Converting embedded images in PowerPoint to JPG

One user wanted to know how to convert a bunch of PNG images already embedded in a PowerPoint presentation to JPG so that lossy compression could be used to reduce the file size of the overall presentation. I'm not aware of a way to do that in VBA, but I know that PPTX files (like all modern Office documents) are actually ZIP archives, so I took advantage of that fact to write a script that opens a PPTX, converts all PNG files in /ppt/media to JPG, and puts them back into the archive. Interestingly, PowerPoint doesn't seem to care that the extension doesn't match the image format, so that made the job easier. I also included an optional -Quality parameter that specifies how good the resulting images need to look. The full script can be seen in my answer.