Honestly there's such a gap between what the person thinks when they are doing when they create a no-derivatives license, and what they are actually doing, resizing probably doesn't matter. My official legal advice, as a person who has no legal qualifications whatsoever, is that these kind of mechanical transformations, with no real editorial intent (though there are still decisions like JPEG quality to make), are probably accepted by the license.
What would probably be more dangerous, and not allowed by the license, is embedding it in a wiki article to produce adapted material. You're producing an entirely different document in a wiki, using the no-derivative license as a subset. This is different from, say, showing it on a File: page, or on danbooru, where you're putting website material around it as a technical adaptation to display and index the content. The wiki article uses editorial choice, thus it is an adaptation. You can still use it by asserting a fair use exception to copyright -- in the United States, that is. Since the wiki is in the UK, you'd need to assert fair dealing instead -- most likely "copyright infringement for the purpose of non-commercial research". It could also be covered under "criticism or review", but only if the no-derivs work itself is the work under review.
The no-derivatives license is the equivalent of a museum that has a free admission price. You can come in all you want, but photography is forbidden, you can't rearrange the pictures, you can study it for your art class, but if you want to make a jigsaw puzzle of the art you need to buy it at the gift shop like everyone else.
What would probably be more dangerous, and not allowed by the license, is embedding it in a wiki article to produce adapted material. You're producing an entirely different document in a wiki, using the no-derivative license as a subset. This is different from, say, showing it on a File: page, or on danbooru, where you're putting website material around it as a technical adaptation to display and index the content. The wiki article uses editorial choice, thus it is an adaptation. You can still use it by asserting a fair use exception to copyright -- in the United States, that is. Since the wiki is in the UK, you'd need to assert fair dealing instead -- most likely "copyright infringement for the purpose of non-commercial research". It could also be covered under "criticism or review", but only if the no-derivs work itself is the work under review.
The no-derivatives license is the equivalent of a museum that has a free admission price. You can come in all you want, but photography is forbidden, you can't rearrange the pictures, you can study it for your art class, but if you want to make a jigsaw puzzle of the art you need to buy it at the gift shop like everyone else.
"Kitto daijoubu da yo." - Sakura Kinomoto