tinypdf-script-poc

#!/bin/bash

# Thanks to Mickaël
# src: https://superuser.com/a/1217306

# gs options:
# -dPDFSETTINGS=/screen   (screen-view-only quality, 72 dpi images)
# -dPDFSETTINGS=/ebook    (low quality, 150 dpi images)
# -dPDFSETTINGS=/printer  (high quality, 300 dpi images)
# -dPDFSETTINGS=/prepress (high quality, color preserving, 300 dpi imgs)
# -dPDFSETTINGS=/default  (almost identical to /screen)

pdftrim_usage() {
    printf "%s\n" 'Usage: pdftrim [input file] [output file] [screen|ebook|printer|prepress]'
    printf "\n%s\n\n" 'Example: pdftrim input.pdf output.pdf ebook'
    printf "%s\n" "Trim Options:"
    printf "%s\n" "  screen     - Screen-view-only quality, 72 dpi images"
    printf "%s\n" "  ebook      - Low quality, 150 dpi images"
    printf "%s\n" "  printer    - High quality, 300 dpi images"
    printf "%s\n" "  prepress   - High quality, color preserving, 300 dpi images"
    printf "%s\n" "  default    - Almost identical to /screen"
}

pdftrim() {
    if [ $# -lt 2 ]; then
        printf "%s\n" 'Error: Not enough arguments provided.'
        pdftrim_usage
        return 1
    fi
    if [ ! -f "$1" ]; then
        printf "%s\n" "Error: Input file '$1' does not exist."
        pdftrim_usage
        return 1
    fi
    if [ -z "$2" ]; then
        printf "%s\n" 'Error: Output file must be specified.'
        pdftrim_usage
        return 1
    fi

    # if not specified, use "screen" as default
    if [ -z "$3" ]; then
        printf "\n%s\n" 'Warning: No quality setting specified, using "screen" as default.'
    fi

    # gs -sDEVICE=pdfwrite -dNOPAUSE -dQUIET -dBATCH -dPDFSETTINGS=/${3:-"screen"} -dCompatibilityLevel=1.4 -sOutputFile="$2" "$1"

    #TODO: ask user for gray scale or color conversion based on that try filters

    # [EXPERIMENT] Use the following command to build a opinionated PDF based on the input file

    # pdfimages -list file.pdf | awk '$1 ~ /^[0-9]+$/ && $7 != 1 { found=1 } END { print (found ? "Color" : "Grayscale") }'
    # Download pdfimages @ https://poppler.freedesktop.org/

    # Docs: https://ghostscript.readthedocs.io/en/latest/VectorDevices.html#distiller-parameters

    gs -sDEVICE=pdfwrite \
        -dCompatibilityLevel=1.4 \
        -dPDFSETTINGS=/${3:-"screen"} \
        -dNOPAUSE -dQUIET -dBATCH \
        -dDownsampleColorImages=true \
        -dColorImageResolution=200 \
        -dColorImageDownsampleType=/Bicubic \
        -dDownsampleMonoImages=true \
        -dMonoImageResolution=700 \
        -dMonoImageDownsampleType=/Subsample \
        -dDownsampleGrayImages=true \
        -dGrayImageDownsampleType=/Bicubic \
        -dGrayImageResolution=150 \
        -dColorConversionStrategy=/RGB \
        -sOutputFile="$2" "$1"
}

if ! command -v gs &>/dev/null; then
    printf "%s\n" 'Error: Ghostscript (gs) is not installed.'
    return 1
fi

pdftrim "$@"