from pathlib import Path

import cv2 as cv
import numpy as np


input_path = Path("input/low-contrast.png")
output_dir = Path("output")
output_path = output_dir / "histogram-equalized.png"
clahe_path = output_dir / "histogram-clahe.png"
preview_path = output_dir / "histogram-equalize-preview.png"


def write_image(path, data):
    path.parent.mkdir(parents=True, exist_ok=True)
    if not cv.imwrite(str(path), data):
        raise SystemExit(f"Could not write {path}")


image = cv.imread(str(input_path), cv.IMREAD_GRAYSCALE)
if image is None:
    raise SystemExit(f"Could not read {input_path}")

equalized = cv.equalizeHist(image)

clahe = cv.createCLAHE(clipLimit=2.0, tileGridSize=(8, 8))
clahe_image = clahe.apply(image)

preview = np.hstack((image, equalized, clahe_image))
write_image(output_path, equalized)
write_image(clahe_path, clahe_image)
write_image(preview_path, preview)

print(f"input:     min={image.min():3d} max={image.max():3d} std={image.std():5.2f}")
print(f"equalized: min={equalized.min():3d} max={equalized.max():3d} std={equalized.std():5.2f}")
print(f"clahe:     min={clahe_image.min():3d} max={clahe_image.max():3d} std={clahe_image.std():5.2f}")
print(f"saved: {output_path}")
print(f"saved: {clahe_path}")
print(f"saved: {preview_path}")