02-25-2021, 09:24 PM
Quote:I need to scan a massive load of textbooks, and am trying to figure out the best way to do it.
Best way? Probably not Gimp, but what type 'format' are the textbooks? Mostly text with a few diagrams? Mixtures of text and pictures ? Mostly colour pictures ?
Quote:I have made some test scans to JPEG, 300dpi, Colour. Which look kind of OK, pixilated obviously when zoomed in.
300 ppi is photo quality, anything will look pixelated to a certain degree under extreme magnification but consider viewing at normal reading size.
Quote:But I imported those same JPEGs to GIMP, and exported as a PDF, and it made them look a load better, smoother. The 4 JPEGS are 1.95 MB together But the PDF from GIMP is 13.2 MB
I gather this might have something to do with GIMP converting the JPEGs into Bitmap (is it?).
Gimp 'embeds' the scanned jpeg images in the PDF 'wrapper' but not with jpeg compression. It is compressed but not as much. A little bit about it here. https://gitlab.gnome.org/GNOME/gimp/-/issues/6117
Quote:I want the nice smooth PDF but without the much bigger file size. Is that possible?...
How to make smaller ? Stick with jpeg and for photo quality, 300 ppi but for pure text and line illustrations use a greyscale scan.
If the scans are not already made, try scanning directly into LibreOffice https://www.libreoffice.org/ (AFAIK the Windows TWAIN scan is back to working) LO has very good PDF exporting functions.
If the scans are already made then command line ImageMagick https://imagemagick.org will join a series of jpegs into a single PDF. Size not much more than the sum of the image sizes.
Code:
convert *.jpg -units pixelsperinch -density 300 file.pdfJust a note about opening pdf's in Gimp. The default ppi is 100 even when the pdf was made with 300 ppi. You can increase the ppi in the Open PDF dialogue.