I've attached a patched JpegImagePlugin.py file (sorry for the 14.5kb 
attachment to a mailing list).  It should fix the inversion problem both 
upon load and upon save of CMYK JPEG files.

Modifications can be found starting on the following lines:

line 35:  add ImageChops to the import list, for inverting images

line 273:  comment out previous patch for Adobe Photoshop 2.5 CMYK files... 
I sure hope nobody uses 2.5 anymore, and this patch breaks newer versions.

line 288:  invert CMYK images after load

line 416:  invert CMYK images before save


I'm sure there are more elegant an efficient ways of fixing this problem, 
but this works.  I hope it helps you, as I've had the same issues myself.

Fredrik - if you're ok with the crude methods of fixing this problem, can 
you include it in future builds?  Thanks.

Kevin.


----- Original Message ----- 
From: <kevin@[...].com> 
To: <kevin@[...].com> ; "Cesare Leonardi" <ced@[...].com>; 
<image-sig@[...].org> 
Sent: Saturday, April 15, 2006 2:01 PM
Subject: Re: [Image-SIG] Problem with JPEG and CMYK color space


>  In the JPEGImagePlugin.py module, there's a hack to handle Photoshop 2.5 
>  CMYK JPEG images (around line 273)... that's causing half the problem upon 
>  loading JPEG's.  By commenting that out, you get a proper image, although 
>  it's still inverted.
> 
>  I can't seem to find the right place to re-invert the image upon load, but 
>  I'll see what I can find.  Anyone with suggestions would be welcome. 
>  There's probably a better way to do this though, so the data is read 
>  correctly in the first place (in CMYK, 0,0,0,0 = white, 255,255,255,255 = 
>  full black... this is probably the problem).
> 
>  Kevin.
>  ----- Original Message ----- 
>  From: <kevin@[...].com>
>  To: "Cesare Leonardi" <ced@[...].com>; <image-sig@[...].org>
>  Sent: Saturday, April 15, 2006 1:32 PM
>  Subject: Re: [Image-SIG] Problem with JPEG and CMYK color space
> 
> 
> > Actually, the problem is that PIL also has problems reading CMYK JPEG 
> > files
> > apparently.  I just proved that by loading your CMYK test files and doing 
> > a
> > "show", then loading a CMYK TIFF file and doing a show (note that to use
> > show, it converts to RGB with the internal conversion, so the colors 
> > won't
> > be perfect).  The TIFF loaded fine, the JPEG didn't.
> >
> > The patch I've submitted fixes the problem with saving incorrectly, but
> > doesn't fix the reading issue (yet).  So, as long as your source CMYK 
> > image
> > doesn't come from a JPEG file it's ok (with my invert patch).
> >
> > I'll see if I can spend some time looking at that this weekend.
> >
> > Kevin.
> > ----- Original Message ----- 
> > From: "Cesare Leonardi" <ced@[...].com>
> > To: <image-sig@[...].org>
> > Sent: Friday, April 14, 2006 9:38 AM
> > Subject: Re: [Image-SIG] Problem with JPEG and CMYK color space
> >
> >
> >> kevin@[...].com ha scritto:
> >>> When saving a CMYK file to JPG, PIL seems to invert the colors.  I've
> >>> submitted a patch to Fredrik already for this, and it should be in the
> >>> next major build.
> >>>
> >>> Adding a simple invert to the image before saving will help.
> >>
> >> Thanks all for your responses.
> >>
> >> Kevin, i've made some tests following what you've suggested and here is
> >> the results.
> >> To obtain the color inversion i've used the function invert() in
> >> ImageChops module. I've added the code and the new sample images in this
> >> page (see "part 2"):
> >> http://www.bernispa.com/pil/index.html
> >>
> >> As you can see your suggestion works partially.
> >> Images 02 and 03 (that was particular in "part 1") are the only that
> >> after the inversion looks ok.
> >> All the other images looks less dark, but the color are always different
> >> than the original.
> >> The particular thing to note is that the images produced by the
> >> inversion looks the same as Image.show(). Seems that show() already do
> >> the inversion.
> >>
> >> There is another thing that i have noted only now: the images saved by
> >> PIL are often less big than the original. Sometimes much less. For
> >> example:
> >> test01: 1435 KB   test01-dst: 198 KB   test01-dst-invert: 198 KB
> >> test04: 1237 KB   test01-dst: 405 KB   test01-dst-invert: 405 KB
> >> test08: 1647 KB   test01-dst: 777 KB   test01-dst-invert: 776 KB
> >> test09: 1715 KB   test01-dst: 665 KB   test01-dst-invert: 665 KB
> >> test10: 2032 KB   test01-dst: 659 KB   test01-dst-invert: 659 KB
> >> I can think that PIL optimize the compression, but that difference are
> >> really big. Isn't it suspicious? I expect that saving an image in a new
> >> file without modifications produces a file very similar to the original,
> >> isn't it?
> >> The original images was not produced by me so the author can have used
> >> low compression. I cannot make tests since i haven't a program that can
> >> save in CMYK (Gimp seems not able).
> >>
> >> Regards.
> >>
> >> Cesare.
> >> _______________________________________________
> >> Image-SIG maillist  -  Image-SIG@[...].org
> >> http://mail.python.org/mailman/listinfo/image-sig
> >>
> >>
> >>
> >
> >
> > _______________________________________________
> > Image-SIG maillist  -  Image-SIG@[...].org
> > http://mail.python.org/mailman/listinfo/image-sig
> >
> >
> >
> 
> 
> 
> 
>