Convert PDF into PNG files
sudo apt update
sudo apt install poppler-utils
Usage
pdftoppm -png input.pdf output_name

Technical notes, and other ideas.
Convert PDF into PNG files
sudo apt update
sudo apt install poppler-utils
Usage
pdftoppm -png input.pdf output_name
Refer: https://superuser.com/questions/577643/how-do-i-batch-convert-thousands-of-nefs-to-jpegs
Install Applications
sudo apt-get install netpbm dcraw
Convert One Image
dcraw -c -w input.NEF | pnmtopng > output.png
Run Application Against Multiple Files
for filename in *.NEF ; do dcraw -c -w "$filename" | pnmtopng > "$filename.png" ; done
Problem viewing a PNG, could be the new WebP format from Google.
On Ubuntu you can use gThumb or XnView
Review: https://itsfoss.com/webp-ubuntu-linux/
Installing ImageMagic
$ sudo apt-get install imagemagick imagemagick-doc
The new Yellow Colors are this:
Selected state: #FFCB66
Hover state: #FCB614
The interesting thing about ImageMagic is the convert actually has the target color first and the color to replace second, as a parameter.
In order to change the colors for the location_and_decks, do the following:
Use the PNG files because they are lossless and convert them.
This is for changing blue to yellow for the selected items
for f in *.png; do
convert ./"$f" -fuzz 0% -fill "#FFCB66" -opaque "#0D932C" ../../locations_and_decks/"$f"
done
Unfortunately, the hovers for blue, were the same color as the border, so we took the selected and converted them to hovers; however, the names needed to be changed too.
for f in *.png; do
convert ./"$f" -fuzz 0% -fill "#FCB614" -opaque "#0D932C" ../../locations_and_decks/hover/"$f"
done
After getting all of the PNG's into the same folder you can use the following to convert all of the PNG files into JPG files.
for f in *.png; do
convert ./"$f" -background white -flatten -alpha off ../locations_and_decks/"${f%.png}.jpg"
done