Apple's JPG compression is a mess
For PDFify I wrote a custom squeeze algorithm for PDF files to fit the need of my customers. One optimization is to compress the contained image files. I used the usual on board tools of macOS to create JPG files with a certain compression. This is where the mess started...
Poor documentation, wrong assumptions
I was under the impression, that compression would refer to JPG quality expressed in percent. That assumption was wrong, instead the