彩色图像到灰度转换 常见方法汇总与对比

import cv2 as cv
import numpy as np


def lut(weight):
    lut = []
    for i in range(256):
        lut.append(np.int32(i*weight))
    return np.array(lut)


def rgb2gray(image, type, blut=None, glut=None, rlut=None):
    h, w, c = image.shape
    gray = np.zeros((h,w), dtype=np.uint8)
    for row in range(h):
        for col in range(w):
            b, g, r = np.int32(image[row,col])
            if type == 1:
                y = blut[g] + glut[g] + rlut[r]
            if type == 2:
                y = (max([b, g, r]) + min([b, g,r])) // 2
            if type == 3:
                y = (b+g+r) // 3
            if type == 4:
                y = max([b, g, r])
            if type == 5:
                y = min([b, g, r])
            gray[row, col] = y

    return gray


if __name__ == "__main__":
    src = cv.imread("D:/images/flower.png")
    cv.imshow("input", src)
    gray1 = rgb2gray(src, 1, lut(0.299), lut(0.587), lut(0.114))
    gray2 = rgb2gray(src, 1, lut(0.21), lut(0.72), lut(0.07))
    gray3 = rgb2gray(src, 2)
    gray4 = rgb2gray(src, 3)
    gray5 = rgb2gray(src, 4)
    gray6 = rgb2gray(src, 5)

    cv.imshow("gray1", gray1)
    cv.imshow("gray2", gray2)
    cv.imshow("gray3", gray3)
    cv.imshow("gray4", gray4)
    cv.imshow("gray5", gray5)
    cv.imshow("gray6", gray6)

    cv.waitKey(0)
    cv.destroyAllWindows()