download as pdf from Dropbox when the download option is disabled

download-disabled-dropbox.sh

#!/bin/bash -eu
# first, get the image URLs using such as Chrome DevTools
# The URLs is assumed to be "xxxxx?page={page number}"
URI=("https://path/to/file1" "https://path/to/file2")
PAGES=(10 20)

RED=""
GREEN=""
BLUE=""
NORMAL=""
if which tput >/dev/null 2>&1; then
  ncolors=$(tput colors)
  if [ -t 1 ] && [ -n "$ncolors" ] && [ "$ncolors" -ge 8 ]; then
    RED="$(tput setaf 1)"
    GREEN="$(tput setaf 2)"
    BLUE="$(tput setaf 4)"
    NORMAL="$(tput sgr0)"
  fi
fi

# check
if ! type wget  > /dev/null 2>&1 ; then
  echo "please install wget."
  exit 1
fi

if ! type convert > /dev/null 2>&1 ; then
  echo "please install imagemagick."
  exit 1
fi

# main
# -----------
for ch in `seq 0 $(( ${#URI[@]}-1 ))` ; do
  echo "chapter $(( $ch+1 )):"
  # download
  for i in `seq 0 ${PAGES[$ch]}` ; do
    echo "==> wget ${URI[$ch]}$i -O $i.png"
    wget ${URI[$ch]}$i -O $i.png > /dev/null 2>&1
  done

  # convert
  echo "${BLUE}==> convert {0..${PAGES[$ch]}}.png ch$(( $ch+1 )).pdf$NORMAL"
  eval convert {0..${PAGES[$ch]}}.png ch$(( $ch+1 )).pdf
  if [ $? = 0 ]; then
    echo "${BLUE}==> rm {0..${PAGES[$ch]}}.png$NORMAL"
    eval rm {0..${PAGES[$ch]}}.png
    echo "${GREEN}saved chapter $ch files to ch$(( $ch+1 )).pdf. ✔︎ $NORMAL"
  else
    echo "${RED}An unexpected error occurred when converting png files to pdf.$NORMAL"
    exit 1
  fi
done