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https://github.com/nicolashahn/diffimg
Differentiate images in python - get a ratio or percentage difference, and generate a diff image
https://github.com/nicolashahn/diffimg
diffing image-processing python testing-tools
Last synced: about 2 months ago
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Differentiate images in python - get a ratio or percentage difference, and generate a diff image
- Host: GitHub
- URL: https://github.com/nicolashahn/diffimg
- Owner: nicolashahn
- License: mit
- Created: 2016-03-30T15:54:15.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2023-05-18T11:30:36.000Z (over 1 year ago)
- Last Synced: 2024-10-29T05:17:16.724Z (2 months ago)
- Topics: diffing, image-processing, python, testing-tools
- Language: Python
- Homepage:
- Size: 3.19 MB
- Stars: 213
- Watchers: 12
- Forks: 26
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# diffimg
Get the % difference in images using PIL's histogram + generate a diff image. Images
should have the same color channels (for example, RGB vs RGBA). If the image dimensions
differ, the 2nd image will be resized to match the first before calculating the diff.
[](https://badge.fury.io/py/diffimg)
### Installation
Now available from PyPi: `pip install diffimg`
### Usage
```
>>> from diffimg import diff
>>> diff('mario-circle-cs.png', 'mario-circle-node.png')
0.007319618135968298
```
The [very simple](/diffimg/diff.py#L12) `diff` function returns a raw ratio instead of a
% by default.
```
diff(im1_file,
im2_file,
delete_diff_file=False,
diff_img_file=DIFF_IMG_FILE
ignore_alpha=False)
```
`im1_file, im2_file`: filenames of images to diff.
`delete_diff_file`: a file showing the differing areas of the two images is generated in
order to measure the diff ratio with the same dimensions as the first image. Setting
this to `True` removes it after calculating the ratio.
`diff_img_file`: filename for the diff image file. Defaults to `diff_img.png`
(regardless of inputed file's types).
`ignore_alpha`: ignore the alpha channel for the ratio and if applicable, sets the alpha
of the diff image to fully opaque.
### As command line tool
`python -m diffimg image1 image2 [-r/--ratio] [-d/--delete] [-f/--filename DIFF_IMG_FILE]`
`--ratio` outputs a number between 0 and 1 instead of the default `Images differ by X%`.
`--delete` removes the diff file after retrieving ratio/percentage.
`--filename` specifies a filename to save the diff image under. Must use a valid extension.
`--ignore-alpha` ignore the alpha channel.
### Tests
```
$ ./test.py
......
----------------------------------------------------------------------
Ran 6 tests in 0.320s
OK
```
### Formula
The difference is defined by the average % difference between each of the channels
(R,G,B,A?) at each pair of pixels Axy, Bxy at the same coordinates
in each of the two images (why they need to be the same size), averaged over all pairs
of pixels.
For example, compare two 1x1 images _A_ and _B_ (a trivial example, >1 pixels would have
another step to find the average of all pixels):
_A_1,1 = RGB(255,0,0) _(pure red)_
_B_1,1 = RGB(100,0,0) _(dark red)_
((255-100)/255 + (0/0)/255 + (0/0)/255))/3 = (155/255)/3 = 0.202614379
So these two 1x1 images differ by __20.2614379%__ according to this formula.
## Sample image 1
## Sample image 2
## Resulting diff image
## Difference percentage output
`Images differ by 0.731961813597%`