Test fails with cryptic error message if fresh image is larger then baseline image (imagemagick) #75

Expected Output

assertSameFiles Needle should either state that the images are similar or that they are not.

Actual Output

ValueError: ("could not convert string to float: b'idt'") thrown at /needle/engines/imagemagick_engine.py:24

• Checking the compare_stderr in that situation yields compare: width or height exceeds limit [...]
• Running the actual command stored incompare_cmd in a console yields the same error
• However I don't think this this an imagemagick bug since the intention -subimage-search is to find a smaller image inside a bigger one.

Reproduce

1. create an images 1.png and 2.png where 2.png is bigger then 1.png
2. run magick compare -metric RMSE -dissimilarity-threshold 1.0 -subimage-search 1.png 2.png d.png
3. get compare: width or height exceeds limit '1.png' @ error/cache.c/OpenPixelCache/3491.

Suggestions

We could order the images by size. However I guess that will not fix the problem is one image is wider but not as high as the other one.

Contribution

I tried to run the tests but many fail on my system. I'm not sure if that is a problem with the tests or with me not using the right commands. I created an issue #74
If this issue is solved I'd be happy to implement my the reordering of the images.