Red-Gray image filter (a.k.a. "Apple-nize" filter)

redgray.py

#!/usr/bin/env python3
import cv2
import numpy as np
import sys


def hsv_mask(hsv, h_center, h_range, s_low, v_low):
    h_low = (h_center - h_range) % 180
    h_high = (h_center + h_range) % 180
    h, s, v = cv2.split(hsv)
    kernel = np.ones((3,3), np.uint8)
    # Hue mask
    if h_low > h_high:
        _, m1 = cv2.threshold(h, h_low,  255, cv2.THRESH_BINARY)
        _, m2 = cv2.threshold(h, h_high, 255, cv2.THRESH_BINARY_INV)
        mask = cv2.bitwise_or(m1, m2)
    else:
        _, acc = cv2.threshold(h,   h_low,  255, cv2.THRESH_TOZERO)
        _, acc = cv2.threshold(acc, h_high, 255, cv2.THRESH_TOZERO_INV)
        _, mask = cv2.threshold(acc, 0, 255, cv2.THRESH_BINARY)
    mask = cv2.morphologyEx(mask, cv2.MORPH_CLOSE, kernel, iterations=2)
    # Saturation mask
    _, s_mask = cv2.threshold(s, s_low, 255, cv2.THRESH_BINARY)
    s_mask = cv2.morphologyEx(s_mask, cv2.MORPH_CLOSE, kernel)
    # Value(Brightness) mask
    _, v_mask = cv2.threshold(v, v_low, 255, cv2.THRESH_BINARY)
    v_mask = cv2.morphologyEx(v_mask, cv2.MORPH_CLOSE, kernel)
    mask = cv2.bitwise_and(mask, s_mask)
    mask = cv2.bitwise_and(mask, v_mask)
    mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel)
    return mask


def convert(infile, outfile):
    src = cv2.imread(infile)
    hsv = cv2.cvtColor(src, cv2.COLOR_BGR2HSV)
    mask = hsv_mask(hsv, 10, 30, 64, 64)
    #cv2.imshow("mask", mask)
    hsv[:,:,1] = cv2.bitwise_and(hsv[:,:,1], hsv[:,:,1], mask=mask)
    img = cv2.cvtColor(hsv, cv2.COLOR_HSV2BGR)
    if outfile:
        cv2.imwrite(outfile, img)
    else:
        cv2.imshow("Preview (press ESC to exit)", img)
        while cv2.waitKey(33) != 27:
            pass


if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("usage: {} <infile> [<outfile>]\n".format(__file__))
        sys.exit(0)
    convert(sys.argv[1], sys.argv[2] if 2 < len(sys.argv) else None)

http://qiita.com/yohhoy/items/2176a9d8894adfb6abc7 (ja)