filters.py

import cv2
import numpy as np
from registry import registry


@registry.register("Original")
def original(image):
    return image


@registry.register("Dot Effect", defaults={
    "dot_size": 10,
    "dot_spacing": 2,
    "invert": False,
}, min_vals={
    "dot_size": 1,
    "dot_spacing": 1,
}, max_vals={
    "dot_size": 20,
    "dot_spacing": 10,
}, step_vals={
    "dot_size": 1,
    "dot_spacing": 1,
})
def dot_effect(image, dot_size: int = 10, dot_spacing: int = 2, invert: bool = False):
    """
    ## Convert your image into a dotted pattern.

    **Args:**
    * `image` (numpy.ndarray): Input image (BGR or grayscale)
    * `dot_size` (int): Size of each dot
    * `dot_spacing` (int): Spacing between dots
    * `invert` (bool): Invert the dots

    **Returns:**
    * `numpy.ndarray`: Dotted image
    """
    # Convert to grayscale if image is color
    if len(image.shape) == 3:
        gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    else:
        gray = image

    # Apply adaptive thresholding to improve contrast
    gray = cv2.adaptiveThreshold(
        gray,
        255,
        cv2.ADAPTIVE_THRESH_GAUSSIAN_C,
        cv2.THRESH_BINARY,
        25,  # Block size
        5    # Constant subtracted from mean
    )

    height, width = gray.shape
    canvas = np.zeros_like(gray) if not invert else np.full_like(gray, 255)

    y_dots = range(0, height, dot_size + dot_spacing)
    x_dots = range(0, width, dot_size + dot_spacing)

    dot_color = 255 if not invert else 0
    for y in y_dots:
        for x in x_dots:
            region = gray[y:min(y+dot_size, height), x:min(x+dot_size, width)]
            if region.size > 0:
                brightness = np.mean(region)

            # Dynamic dot sizing based on brightness
            relative_brightness = brightness / 255.0
            if invert:
                relative_brightness = 1 - relative_brightness

            # Draw circle with size proportional to brightness
            radius = int((dot_size/2) * relative_brightness)
            if radius > 0:
                cv2.circle(canvas,
                           (x + dot_size//2, y + dot_size//2),
                           radius,
                           (dot_color),
                           -1)

    return canvas


@registry.register("Pixelize", defaults={
    "pixel_size": 10,
}, min_vals={
    "pixel_size": 1,
}, max_vals={
    "pixel_size": 50,
}, step_vals={
    "pixel_size": 1,
})
def pixelize(image, pixel_size: int = 10):
    """
    ## Apply a pixelization effect to the image.

    **Args:**
    * `image` (numpy.ndarray): Input image (BGR or grayscale)
    * `pixel_size` (int): Size of each pixel block

    **Returns:**
    * `numpy.ndarray`: Pixelized image
    """
    height, width = image.shape[:2]

    # Resize the image to a smaller size
    small_height = height // pixel_size
    small_width = width // pixel_size
    small_image = cv2.resize(
        image, (small_width, small_height), interpolation=cv2.INTER_LINEAR)

    # Resize back to the original size with nearest neighbor interpolation
    pixelized_image = cv2.resize(
        small_image, (width, height), interpolation=cv2.INTER_NEAREST)

    return pixelized_image


@registry.register("Sketch Effect", defaults={
    "blur_kernel_size": 21,
}, min_vals={
    "blur_kernel_size": 1,
}, max_vals={
    "blur_kernel_size": 51,
}, step_vals={
    "blur_kernel_size": 2,
})
def sketch_effect(image, blur_kernel_size: int = 21):
    """
    ## Apply a sketch effect to the image.

    **Args:**
    * `image` (numpy.ndarray): Input image (BGR or grayscale)
    * `blur_kernel_size` (int): Size of the Gaussian blur kernel (must be odd)

    **Returns:**
    * `numpy.ndarray`: Sketch effect applied image
    """
    # Ensure the kernel size is odd
    if blur_kernel_size % 2 == 0:
        blur_kernel_size += 1

    # Convert the image to grayscale
    if len(image.shape) == 3:
        gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    else:
        gray = image

    # Invert the grayscale image
    inverted_gray = cv2.bitwise_not(gray)

    # Apply Gaussian blur to the inverted image
    blurred = cv2.GaussianBlur(
        inverted_gray, (blur_kernel_size, blur_kernel_size), 0)

    # Blend the grayscale image with the blurred inverted image
    sketch = cv2.divide(gray, 255 - blurred, scale=256)

    return sketch