How To Compare Two Imagefile From Two Different Files In Python

I would like to create a program that compares two images. I need to take images from two different folders and compare that images if they are same or not. Then I want to print ou

Solution 1:

Use ImageMagick, it is available for Python and included on most Linux distros. Get familiar at the commandline first, then work it up into Python.

Create two directories

mkdir directory{1..2}

Create a black square in directory1

convert-size 128x128 xc:black directory1/1.png

Create a black square with a red 10x10 rectangle in directory2

convert-size 128x128 xc:black -fill red -draw "rectangle 0,0, 9,9"  directory2/2.png

Now ask ImageMagick to tell us how many pixels are different between the two images, -metric ae is the Absolute Error.

convert directory1/1.png directory2/2.png -metric ae -compare -format"%[distortion]" info:

Output

100

Note 1

If you want to allow the images to be nearly the same, you can add -fuzz 10% which will allow each pixel to differ by up to 10% from the corresponding pixel in the other image before counting it as different. This may be more useful when comparing JPEG images which may have slightly different quality/quantisation settings, and/or anti-aliasing, both of which cause images to differ slightly.

Note 2

You can shell out from Python and run shell scripts like the above using this... link

Note 3

If you create, say a red GIF and a red PNG, and copare them, they will come up identical, like this

# Create red GIF
convert -size 128x128 xc:red red.gif
# Create red PNG
convert -size 128x128 xc:red red.png
# Compare and find no difference
convert red.png red.gif  -metric ae -compare -format"%[distortion]" info:
0

despite the fact that the files theselves differ enormously

ls -l red*
-rw-r--r--1mark  staff  1961 Apr 11:52 red.gif
-rw-r--r--  1 mark  staff  2901 Apr 11:52 red.png