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 "${@}"

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