Hi Lars, On Mon, Oct 29, 2012 at 4:05 PM, Lars Ruoff <lars.ru...@gmail.com> wrote:
> Any other comments? > > Alex, > > Pillow says: > Please report any non-packaging related issues here first: > > - https://bitbucket.org/effbot/pil-2009-raclette/issues > > > Should i report the issue there? > Yes please. > > Lars > > > > On Mon, Oct 29, 2012 at 4:33 PM, Alex Clark <acl...@aclark.net> wrote: > >> On 2012-10-29 15:05:28 +0000, Lars Ruoff said: >> >> Hi, >>> >>> I'm new to this list, so excuse me if this is a known issue. >>> I didn't find anything on it on the net so far but didn't have time to >>> search much. >>> >>> I have observed what i consider a flaw in the Image.paste algorithm when >>> used with transparent images. >>> >>> transparent-columns.png is an image with 3 vertical black columns with >>> alpha=0.5, 0.2 and transparent respectively. >>> transparent-bars.png is an image with 2 horizontal black bars with >>> transparent and alpha=0.5 respectively. >>> (images attached) >>> >>> When these two images are transparently pasted one over the other, using >>> the following code: >>> >>> from PIL import Image >>> source = Image.open('transparent-**columns.png') >>> result = Image.open('transparent-bars.**png') >>> result.paste(source, (0, 0), source) >>> result.save('transparent-**columns-on-bars-pil.png') >>> >>> The result is unexpectet to say the least. >>> PIL seems to modify the transparency even in regions where only one of >>> the images has non-transparent values. >>> Very wrong in my opinion. >>> >>> Doing the same manipulation in GIMP 2.6 gives what i consider the >>> expected result. >>> (attached for reference) >>> >>> I guess the per-pixel transparency of the result should be result_alpha >>> = 1 - (1-alpha1)*(1-alpha2), >>> where alpha1,alpha2 are the alpha channel values from the original >>> images. >>> >> >> >> You are welcome to submit a patch to Pillow (the "friendly" PIL fork) >> here: >> >> - >> https://github.com/python-**imaging/Pillow<https://github.com/python-imaging/Pillow> >> >> >> Speaking of that, can anyone review: >> >> - >> https://github.com/python-**imaging/Pillow<https://github.com/python-imaging/Pillow> >> >> >> Also, I'm looking for a few folks willing to "stand up" and regularly >> review image code fixes. I know nothing about that code, and plan to stick >> with being the release manager only. I'll be doing a 1.7.8 release soon (by >> the end of this month) then maybe Pillow 1.8 will contain support for >> Python 3.3 (and cut everything before 2.7). >> >> >> >>> Regards, >>> Lars Ruoff >>> >>> <image> >>> <image> >>> <image> >>> <image> >>> <image> >>> <image> >>> ______________________________**_________________ >>> Image-SIG maillist - Image-SIG@python.org >>> http://mail.python.org/**mailman/listinfo/image-sig<http://mail.python.org/mailman/listinfo/image-sig> >>> >> >> >> -- >> Alex Clark · >> https://www.gittip.com/**aclark4life/<https://www.gittip.com/aclark4life/> >> >> >> ______________________________**_________________ >> Image-SIG maillist - Image-SIG@python.org >> http://mail.python.org/**mailman/listinfo/image-sig<http://mail.python.org/mailman/listinfo/image-sig> >> > > -- Alex Clark · http://aclark.net
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