Image Compare By Pixels

How to compare 2 images to check if it is identical. The easiest way is to compare pixel by pixel of the 2 images.

In my example, I am using Python Pillow to compare. To install it in macOS, just run these 2 lines

python3 -m pip install --upgrade pip
python3 -m pip install --upgrade Pillow

For other OS, you can refer to their official site at https://pillow.readthedocs.io/en/stable/installation.html

The source code of my function

WebP to PNG conversion. No pixel edited.

PNG with 1 pixel edited (1 black dot right above the head).

WebP

1. I downloaded a 360x360 WebP image from Google PlayStore and named it a.webp
2. Duplicate a.webp to b.webp
3. Edit 1 pixel in b.webp in GIMP

2% similarity with 1 pixel change

PNG

1. Converted a.webp to a.png using ImageMagick
2. Duplicate a.png to b.png
3. Edit 1 pixel in b.png

convert a.webp a.png

99% similarity with 1 pixel change

BMP

1. Converted a.webp to a.bmp using ImageMagick
2. Duplicate a.bmp to b.bmp
3. Edit 1 pixel in b.bmp

convert a.webp a.bmp

99% similarity with 1 pixel change

GIF

1. Converted a.webp to a.gif using ImageMagick
2. Duplicate a.gif to b.gif
3. Edit 1 pixel in b.gif

convert a.webp a.gif

99% similarity with 1 pixel change

JPG

1. Converted a.webp to a.jpg using ImageMagick
2. Duplicate a.jpg to b.jpg
3. Edit 1 pixel in b.jpg
4. Save as 100% quality

convert a.webp a.jpg

87% similarity with 1 pixel change

Conclusion

My favorite file type is PNG although GIF has a smaller file size because GIF looks grainy after the conversion with default settings.

Works with
- GIF, PNG, BMP

Does NOT work with
- WebP, JPG

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