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Sat Dec 27 12:49:46 EST 2003 · https://mail.python.org/pipermail/python-dev/2003-December/041435.html

[Sjoerd]
> >>I have some fixes for the imageop module to make it work on systems with 
> >>a different byte-order than IRIX (e.g. Linux).  Shall I check them in or 
> >>is it not worth it for such an old module?  Anything else that needs to 
> >>be changed when I check this in?
> >>The fixes of course will result in different results on Linux than 
> >>before, so that's the main reason for asking.

> Guido van Rossum wrote:
> > I don't see imageop in the list of deprecated modules in PEP 4, and
> > apparently *you* are still using it, so as long as you don't mind
> > being potentially the sole maintainer and user, I don't mind these
> > being in the distribution.
> > 
> > What do you mean by different results on Linux?  Was this module
> > previously doing something bogus there?

[Sjoerd]
> The main difference is:
> ***************
> *** 570,577 ****
>    		r = (r<<5) | (r<<3) | (r>>1);
>    		g = (g<<5) | (g<<3) | (g>>1);
>    		b = (b<<6) | (b<<4) | (b<<2) | b;
> ! 		nvalue = r | (g<<8) | (b<<16);
> ! 		*ncp++ = nvalue;
>    	}
>    	return rv;
>    }
> --- 560,569 ----
>    		r = (r<<5) | (r<<3) | (r>>1);
>    		g = (g<<5) | (g<<3) | (g>>1);
>    		b = (b<<6) | (b<<4) | (b<<2) | b;
> ! 		*ncp++ = 0;
> ! 		*ncp++ = b;
> ! 		*ncp++ = g;
> ! 		*ncp++ = r;
>    	}
>    	return rv;
>    }
> 
> where the old ncp is an "Py_UInt32 *" and the new ncp is an "unsigned 
> char *".  This results in different byte ordering on a little endian 
> machine such as Intel.

Hm.  Anybody who uses the imageop module currently on Linux will find
their programs broken.  The strings manipulated by imageop all end up
either being written to a file or handed to some drawing code, and
changing the byte order would definitely break things!

So I don't think this is an acceptable change.  I take it that for
IRIX, the byte order implied by the old code is simply wrong?  Maybe
the module can be given a global (shrudder?) byte order setting that
you can change but that defaults to the old setting?

--Guido van Rossum (home page: http://www.python.org/~guido/)

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[Python-Dev] Fixes for imageop module