Python script to make white pixels transparent

make_white_pixels_transparent.py

import sys
import argparse
from PIL import Image
import numpy as np

def add_transparency(input_path, output_path, threshold=240):
    """
    Add alpha channel to an image based on brightness threshold.
    Makes pixels with brightness >= threshold transparent.

    Args:
        input_path (str): Path to input image
        output_path (str): Path to save output image
        threshold (int): Brightness threshold (0-255), pixels >= this value become transparent
    """
    try:
        # Open the image
        img = Image.open(input_path)

        # Convert to RGBA if not already
        if img.mode != 'RGBA':
            img = img.convert('RGBA')

        # Convert to numpy array for easier manipulation
        data = np.array(img)

        # Calculate brightness (average of RGB channels)
        # Using a simple average: (R + G + B) / 3
        r, g, b, a = data[:,:,0], data[:,:,1], data[:,:,2], data[:,:,3]
        brightness = (r.astype(int) + g.astype(int) + b.astype(int)) // 3

        # Create mask where brightness >= threshold
        mask = brightness >= threshold

        # Set alpha channel to 0 (transparent) where mask is True
        data[:,:,3] = np.where(mask, 0, 255)

        # Create new image from modified array
        result = Image.fromarray(data)

        # Save the result
        result.save(output_path)
        print(f"Successfully created transparent image at: {output_path}")
        return True

    except Exception as e:
        print(f"Error processing image: {e}")
        return False

def main():
    parser = argparse.ArgumentParser(description='Add transparency to an image based on brightness.')
    parser.add_argument('input', help='Input image file path')
    parser.add_argument('output', help='Output image file path')
    parser.add_argument('-t', '--threshold', type=int, default=240,
                        help='Brightness threshold (0-255). Pixels with brightness >= threshold become transparent. Default: 240')

    args = parser.parse_args()

    add_transparency(args.input, args.output, args.threshold)

if __name__ == "__main__":
    main()

(This is what the processed output looks like, when alpha channels are visualized!)