Many "useful articles" referencing specifically numbered JPGs like are found in botanical and medical research papers. For example:

: You can find a deep dive into how JPGs are structured, including block splitting and entropy coding, at Compress-Or-Die . JPEG - an overview | ScienceDirect Topics

: JPG is a "lossy" format, meaning it discards data to reduce file size. A practical guide on Media Editing at University of York notes that 120 pixels per centimeter is a standard for high-quality printing.

If you are looking for general information on JPG files, these resources explain how they work and how to manage them:

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