I OCR all the PDFs that the library sends me or that I scan myself so that (1) I can index and search them but also and especially (2) so that I can highlight them in my PDF reader and then extract those highlights into Zotero.
Sometimes, though, I get a rubbish scan that has too much colour and not enough contrast or brightness. The solution is Imagemagick. Here’s the incantation I found to help out my latest troublesome PDF:
convert -colorspace gray -density 300 -brightness-contrast 5x25 -sharpen 0x1 input.pdf output.pdf
So I’m:
- Making it grayscale:
-colorspace gray - Setting the pixel density:
-density 300 - Altering brightness and contrast:
-brightness-contrast 5x25 - Sharpening:
-sharpen 0x1
I tried -adaptive-sharpen 0x1 (which I thought would be better given its efficacy on edges and I’m mostly trying to remove shadows) but it seems to reduce the image resolution and I wasn’t getting better results. I’ll need to experiment with these settings but this worked well enough for my purposes.