I've noticed that many contributed PDFs in the IMSLP library have not been contrast-adjusted to remove dark backgrounds. This makes them harder to read, and greatly increases their file sizes (including all the extra background data).
In the past, I've "cleaned up" such PDFs by extracting each page as an image file; editing them in an image editor; then saving the images as PDF files and merging them back into one document. Image editors like IrfanView (for Windows) have batch-processing options for processing multiple files, so that helped, but it was still laborious.
Tonight I discovered this older, but still functional, freeware PDF viewer for Windows:
STDU Viewer
https://www.softpedia.com/get/Office-to ... ewer.shtml
It's no longer developed, so the link I've included above is to its page at Softpedia.com, a long-established, reputable software site.
With STDU Viewer, you can open a PDF file, then use its Settings options (on the View menu) to change brightness, contrast, and gamma values as you watch. You can then "print" the changed document as a new PDF (File > Print, using whatever PDF-creation software you've also installed).
With STDU and the free PDFCreator (using its "High Compression" profile), I just removed the gray backgrounds from a 71-page PDF of Bach keyboard suites, reducing it from 94 MB to 35 MB with no loss of quality.
I don't think I should attach the scores here, due to their sizes. However, I've posted this screenshot of the "before" and "after" versions of the title pages on Postimage.org, an image-sharing site, so you can see the difference in quality. This was with a single brightness/contrast/gamma setting I applied to the whole document.
I'd like to upload the improved version of the score to IMSLP—but unfortunately I can't read Russian, so I can't find the score's page again!
If anyone recognizes the score, will you please post its address here so I can upload it to the proper place?I hope someone finds this helpful! Cheers, Andy