On 09-09-28, at 07:22, Fredrik Lundh wrote:
On Tue, Sep 1, 2009 at 4:44 AM, Etienne Desautels
<t...@sympatico.ca> wrote:
So after experimenting, I see 3 problems:
1. Resize with ANTIALIAS from a large JPEG to a small thumbnail
give poor
image quality.
This should work fine in 1.1.6; no time to look at your tests right
now, but I'll do that asap.
Since I wrote this, I resize (downsample) a lot more images with PIL
and in general the result is excellent. The problem appear only with
the kind of images I choose to do my initial tests, image of
concentric circles or alike. Now I'm pretty sure that the poor result
I saw is a special edge case of the antialias algorithm used in PIL. I
can't see any other explanation.
2. BICUBIC, when set, is not applied. Instead NEAREST is use.
The problem you're seeing is that PIL's BICUBIC filter has a fixed
size, and thus doesn't work well for large downsamplings (there's a
discussion about this in the documentation, iirc). The ANTIALIAS
filter does not have that shortcoming.
Ho, yes I see.
3. Converting from TIFF CMYK to RGB shift the colors dramatically.
This is a bug in 1.1.6 and earlier (well, strictly speaking, it's a
old bug in Photoshop, but I guess we're not really in a position to
make them change their implementation ;-). It's fixed in 1.1.7.
There's also a drop-in replacement JPEG plugin by Kevin Cazabon that
fixes this for earlier versions (in a somewhat roundabout way, due to
a bug in the core library that has also been fixed in 1.1.7); see:
http://mail.python.org/pipermail/image-sig/2006-April/003871.html
I saw some threads about this bug but I was with the impression that
applied only to the JPEG plugin, not to the CMYK support in general ?
Etienne
</F>
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