measure-time-diff-for-separate-or-single.sh

#!/bin/bash
set -euo pipefail

main() {
    input=~/Downloads/testfifle.pdf
    outdir="./thumb"
    prefix="thumb"

    rm -rf $outdir && mkdir -p $outdir

    echo "---- single task"
    single_runner $input $outdir $prefix

    rm -rf $outdir && mkdir -p $outdir

    echo "---- separated task"
    separate_runner $input $outdir $prefix
}


separate_runner() {
  local input=$1
  local outdir=$2
  local prefix=$3

  rm -rf ./tmp && mkdir -p ./tmp

  pagenum=$(pdfinfo $input |grep Pages | cut -f2 -d ':' | tr -d " \n")

  echo "- separate to $pagenum pages"
  time pdfseparate $input ./tmp/$prefix-%d.pdf

  echo "- convert"
  time seq 1 $pagenum | xargs -L 1 -P $pagenum -I {} pdftocairo -png -transp -r 150 -singlefile ./tmp/$prefix-{}.pdf $outdir/$prefix-{}
}

single_runner() {
  local input=$1
  local outdir=$2
  local prefix=$3

  time pdftocairo -png -transp -r 150 $input $outdir/$prefix
}

# call main.
main "$@"

---- single task

real	3m55.679s
user	3m52.611s
sys	0m2.387s
---- separated task
- separate to 145 pages

real	0m14.721s
user	0m13.487s
sys	0m1.191s
- convert

real	0m59.012s
user	7m15.378s
sys	0m29.138s

macは6coreなので早くて当たり前ではある。。。