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import os
import numpy as np
from PIL import Image
from concurrent.futures import ThreadPoolExecutor
def create_gray_checkerboard(shape: tuple, square_size: int):
"""
Create a gray-scale checkerboard pattern array with the given shape.
The pattern alternates between 0.8 and 1.0 values in a square_size grid.
"""
# shape = (height, width)
x, y = np.meshgrid(np.arange(shape[1]), np.arange(shape[0]))
# Scale 0.2 + 0.8 => (0.2, 1.0) can also be used, but in this example we'll keep 0.8 and 1.0
# (depending on your desired brightness).
board = ((x // square_size + y // square_size) % 2) * 0.2 + 0.8
return board
def add_checkered_background_to_image(image_path, output_path, square_size=20):
"""
Add a gray checkerboard background to an image and save it as PNG.
"""
with Image.open(image_path) as img:
img = img.convert("RGBA")
# Create checkerboard pattern.
# Using the size (height, width) from the image.
checkerboard_array = create_gray_checkerboard((img.height, img.width), square_size)
# Convert checkerboard_array into an RGBA image (gray -> R=G=B, alpha=255)
# First convert float values into 8-bit grayscale.
# Expand dims to make it into (height, width, 1).
checkerboard_gray = (checkerboard_array * 255).astype(np.uint8)
checkerboard_gray = np.expand_dims(checkerboard_gray, axis=2)
# Stack 3 copies (for R,G,B) plus one alpha channel of 255.
alpha_channel = np.full_like(checkerboard_gray, 255)
checkerboard_rgba = np.concatenate([checkerboard_gray]*3 + [alpha_channel], axis=2)
background = Image.fromarray(checkerboard_rgba, mode="RGBA")
# Composite the image over the checkerboard background
combined = Image.alpha_composite(background, img)
combined.save(output_path, "PNG")
def process_image_file(input_path, output_path, square_size):
"""
Process a single image file to add a checkerboard background.
"""
if not os.path.exists(output_path):
add_checkered_background_to_image(input_path, output_path, square_size)
print(f"Processed (checkerboard): {input_path} -> {output_path}")
else:
print(f"Skipped (checkerboard): {output_path} already exists")
def process_directory(input_dir, output_dir, square_size=20):
"""
Recursively process a directory to add a checkerboard background to all images and convert them to PNG.
"""
if not os.path.exists(output_dir):
os.makedirs(output_dir)
tasks = []
with ThreadPoolExecutor() as executor:
for root, _, files in os.walk(input_dir):
for file in files:
if file.lower().endswith(('.png', '.jpg', '.jpeg', '.webp')):
input_path = os.path.join(root, file)
relative_path = os.path.relpath(input_path, input_dir)
output_path = os.path.join(output_dir, os.path.splitext(relative_path)[0] + '.png')
# Ensure the output directory exists
os.makedirs(os.path.dirname(output_path), exist_ok=True)
# Submit the task to the executor
tasks.append(executor.submit(process_image_file, input_path, output_path, square_size))
# Wait for all tasks to complete
for task in tasks:
task.result() |