In order to have smaller images I always get the images of wikidata entries with ?width=800. This works fine in general but I had a problem with the image of Perrier.
URL I used for the image: https://commons.wikimedia.org/wiki/Special:FilePath/HK%20Peak%20Tower%20%E5%B1%B1%E9%A0%82%E5%87%8C%E9%9C%84%E9%96%A3%20food%20shop%20Perrier%20Drinking%20water.JPG?width=800
When calling the url not image/jpeg is returned as it should. Instead application/x-www-form-urlencoded is returned.
When trying other widths (I tried 300 and 1200) this works perfectly fine.
Also worth noting: When trying to get width 300 two times the size is the same (as it should). With width 800 it is far from being the same size.