Cool site, nice one. There's potential to save a lot of time when going back and forth between cropping tools. One of my usual workflows is reading big PDFs and I want to pick out the parts that are relevant to me. I could use a highlighter, but that wouldn't filter out the rest of the document, so I typically use a screenshot tool to grab specific areas and save them as pictures. But it can only make one screenshot at a time, which is a lot of overhead.

It would be cool to enhance this site so that it takes a PDF with multiple pages and allow you to do the same for that. But that's probably a lot of work compared to uploading a single picture file!