1、灰度拉伸是一种简单的线性运算。经过变换后使得灰度布满整个灰度等级范围。为了把不同图像的灰度值映射到0-255范围内，常见的方法有：
2、处理过程如下：import cv2 as cvimport numpy as npfrom matplotlib import pyplot as pltimage = cv.imread('c:\\meiping1.png')imgGray = cv.cvtColor(image, cv.COLOR_RGB2GRAY)cv.imshow('imgGray', imgGray)
3、rows, cols = imgGray.shapereshapeGray = imgGray.reshape(rows * cols)print(reshapeGray)reshapeGrayList = reshapeGray.tolist()通过.tolist() 转换成列表 方便后面求最大灰度 和最小灰度
4、A = min(reshapeGrayList)B = max(reshapeGrayList)1)方法一Gxy = (255 / (B - A)) * abs(imgGray - A)print('A = %d,B = %d' % (A, B))
5、2）另一种方法MAX = 255MIN = 0Gxy = (imgGray - A) / (B - A) * (MAX - MIN) + MIN区别在gxy 其他不变！
6、result = np.uint8(Gxy )cv.imshow('imgGray', imgGray)print(imgGray)cv.imshow('result', result)hist = cv.calcHist([imgGray], [0], None, [256], [0.0,255.0])hist1 = cv.calcHist([result], [0], None, [256], [0.0,255.0])plt.plot(hist)plt.show()plt.plot(hist1)plt.show()cv.waitKey()cv.destroyAllWindows()
7、小结：1）2种方法原始图和结果图对比基本亮度或者对比度提高了。图片更便于辨识度提高。2）直方图也类似的。3）灰度转一维列表 tolist()
