[Image-SIG] pil rotate 90 bug ?

Guilherme Polo ggpolo at gmail.com
Thu Aug 4 22:24:51 CEST 2011

2011/7/28 Jeremy Craven <c.j.craven at sheffield.ac.uk>:
> I have a program that has been working fine rotating images by arbitrary
> angles.
> I just found that if I specify 90 degrees exactly then the image goes crazy:
> only appears in left hand half of image and every other line is black and
> image is stretched vertically.
> Any ideas if this is a bug or I am perhaps doing something in a
> non-recommended way.

It is a bug, it doesn't rotate the image by 90 degrees.

Looking through PIL code, I would think the problem is that you have
these "special images" with mode as "I;16B", which PIL marks as
IMAGING_TYPE_SPECIAL. The code paths used for such special things
probably are under tested.

> I attach a cut down version of the code which shows the problem. It reads
> "test_in.tif". It rotates it 90.0 and writes "test.tif". It rotates it 89.99
> and writes "test1.tif". The second output file looks fine. The first is
> wonky.
> I'm using version 1.1.7
> Thanks for listening
> Jeremy
> --
> *********************************************************************************
> Dr C. Jeremy Craven
> Department of Molecular Biology and Biotechnology
> University of Sheffield,
> Firth Court, Western Bank
> S10 2TN Sheffield UK

-- Guilherme H. Polo Goncalves

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