Extract PDF images in parallel

extract_pdf_images_in_parallel.sh

# For each page in input.pdf, 
# generate image(s) in PNG format
# named output_<PAGE>.png
# where PAGE is a 4-digit zero-padded number.
pdfinfo input.pdf \
  | grep Pages \
  | awk -F'[: ]*' '{print $2}' \
  | xargs seq \
  | parallel \
    '\
    p=$(printf "%04d\n" {}); \
    echo page ${p}; \
    pdfimages -png -f {} -l {} \
    input.pdf \
    output_${p}'