There's lots of great free open source software out there, but sometimes it can be challenging to find a simple utility to accomplish a task. I was trying to extract some images from a PDF file for further processing and could not find an easy solution. Therefore, I've created this tool called PDFImgEx for extracting all images from a PDF in their native format. It only does this one task, no conversion or post-processing.
It is a command line tool written in C#. Currently, it is only available for Windows. However, the source is available on GitHub if anyone wishes to port it to .NET Core or some other language. It is really just a wrapper around iTextSharp.
A compiled release for Windows is available here. Extract the zip and view the readme.txt file to get acquainted.
It can be used in conjunction with ImageMagick when conversion is necessary. If you are dealing with JP2 (JPEG 2000) files, I recommend ImageMagick. Here's a great little command to convert .JP2 files into PNGs:
magick mogrify -format png *.jp2
Please let us know if you find it useful.