python-pillow/Pillow
1
1
Fork 0
mirror of https://github.com/python-pillow/Pillow.git synced 2025-01-12 02:06:18 +03:00
Code Issues Packages Projects Releases Wiki Activity

chapters:

Browse Source 
Image resizing filters
Bicubic and Bilinear downscaling
Lanczos upscaling quality
Bicubic upscaling quality
This commit is contained in:
homm 2014-11-30 03:09:39 +03:00
parent 7382b789fc
commit b183f50ebc
1 changed files with 31 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
docs/releasenotes/2.7.rst
View File

@ -4,14 +4,36 @@ Pillow 2.7
Image resizing filters Image resizing filters
---------------------- ----------------------
Bicubic and Bilinear downscalling Image resizing methods :py:meth:`~PIL.Image.Image.resize` and
:py:meth:`~PIL.Image.Image.thumbnail` takes `resample` argument, which tells
what filter should be used for resampling. Possible values are:
:py:attr:`PIL.Image.NEAREST`, :py:attr:`PIL.Image.BILINEAR`,
:py:attr:`PIL.Image.BICUBIC` and :py:attr:`PIL.Image.ANTIALIAS`.
Almost all of them was changed in this version.
Bicubic and Bilinear downscaling
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
From very begining :py:attr:`~PIL.Image.BILINEAR` and
:py:attr:`~PIL.Image.BICUBIC` filters was based on afine transformations
and uses fixed number of pixels from source image for every destination pixel
(that was 2x2 pixels for :py:attr:`~PIL.Image.BILINEAR` and 4x4 for
:py:attr:`~PIL.Image.BICUBIC`). This gave an unsatisfied result for downscaling.
At the same time high quality convolutions-based algorithm with flexeible kernel
was used for :py:attr:`~PIL.Image.ANTIALIAS` filter).
Starting from 2.7 high quality convolutions-based algorithm is used for all of
these three filters.
If you have previously used any tricks to maintain quality when downscaling with
:py:attr:`~PIL.Image.BILINEAR` and :py:attr:`~PIL.Image.BICUBIC` filters
(for example, reducing within several steps), they a unnecessary now.
Antialias renamed to Lanczos Antialias renamed to Lanczos
^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
New :py:attr:`PIL.Image.LANCZOS` constant was added instead of New :py:attr:`PIL.Image.LANCZOS` constant was added instead of
:py:attr:`PIL.Image.ANTIALIAS`. :py:attr:`~PIL.Image.ANTIALIAS`.
When :py:attr:`~PIL.Image.ANTIALIAS` was initially added, it was the only When :py:attr:`~PIL.Image.ANTIALIAS` was initially added, it was the only
high-qality filter based on convolutions. It's name was supposed to reflect high-qality filter based on convolutions. It's name was supposed to reflect
@ -25,9 +47,16 @@ and is an alias for :py:attr:`~PIL.Image.LANCZOS`.
Lanczos upscaling quality Lanczos upscaling quality
^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^
Image upscaling quality with :py:attr:`PIL.Image.LANCZOS` filter was almost
the same as :py:attr:`PIL.Image.BILINEAR` due to bug. This was fixed.
Bicubic upscaling quality Bicubic upscaling quality
^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^
:py:attr:`~PIL.Image.BICUBIC` filter for affine trnsformations was producing
sharp, slightly pixelated image for upscaling. Bicubic for convolutions is
more soft.
Resize performance Resize performance
^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^