PDF Tidbits

Invert PDF Colors

(Useful for PDF "darkmode".)

Start a Docker container with a bind volume mount to the current directory:
```
docker run --rm -it -v "$PWD:/mnt" alpine
```
Install Ghostscript within the container:
```
apk add --no-cache ghostscript
```

Invert colors on the desired PDF:

gs -o /mnt/input.pdf \
   -sDEVICE=pdfwrite \
   -c '{1 exch sub}{1 exch sub}{1 exch sub}{1 exch sub} setcolortransfer' \
   -f /mnt/output.pdf

NOTE: Not all PDF viewers will respect this method of inverting PDF colors. See reference below for more information.