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import sys
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import cv2
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import numpy as np
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import matplotlib.pyplot as plt
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def linear_grayscale_transformation(img, a, b, c, d):
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ans = np.zeros((img.shape[0], img.shape[1]))
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for i in range(img.shape[0]):
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for j in range(img.shape[1]):
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if img[i][j] > b:
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ans[i][j] = d
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elif a <= img[i][j] <= b:
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ans[i][j] = (d - c) / (b - a) * (img[i][j] - a) + c
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else:
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ans[i][j] = c
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return ans / 255
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def linear_grayscale_transformation_threeChannel(img_path, a, b, c, d):
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img = cv2.imread(img_path, 1)
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img = np.array(img, dtype=np.float64)
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# 三个通道分别变换
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r = linear_grayscale_transformation(img[:, :, 0], a, b, c, d)
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g = linear_grayscale_transformation(img[:, :, 1], a, b, c, d)
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b = linear_grayscale_transformation(img[:, :, 2], a, b, c, d)
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# 三通道合并
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res = cv2.merge([r, g, b])
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res = res*255
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cv2.imwrite('./output/linear_grayscale_transformation.jpg', res)
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'''
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输入：一张图片，参数a,b,c,d
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输出：线性灰度变换的结果
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'''
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if __name__ == '__main__':
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linear_grayscale_transformation_threeChannel(sys.argv[1], eval(sys.argv[2]), eval(sys.argv[3]), eval(sys.argv[4]),
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eval(sys.argv[5]))
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