【Python】OpenCV库学习笔记（五）

超、凢脫俗 2023-01-08 03:27 160阅读 0赞

### OpenCV库学习笔记（五） ###

*  1. 图像直方图（histogram）
 *   *  1.1 绘制图片直方图
     *  1.2 RGB三通道的直方图
     *  1.3 直方图应用1
     *  1.4 直方图应用2
 *  2. 直方图反向投影
 *   *  2.1 黑白2D直方图
     *  2.2 彩色2D直方图
     *  2.3 直方图反向衍射

# 1. 图像直方图（histogram） #

## 1.1 绘制图片直方图 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    
    def plot_demo(image):
        pyplot.hist(image.ravel(), 256, [0, 256])
        pyplot.show()
    
    
    image = cv.imread("01.jpg")
    cv.namedWindow("image", cv.WINDOW_AUTOSIZE)
    cv.imshow("image", image)
    plot_demo(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70]

## 1.2 RGB三通道的直方图 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    def image_hist(image):
        color = ('blue', 'green', 'red')
        for i, color in  enumerate(color):
            hist = cv.calcHist([image], [i], None, [256], [0,256])
            pyplot.plot(hist, color=color)
            pyplot.xlim([0, 256])
        pyplot.show()
    
    image = cv.imread("01.jpg")
    cv.namedWindow("image", cv.WINDOW_AUTOSIZE)
    cv.imshow("image", image)
    image_hist(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 1]

## 1.3 直方图应用1 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    def equalHist_demo(image):
        gray = cv.cvtColor(image, cv.COLOR_BGR2GRAY)
        dst = cv.equalizeHist(gray)
        cv.imshow("equalHist_demo", dst)hg
    
    image = cv.imread("01.jpg")
    cv.namedWindow("image", cv.WINDOW_AUTOSIZE)
    cv.imshow("image", image)
    equalHist_demo(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 2]

## 1.4 直方图应用2 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    
    def Clahe_demo(image):
        gray = cv.cvtColor(image, cv.COLOR_BGR2GRAY)
        clahe = cv.createCLAHE(clipLimit=5.0, tileGridSize=(8, 8))
        dst = clahe.apply(gray)
        cv.imshow("Clahe_demo", dst)
    
    image = cv.imread("01.jpg")
    cv.namedWindow("image", cv.WINDOW_AUTOSIZE)
    cv.imshow("image", image)
    Clahe_demo(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 3]

# 2. 直方图反向投影 #

## 2.1 黑白2D直方图 ##

import cv2 as cv
    import numpy
    
    
    
    def hist2d_demo(image):
        hsv = cv.cvtColor(image, cv.COLOR_BGR2HSV)
        hist = cv.calcHist([image], [0, 1], None, [100, 250], [0, 100, 0, 256])
        cv.imshow("hist2D", hist)
    
    
    image = cv.imread("01.jpg")
    cv.namedWindow("input image", cv.WINDOW_AUTOSIZE)
    cv.imshow("input image", image)
    hist2d_demo(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 4]

## 2.2 彩色2D直方图 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    
    def hist2d_demo(image):
        hsv = cv.cvtColor(image, cv.COLOR_BGR2HSV)
        hist = cv.calcHist([image], [0, 1], None, [100, 250], [0, 100, 0, 256])
        pyplot.imshow(hist, interpolation='nearest')
        pyplot.title("2D Histogram")
        pyplot.show()
    
    
    image = cv.imread("01.jpg")
    cv.namedWindow("input image", cv.WINDOW_AUTOSIZE)
    cv.imshow("input image", image)
    hist2d_demo(image)
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 5]

## 2.3 直方图反向衍射 ##

import cv2 as cv
    import numpy
    from matplotlib import pyplot
    
    def back_projection_demo():
        target = cv.imread("01.jpg")
        sample = cv.imread("sample.jpg")
        sam_hsv = cv.cvtColor(sample, cv.COLOR_BGR2HSV)
        tar_hsv = cv.cvtColor(target, cv.COLOR_BGR2HSV)
    
        # 展示图片
        cv.imshow("target", target)
        cv.imshow("sample", sample)
    
        sam_hist = cv.calcHist([sam_hsv], [0, 1], None, [36, 48], [0, 100, 0, 256])
        cv.normalize(sam_hsv, sam_hsv, 0, 255, cv.NORM_MINMAX)
        dst = cv.calcBackProject([tar_hsv], [0, 1], sam_hist, [0, 100, 0, 256], 1)
        cv.imshow("BackProjectionDemo", dst)
    
    back_projection_demo()
    cv.waitKey(0)
    cv.destroyAllWindows()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTQzNzAyMg_size_16_color_FFFFFF_t_70 6]

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