how-tos

• extract images from a PDF pdfimages -png file.pdf imagefile
• increase contrast in a bunch of images for f in *.png; do echo $f; convert $f -level 25%,100% $f.contraste.png; done
• add images to a new PDF
  img2pdf $(find . -iname '*.png' | sort -V) -o ./document.pdf
• compress a PDF
  gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/prepress -dNOPAUSE -dQUIET -dBATCH -sOutputFile=compressed_document.pdf document.pdf
• transcode video
  ffmpeg -i /path/to/original/videofile.format /path/to/new/file.format
• download from academia.edu
  https://github.com/dvtng/jss