Crop pdf using qpdf and jq (2)

pdf_crop_qpdf2.sh

#!/usr/bin/env bash

if (( $# != 3 )); then
    echo Usage: $0 in.pdf out.pdf '"x_bl,y_bl,x_tr,y_tr"'
    exit 1
fi

##################################################
## jq code to get minimal(?) json for qpdf to use
## to patch the cropboxes for every page object

# save the page objects
cmd='[(.pages[].object | "obj:" + .)] as $pageObjects | '
# .qpdf needs to be an array with two entries.
# Copy the first entry .qpdf[0]
cmd+='{ qpdf: [ .qpdf[0], '
# For the second entry, select the page objects
# from .qpdf[1] and insert the cropboxes
cmd+='(.qpdf[1] | with_entries(select( .key as $k | any( $pageObjects[] == $k ))'
cmd+='				    | .value.value["/CropBox"] = ['"$3"'] )) ]}'
##################################################

tmp="$(tempfile)"
qpdf --json-output --json-key=pages "$1" | jq  "$cmd" > "$tmp"
qpdf "$1" --update-from-json="$tmp" "$2" && rm "$tmp"