Writing byte stream as jpeg format to disk

MRAB python at mrabarnett.plus.com
Thu Aug 26 23:18:26 CEST 2010


On 26/08/2010 21:47, Navkirat Singh wrote:
>
> On 27-Aug-2010, at 1:57 AM, MRAB wrote:
>
>> On 26/08/2010 21:14, Navkirat Singh wrote:
>>>
>>> On 27-Aug-2010, at 1:32 AM, Dave Angel wrote:
>>>
>>>> Navkirat Singh wrote:
>>>>> Hey guys,
>>>>>
>>>>> I am programming a webserver, I receive a jpeg file with the POST
>>>>> method.The file (.jpeg) is encoded in bytes, I parse the bytes by
>>>>> decoding them to a string. I wanted to know how i could write the
>>>>> file (now a string) as a jpeg image on disk. When I try to encode the
>>>>> same string to a bytes and write them in binary format to disk, the
>>>>> file is not recognized as jpeg. I would be grateful if someone could
>>>>> help me with this.
>>>>>
>>>>>
>>>>> Regards,
>>>>> Nav
>>>> If by "decoding them to a string" you mean converting to Unicode, then
>>>> you've already trashed the data. That's only valid if the bytes had
>>>> been encoded from valid Unicode characters, and then only if you use
>>>> the corresponding decoding technique.
>>>>
>>>> If you mean some other decoding, then the question is meaningless
>>>> without telling us just what the decoding is, preferably with some code.
>>>>
>>>> It also might be useful to know what version of Python you're using,
>>>> when you post the code.
>>>>
>>>> DaveA
>>>>
>>>
>>> Dave,
>>>
>>> I am using Python3 and I receive a byte stream with a jpeg attached sent
>>> by the web browser over a socket, which looks like this:
>>>
>>> b': image/jpeg\r\nAccept: text/*\r\nReferer:
>>> http://127.0.0.1:8001/\r\nAccept-Language: en-us\r\nAccept-Encoding:
>>> gzip, deflate\r\nContent-Length: 91783\r\nConnection:
>>> keep-alive\r\n\r\n\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00\x84\x00\x03\x02\x02\x03\x02\x02\x03\x03\x03\x03\x04\x03\x03\x04\x05\x08\x05\x05\x04\x04\x05\n\x07\x07\x06\x08\x0c\n\x0c\x0c\x0b\n\x0b\x0b\r\x0e\x12\x10\r\x0e\x11\x0e\x0b\x0b\x10\x16\x10\x11\x13\x14\x15\x15\x15\x0c\x0f
>>>
>>>  From the above, I need to:
>>>
>>> a) Split the header content from the image content, which comes after
>>> the keep-alive\r\n\r\n part
>>>
>>> b) Then write the image content to file for further use as a jpeg.
>>>
>> Try:
>>
>>     image = header.split(b'keep-alive\r\n\r\n', 1)[-1]
>>     open(image_path, 'wb').write(image)
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>
> I think I forgot to mention that the original is a stream of bytes decoded using ISO-8859-1 as utf-8 trhrew errors (lack of knowlegdge again).
>
> @MRAB - the split() method in python 3 works only on strings and throws an error if I try to use bytes
>
All i can say is that it works for me:

 >>> header = b': image/jpeg\r\nAccept: text/*\r\nReferer: 
http://127.0.0.1:8001/\r\nAccept-Language:  en-us\r\nAccept-Encoding: 
gzip, deflate\r\nContent-Length: 91783\r\nConnection: 
keep-alive\r\n\r\n\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00\x84\x00\x03\x02\x02\x03\x02\x02\x03\x03\x03\x03\x04\x03\x03\x04\x05\x08\x05\x05\x04\x04\x05\n\x07\x07\x06\x08\x0c\n\x0c\x0c\x0b\n\x0b\x0b\r\x0e\x12\x10\r\x0e\x11\x0e\x0b\x0b\x10\x16\x10\x11\x13\x14\x15\x15\x15\x0c\x0f'
 >>> image = header.split(b'keep-alive\r\n\r\n', 1)[-1]
 >>> image
b'\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xdb\x00\x84\x00\x03\x02\x02\x03\x02\x02\x03\x03\x03\x03\x04\x03\x03\x04\x05\x08\x05\x05\x04\x04\x05\n\x07\x07\x06\x08\x0c\n\x0c\x0c\x0b\n\x0b\x0b\r\x0e\x12\x10\r\x0e\x11\x0e\x0b\x0b\x10\x16\x10\x11\x13\x14\x15\x15\x15\x0c\x0f'

What error did you get?



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