Python图像运算之图像灰度非线性变换详解

# -*- coding: utf-8 -*-
# By：Eastmount
import cv2  
import numpy as np  
import matplotlib.pyplot as plt

#读取原始图像
img = cv2.imread('luo.png')

#图像灰度转换
grayImage = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

#获取图像高度和宽度
height = grayImage.shape[0]
width = grayImage.shape[1]

#创建一幅图像
result = np.zeros((height, width), np.uint8)

#图像灰度非线性变换：DB=DA×DA/255
for i in range(height):
    for j in range(width):
        gray = int(grayImage[i,j])*int(grayImage[i,j]) / 255
        result[i,j] = np.uint8(gray)

#显示图像
cv2.imshow("Gray Image", grayImage)
cv2.imshow("Result", result)

#等待显示
cv2.waitKey(0)
cv2.destroyAllWindows()

# -*- coding: utf-8 -*-
# By：Eastmount
import numpy as np
import matplotlib.pyplot as plt
import cv2

#绘制曲线
def log_plot(c):
    x = np.arange(0, 256, 0.01)
    y = c * np.log(1 + x)
    plt.plot(x, y, 'r', linewidth=1)
    plt.rcParams['font.sans-serif']=['SimHei'] #正常显示中文标签
    plt.title('对数变换函数')
    plt.xlabel('x')
    plt.ylabel('y')
    plt.xlim(0, 255), plt.ylim(0, 255)
    plt.show()

#对数变换
def log(c, img):
    output = c * np.log(1.0 + img)
    output = np.uint8(output + 0.5)
    return output

#读取原始图像
img = cv2.imread('dark.png')

#绘制对数变换曲线
log_plot(42)

#图像灰度对数变换
output = log(42, img)

#显示图像
cv2.imshow('Input', img)
cv2.imshow('Output', output)
cv2.waitKey(0)
cv2.destroyAllWindows()

# -*- coding: utf-8 -*-
# By：Eastmount
import numpy as np
import matplotlib.pyplot as plt
import cv2

#绘制曲线
def gamma_plot(c, v):
    x = np.arange(0, 256, 0.01)
    y = c*x**v
    plt.plot(x, y, 'r', linewidth=1)
    plt.rcParams['font.sans-serif']=['SimHei'] #正常显示中文标签
    plt.title('伽马变换函数')
    plt.xlabel('x')
    plt.ylabel('y')
    plt.xlim([0, 255]), plt.ylim([0, 255])
    plt.show()

#伽玛变换
def gamma(img, c, v):
    lut = np.zeros(256, dtype=np.float32)
    for i in range(256):
        lut[i] = c * i ** v
    output_img = cv2.LUT(img, lut) #像素灰度值的映射
    output_img = np.uint8(output_img+0.5)  
    return output_img

#读取原始图像
img = cv2.imread('white.png')

#绘制伽玛变换曲线
gamma_plot(0.00000005, 4.0)

#图像灰度伽玛变换
output = gamma(img, 0.00000005, 4.0)

#显示图像
cv2.imshow('Imput', img)
cv2.imshow('Output', output)
cv2.waitKey(0)
cv2.destroyAllWindows()