Harris角点检测

以你之姓@ 2023-01-11 01:16 199阅读 0赞

Harris实现过程：

计算图像在X和Y方向的梯度：

![I\_\{x\}=\\partial I/\\partial x=I\\bigotimes \\begin\{pmatrix\} -1 & 0 & 1 \\end\{pmatrix\}; I\_\{y\}=\\partial I/\\partial y=I\\bigotimes\\begin\{pmatrix\} -1 & 0 & 1 \\end\{pmatrix\}^\{T\}][I_x_partial I_partial x_I_bigotimes _begin_pmatrix_ -1 _ 0 _ 1 _end_pmatrix_ I_y_partial I_partial y_I_bigotimes_begin_pmatrix_ -1 _ 0 _ 1 _end_pmatrix_T]

计算图像两个方向梯度的乘积

![I\_\{x\}^\{2\}=I\_\{x\}\\cdot I\_\{x\},I\_\{y\}^\{2\}=I\_\{y\}\\cdot I\_\{y\},I\_\{xy\}^\{2\}=I\_\{x\}\\cdot I\_\{y\}][I_x_2_I_x_cdot I_x_I_y_2_I_y_cdot I_y_I_xy_2_I_x_cdot I_y]

使用高斯函数对三者进行高斯加权，生成矩阵M的A，B，C；

![A=g(I\_\{x\}^\{2\})=I\_\{x\}^\{2\}\\bigotimes \\omega ; C=g(I\_\{y\}^\{2\})=I\_\{y\}^\{2\}\\bigotimes \\omega ; B=g(I\_\{xy\})=I\_\{xy\}\\bigotimes \\omega ;][A_g_I_x_2_I_x_2_bigotimes _omega _ C_g_I_y_2_I_y_2_bigotimes _omega _ B_g_I_xy_I_xy_bigotimes _omega]

计算每个像素的Harris相应值R，并对小于某一阈值t的R置为零；

在3\*3或者5\*5邻域内进行非最大值抑制，局部最大值点即为图像中的角点。

**cv2.cornerHarris()参数如下：**

img-数据类型为float32的输入图像

blocksize-角点检测中的领域大小

ksize-Sobel求导中使用的窗口大小

k-Harris角点检测方程中的自由参数，取值参数为\[0.04,0.06\]

import cv2
    import numpy as np
    
    img = cv2.imread('test5.jpg')
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    gray = np.float32(gray)
    #输入图像必须是float32,最后的一个参数在0.04到0.06之间
    dst = cv2.cornerHarris(gray,2,3,0.03)
    #结果进行膨胀，可有可无
    dst = cv2.dilate(dst,None)
    print(dst)
    #设定阈值，不同图像阈值不同
    img[dst>0.01*dst.max()]=[0,0,255]
    print(dst.max())
    cv2.imshow('dst_img',img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

参数为0.03和0.06时候的结果比较。。。。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 3][]

SIFT代码：

import cv2
    import numpy as np
    img = cv2.imread('test.jpg')
    gray =cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    sift = cv2.xfeatures2d.SIFT_create()
    kp = sift.detecgt(gray,None)
    img = cv2.drawKeyPoints(gray,kp,img)
    cv2.imshow('sp',img)
    cv2.waitKey()
    #需要最新的才可以执行

[I_x_partial I_partial x_I_bigotimes _begin_pmatrix_ -1 _ 0 _ 1 _end_pmatrix_ I_y_partial I_partial y_I_bigotimes_begin_pmatrix_ -1 _ 0 _ 1 _end_pmatrix_T]: https://private.codecogs.com/gif.latex?%5Cfn_cm%20I_%7Bx%7D%3D%5Cpartial%20I/%5Cpartial%20x%3DI%5Cbigotimes%20%5Cbegin%7Bpmatrix%7D%20-1%20%26%200%20%26%201%20%5Cend%7Bpmatrix%7D%3B%20I_%7By%7D%3D%5Cpartial%20I/%5Cpartial%20y%3DI%5Cbigotimes%5Cbegin%7Bpmatrix%7D%20-1%20%26%200%20%26%201%20%5Cend%7Bpmatrix%7D%5E%7BT%7D
[I_x_2_I_x_cdot I_x_I_y_2_I_y_cdot I_y_I_xy_2_I_x_cdot I_y]: https://private.codecogs.com/gif.latex?%5Cfn_cm%20I_%7Bx%7D%5E%7B2%7D%3DI_%7Bx%7D%5Ccdot%20I_%7Bx%7D%2CI_%7By%7D%5E%7B2%7D%3DI_%7By%7D%5Ccdot%20I_%7By%7D%2CI_%7Bxy%7D%5E%7B2%7D%3DI_%7Bx%7D%5Ccdot%20I_%7By%7D
[A_g_I_x_2_I_x_2_bigotimes _omega _ C_g_I_y_2_I_y_2_bigotimes _omega _ B_g_I_xy_I_xy_bigotimes _omega]: https://private.codecogs.com/gif.latex?%5Cfn_cm%20A%3Dg%28I_%7Bx%7D%5E%7B2%7D%29%3DI_%7Bx%7D%5E%7B2%7D%5Cbigotimes%20%5Comega%20%3B%20C%3Dg%28I_%7By%7D%5E%7B2%7D%29%3DI_%7By%7D%5E%7B2%7D%5Cbigotimes%20%5Comega%20%3B%20B%3Dg%28I_%7Bxy%7D%29%3DI_%7Bxy%7D%5Cbigotimes%20%5Comega%20%3B
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/2021012516321114.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210125164035805.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20210125163747566.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4=,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20210125163630623.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dpbmdneW4=,size_16,color_FFFFFF,t_70