Writing an image

[Mr. Costington]

Hi all, I was trying to hava a CGI script return an image, but it was coming
back corrupted. So I tried this simple non-CGI test and still get errors:

import sys
image = open('pic.jpg','rb').read()
sys.stdout.write(image)

When I run this like "python pic.py > pic2.jpg"
The resulting pic2.jpg is not identical to the original. I looked at it in
a hex editor, and it seems to be identical with the original pic.jpg, except
for several 0D (carraige return) characters inserted throughout the file.

I tried this with Python 2.2.1 and 2.3.2. What's going on?
Thanks in advance,
-Noah

 

[Michael Hudson]

Hi all, I was trying to hava a CGI script return an image, but it was coming
back corrupted. So I tried this simple non-CGI test and still get errors:

import sys
image = open('pic.jpg','rb').read()
sys.stdout.write(image)

When I run this like "python pic.py > pic2.jpg"
The resulting pic2.jpg is not identical to the original. I looked at it in
a hex editor, and it seems to be identical with the original pic.jpg, except
for several 0D (carraige return) characters inserted throughout the file.

sys.stdout is not usually a binary-mode file.

Cheers,
mwh

 

[Werner Schiendl]

Hi,

When I run this like "python pic.py > pic2.jpg"
The resulting pic2.jpg is not identical to the original. I looked at it in
a hex editor, and it seems to be identical with the original pic.jpg, except
for several 0D (carraige return) characters inserted throughout the file.

I tried this with Python 2.2.1 and 2.3.2. What's going on?

The sys.stdout is obviously open in text (not binary) mode.

When you write "\n" (linefeed) you'll get "\r\n" (carriage return +
linefeed) in the destination.

hth

Werner

 

[Alex Martelli]

...
sys.stdout is not usually a binary-mode file.

Right; one can change that with the -u switch to python (e.g., starting
the cgi script with
#!c:\python23\python.exe -u
if one's webserver recognizes and applies hashbang conventions).


Alex

 

[Mr. Costington]

Right; one can change that with the -u switch to python (e.g., starting
the cgi script with
#!c:\python23\python.exe -u
if one's webserver recognizes and applies hashbang conventions).

Thanks. My server ignores hashbangs, but I was able to set sys.stdout to
binary-mode with the following line:
msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)