Added an `image.entropy()` method (second revision) by fish2000 · Pull Request #3608 · python-pillow/Pillow

fish2000 · 2019-01-25T17:48:12Z

This calculates the entropy for the image, based on the histogram.

Because this uses image histogram data directly, the existing C function underpinning the image.histogram() method was abstracted into a static function to parse extrema tuple arguments, and a new C function was added to calculate image entropy, making use of the new static extrema function.

The extrema-parsing function was written by @homm, based on the macro abstraction I wrote, during the discussion of my first entropy-method pull request: #3530 (comment)

The original PR had code with issues with log2 and the use of the standard math library – @radarhere corrected these: fish2000#1

The new image.entropy() method is based on image.histogram(), and will accept the same arguments to calculate the histogram data it will use to assess the entropy of the image.

The algorithm and methodology is based on existing Python code:

https://github.com/fish2000/instakit/blob/44893861972b16e279ad0fe3f9dc1f84b39004b4/instakit/processors/squarecrop.py#L11-L25

... A test case in the Tests/ directory, and doctest lines in selftest.py, have both been added and checked.

Changes proposed in this pull request:

Adding the <math.h> include to _imaging.c,
The addition of an image.entropy() method to the Image Python class,
The abstraction of the extrema-parsing logic of of the C function _histogram into a static function, and
The use of that static function in both the _histogram and _entropy C functions.
Minor documentation addenda in the docstrings for both the image.entropy() and image.histogram() methods were also added.

This resolves my earlier version of this feature, PR #3530.

fish2000 · 2019-02-01T17:46:55Z

@homm @radarhere Might I get a review on this, if either of you get a moment?

src/_imaging.c

Tests/test_image_entropy.py

src/_imaging.c

fish2000 · 2019-02-06T21:07:31Z

… OK so it looks like /usr/bin/xvfb-run segfaulted in one of the QImage tests during the Docker Arch run – but otherwise everything else on the latest Travis build-flight passed it would seem, erm yes.

fish2000 · 2019-03-04T19:22:13Z

Any chance of getting this into version 6.0.0? – q.v. issue #3618 supra.

Tests/test_image_entropy.py

src/_imaging.c

@homm

This calculates the entropy for the image, based on the histogram. Because this uses image histogram data directly, the existing C function underpinning the `image.histogram()` method was abstracted into a static function to parse extrema tuple arguments, and a new C function was added to calculate image entropy, making use of the new static extrema function. The extrema-parsing function was written by @homm, based on the macro abstraction I wrote, during the discussion of my first entropy-method pull request: https://git.io/fhodS The new `image.entropy()` method is based on `image.histogram()`, and will accept the same arguments to calculate the histogram data it will use to assess the entropy of the image. The algorithm and methodology is based on existing Python code: * https://git.io/fhmIU ... A test case in the `Tests/` directory, and doctest lines in `selftest.py`, have both been added and checked. Changes proposed in this pull request: * Added “math.h” include to _imaging.c * The addition of an `image.entropy()` method to the `Image` Python class, * The abstraction of the extrema-parsing logic of of the C function `_histogram` into a static function, and * The use of that static function in both the `_histogram` and `_entropy` C functions. * Minor documentation addenda in the docstrings for both the `image.entropy()` and `image.histogram()` methods were also added. * Removed outdated boilerplate from testing code * Removed unused “unittest” import

hugovk · 2019-06-29T07:13:32Z

Thank you! This will be released on Monday.

Please could you add release notes to https://github.com/python-pillow/Pillow/blob/master/docs/releasenotes/6.1.0.rst#api-additions?

hugovk · 2019-07-01T06:12:39Z

Release notes added in #3930.

Add release notes for #3608, #3861 and #3886

fish2000 mentioned this pull request Jan 25, 2019

Added image.entropy() method #3530

Closed