image crop tool

README.md

Here is the prompt I used in VSCode Agent mode on April 12, 2025

make a bash script in this file that follows the best practices from https://bertvv.github.io/cheat-sheets/Bash.html #fetch .
The bash script should use the convert tool from the ImageMagick program to process the input image and create an output image.
Give a helpful error message if the convert tool is not available, with instructions for common ways to install the program 
with homebrew or apt. The script should take a single argument as the source image, and create an output file that is named
the same as the source image but with "-output" added as a suffix to the basename of the input file. Keep the output file
extension the same as the input file extension. Validate that the input file is a valid PNG file with 1920x1080 dimensions.
The processing of the image should be to -crop the image starting at Y coordinate offset pixel 1304 and continuing to
Y-coordinate pixel 1080. The X coordinate offset should be zero, and the xcoordinate end point should be 1920.

create-bottom-bar.sh is the script that it created.

create-bottom-bar.sh

#!/usr/bin/env bash

# Script to crop an input image using ImageMagick's convert tool
# Creates an output image named after the input with "-output" suffix
# The script crops from Y coordinate 1034 to 1080, and X from 0 to 1920

# Here is the prompt I used with VSCode agent mode on April 12, 2025
# running against Claude 3.7 Sonnet
# make a bash script in this file that follows the best practices from
# https://bertvv.github.io/cheat-sheets/Bash.html #fetch . The bash script should
# use the convert tool from the ImageMagick program to process the input image and
# create an output image. Give a helpful error message if the convert tool is not
# available, with instructions for common ways to install the program with homebrew
# or apt. The script should take a single argument as the source image, and create
# an output file that is named the same as the source image but with "-output"
# added as a suffix to the basename of the input file. Keep the output file
# extension the same as the input file extension. Validate that the input file is a
# valid PNG file with 1920x1080 dimensions. The processing of the image should be
# to -crop the image starting at Y coordinate offset pixel 1034 and continuing to
# Y-coordinate pixel 1080. The X coordinate offset should be zero, and the
# xcoordinate end point should be 1920.

set -o errexit  # abort on nonzero exit status
set -o nounset  # abort on unbound variable
set -o pipefail # don't hide errors within pipes

# Function for error messages
error() {
  printf "\033[0;31m!!! %s\033[0m\n" "${*}" 1>&2
}

# Function for success messages
success() {
  printf "\033[0;32m=== %s\033[0m\n" "${*}"
}

# Function for info messages
info() {
  printf "\033[0;34m--- %s\033[0m\n" "${*}"
}

# Function to check if ImageMagick is installed
check_imagemagick() {
  if ! command -v magick > /dev/null 2>&1; then
    error "ImageMagick 'magick' tool not found!"
    printf "Please install ImageMagick using one of these methods:\n\n"
    printf "  • macOS (Homebrew): brew install imagemagick\n"
    printf "  • Ubuntu/Debian: sudo apt update && sudo apt install -y imagemagick\n"
    printf "  • CentOS/RHEL: sudo yum install -y imagemagick\n"
    printf "  • Windows: Download from https://imagemagick.org/script/download.php\n"
    exit 1
  fi
}

# Function to display usage information
usage() {
  cat << HELPMSG
Usage: $(basename "${0}") [IMAGE_FILE]

Process a PNG image (1920x1080) by cropping to keep just the bottom portion.
Creates an output file with "-output" added to the original filename.

Example: $(basename "${0}") my-image.png
         This will create my-image-output.png
HELPMSG
}

# Function to validate the input image
validate_image() {
  local image_file="${1}"

  # Check if file exists
  if [[ ! -f "${image_file}" ]]; then
    error "Input file does not exist: ${image_file}"
    exit 1
  fi

  # Get image dimensions and type using identify
  local dimensions
  dimensions=$(identify -format "%w %h %m" "${image_file}" 2>/dev/null) || {
    error "Failed to identify image. Is it a valid image file?"
    exit 1
  }

  # Parse dimensions and type
  local width height type
  read -r width height type <<< "${dimensions}"

  # Check if image is PNG
  if [[ "${type}" != "PNG" ]]; then
    error "Input file must be a PNG image. Found: ${type}"
    exit 1
  fi

  # Check dimensions
  if [[ "${width}" -ne 1920 || "${height}" -ne 1080 ]]; then
    error "Input image must be 1920x1080 pixels. Found: ${width}x${height}"
    exit 1
  fi
}

# Main function to process the image
process_image() {
  local input_file="${1}"
  local base_name extension output_file

  # Extract filename and extension
  extension="${input_file##*.}"
  base_name="$(basename "${input_file}" ".${extension}")"
  output_file="${base_name}-output.${extension}"

  info "Processing image: ${input_file}"
  info "Output will be saved as: ${output_file}"

  # Calculate crop height: Y from 1034 to 1080 means a height of (1080-1034) pixels
  local crop_height=$((1080 - 1034))

  # Process image using magick convert
  # Starting at x=0, y=1034 and keeping width=1920, height=224 pixels
  magick "${input_file}" -crop "1920x${crop_height}+0+1034" "${output_file}" || {
    error "Failed to process the image."
    exit 1
  }

  success "Image processing completed successfully!"
  success "Output saved as: ${output_file}"
}

# Main execution
main() {
  # Check for help argument
  if [[ $# -eq 0 || "${1-}" == "--help" || "${1-}" == "-h" ]]; then
    usage
    exit 0
  fi

  # Check if ImageMagick is installed
  check_imagemagick

  # Validate and process the image
  validate_image "${1}"
  process_image "${1}"
}

# Execute main function
main "${@}"

edited to fix a typo that flowed through from my instructions. I had meant to say crop from 1034, and said 1304 instead.

also changed from the convert command to the magick command because ImageMagick was printing warnings about deprecation and saying to use magick instead.