 'd5', 'd6', 'd7', 'd8', 'd9', 'da', 'db', 'dc', 'dd', 'de', 'df', 'e0', 'e1', 'e2', 'e3', 'e4', 'e5', 'e6', 'e7', 'e8', 'e9', 'ea', 'eb', 'ec', 'ed', 'ee', 'ef', 'f0', 'f1', 'f2', 'f3', 'f4', 'f5', 'f6', 'f7', 'f8', 'f9', 'fa', 'fb', 'fc', 'fd', 'fe', 'ff']
hex string
000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9fa0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff
New bytes
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
Using unhexlify
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
Note that this code needs some modifications to run on Python 3 (apart from converting the print statements to print function calls) because plain Python 3 strings are Unicode strings, not byte strings.
回答2:
You need to write out as binary
Try:
txtfile = open(sys.argv[1] + "_tr.jpg", "wb")
回答3:
Oups, you are not doing what you expect. the bin generates a string containing the value in binary form. Let's look at what you have, if the content on the input file was :
saveris a string of hexadecimal characters in textual form something like "313233414243" for an initial string of "132ABC"jpgcontentshas same format and starts with "ffd8" and ends with "ffd9"- you then apply the magic formula
bin(int(jpgcontents, scale))[2:].zfill(numbits)that- convert the hexa string to a long integer
- convert the long integer to a binary representation string - this part would convert hexa "ff" in integer 255 and end in the string "0b11111111"
- remove first characters "0b" and fill the end of buffer if needed
bitcontents is then a string starting with "11111111....". Just rename your file with a .txt extension and open it with a text editor, you will see that it is a large file containing only ASCII characters 0 and 1.
As the header is "ffd8" the file will start with 10 "1". So the error that it starts with 0x31 0x31 because 0x31 is the ascii code of "1".
What you need is convert the hexa string jpgcontents in a binary byte array.
fileimage = ''.join([ jpgcontent[i:i+2] for i in range(0, len(jpgcontent), 2]
You can then safely copy the fileimage buffer to a binary file:
file = open(sys.argv[1] + "_tr.jpg", "wb")
file.write(fileimage)
回答4:
The easiest method is using the binascii module: https://docs.python.org/2/library/binascii.html.
import binascii
# code in ascii format contained in a list
code = ['00', '01', '02', '03', '04', '05', '06', '07', '08', '09']
bfile = open('bfile.bin', 'w')
for c in code:
# convert the ascii to binary and write it to the file
bfile.write(binascii.unhexlify(c))
bfile.close()
来源：https://stackoverflow.com/questions/35748549/python-file-i-o-with-binary-data