`astropy.io.fits.diff:ImageDataDiff`

source: /astropy/io/fits/diff.py :979

Signature

   class     ImageDataDiff (    a    ,    b    ,    numdiffs    =  10   ,    rtol    =  0.0   ,    atol    =  0.0     )

Diff two image data arrays (really any array from a PRIMARY HDU or an IMAGE extension HDU, though the data unit is assumed to be "pixels").

ImageDataDiff objects have the following diff attributes:

diff_dimensions: If the two arrays contain either a different number of dimensions or different sizes in any dimension, this contains a 2-tuple of the shapes of each array. Currently no further comparison is performed on images that don't have the exact same dimensions.
diff_pixels: If the two images contain any different pixels, this contains a list of 2-tuples of the array index where the difference was found, and another 2-tuple containing the different values. For example, if the pixel at (0, 0) contains different values this would look like
```
[(0, 0), (1.1, 2.2)]
```
where 1.1 and 2.2 are the values of that pixel in each array. This array only contains up to self.numdiffs differences, for storage efficiency.
diff_total: The total number of different pixels found between the arrays. Although diff_pixels does not necessarily contain all the different pixel values, this can be used to get a count of the total number of differences found.
diff_ratio: Contains the ratio of diff_total to the total number of pixels in the arrays.