PDF to PNG keep alpha

pdf_to_png.sh

#!/bin/bash

# brew install imagemagick ghostscript

# Check if an input file is provided
if [ $# -eq 0 ]; then
    echo "Usage: $0 input.pdf [output_basename]"
    exit 1
fi

# Define input and output file names
INPUT_PDF="$1"
OUTPUT_BASE="${2:-$(basename "$INPUT_PDF" .pdf)}"
HIGH_RES_TMP="${OUTPUT_BASE}-900dpi.png"

echo "Converting $INPUT_PDF to a high-resolution intermediate..."

# --- Create a single high-resolution image (900 DPI) ---
magick -density 900 "$INPUT_PDF" \
       -colorspace sRGB \
       -background transparent \
       -alpha on \
       -antialias \
       -filter Lanczos \
       -define pdf:use-cropbox=true \
       -quality 95 \
       PNG32:"$HIGH_RES_TMP"

# Check if the high-resolution image was created successfully
if [ ! -f "$HIGH_RES_TMP" ]; then
    echo "Error: Failed to create the high-resolution image."
    exit 1
fi

echo "Creating resized images..."

# --- Get the width of the 900 DPI image ---
WIDTH=$(magick identify -format "%w" "$HIGH_RES_TMP")

# --- Create smaller images by resizing the high-resolution one ---
magick "$HIGH_RES_TMP" -resize $((WIDTH * 150 / 900)) -quality 95 PNG32:"${OUTPUT_BASE}-1x.png"
magick "$HIGH_RES_TMP" -resize $((WIDTH * 300 / 900)) -quality 95 PNG32:"${OUTPUT_BASE}-2x.png"
magick "$HIGH_RES_TMP" -resize $((WIDTH * 450 / 900)) -quality 95 PNG32:"${OUTPUT_BASE}-3x.png"

# --- Clean up the large intermediate file ---
rm "$HIGH_RES_TMP"

echo "✓ Created: ${OUTPUT_BASE}-1x.png, ${OUTPUT_BASE}-2x.png, ${OUTPUT_BASE}-3x.png"

Usage:

find . -name "*.pdf" -print0 | xargs -0 -I {} ./pdf_to_png.sh "{}"