ImageMagick based command-line utility shell script to convert `png` to `jpg` with white background if having transparent background by default

png2jpg.sh

#!/bin/bash

# Function to print help message
function print_help() {
  app_name=${0##*/}
  echo "Syntax: $app_name <input_image> <output_image>"
  echo "  -h: Display this help message"
  echo "Usage: "
  echo "  $app_name input.png output.jpg"
  echo "  $app_name '*.png' output.jpg"
}

# Check if help flag is provided
if [[ "$1" == "-h" ]]; then
  print_help
  exit 0
fi

# Check if input file is provided
if [[ $# -lt 1 ]]; then
  echo "Error: Input file is required."
  print_help
  exit 1
fi

# Assign input and output files
input_file="$1"

# If output file is not provided, use input file name with output extension
if [[ $# -eq 1 ]]; then
  output_file="${input_file%.png}.jpg"
else
  output_file="$2"
fi

# Convert the image
convert "$input_file" -background white -alpha remove -alpha off "$output_file"

if [[ $? -ne 0 ]]; then
  echo "Error: Image conversion failed."
fi