Take a look at the git log to see if you can at least explain one or two reasons why the original author added such non-sense. Was it a feature tackled on at a later date? Did they try to fix some bugs?
If you can't find a reason (or is not willing to do so), it's practically calling the previous programmer either a bad one, or just doesn't care about anything at all. In that case, refactoring might be the least of your concerns.
Checking the vcs history of the file to understand when, and perhaps why, the giant inlined png was added would be a good first step. Usually that will link you to bugs and work items in your issue tracker as well. At the very least you'll get the names of the people responsible, and if all else fails you can go ask them.
Stick around long enough in one place, and you'll end up doing git blame on some gnarly code and discover that the culprit responsible was... yourself.
If you can't find a reason (or is not willing to do so), it's practically calling the previous programmer either a bad one, or just doesn't care about anything at all. In that case, refactoring might be the least of your concerns.