From 6105a92ad9298971eb727dcb2dab91d005b6c7c2 Mon Sep 17 00:00:00 2001
From: GreatestCapacity <greatest_capacity@mail.com>
Date: Sun, 12 May 2019 03:11:22 +0800
Subject: [PATCH 1/3] Add Harris feature detector

---
 .../feature_detectors/README.md               | 20 +++++++++++
 .../feature_detectors/harris.py               | 35 +++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 digital_image_processing/feature_detectors/README.md
 create mode 100644 digital_image_processing/feature_detectors/harris.py

diff --git a/digital_image_processing/feature_detectors/README.md b/digital_image_processing/feature_detectors/README.md
new file mode 100644
index 000000000000..a00b88865efb
--- /dev/null
+++ b/digital_image_processing/feature_detectors/README.md
@@ -0,0 +1,20 @@
+# Computation of Harris Detector
+
+## Dependencies
+
+- opencv-python
+- Numpy
+- Scipy
+
+## Steps
+
+Given image $I$, $n\times n$ size Gaussian Kernel $G_{n\times n}$,
+
+1. Compute the gradients of the image, both horizontal and vertical directions. $X=(-1, 0, 1)\otimes I​$, $Y=(-1, 0, 1)^T \otimes I​$
+2. Compute the matrix $M$, where $A = G_{n\times n} \otimes X^2$, $B=G_{n\times n}\otimes Y^2$, $C=G_{n\times n}\otimes XY$
+3. Compute the response function $R​$, where $R=AB-C^2-k(A+B)​$
+4. Classify all points in $R​$.
+
+## Reference
+
+C. Harris and M. Stephens, “A Combined Corner and Edge Detector,” in Procedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
\ No newline at end of file
diff --git a/digital_image_processing/feature_detectors/harris.py b/digital_image_processing/feature_detectors/harris.py
new file mode 100644
index 000000000000..0319b0873b5a
--- /dev/null
+++ b/digital_image_processing/feature_detectors/harris.py
@@ -0,0 +1,35 @@
+"""
+Implementation of Harris Detector
+
+Reference:
+C. Harris and M. Stephens, “A Combined Corner and Edge Detector,”
+in Procedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
+"""
+
+import cv2 as cv
+import numpy as np
+from scipy.signal import convolve2d
+
+# Read original image and get gaussian kernel
+img = cv.imread('example.png')
+img_gray = cv.cvtColor(img, cv.COLOR_RGB2GRAY)
+
+G = cv.getGaussianKernel(3, 1)
+
+# Begin Harris Detector Computation
+
+I = img_gray.astype('float32')
+X = convolve2d(I, [[-1, 0, 1]], mode='same')
+Y = convolve2d(I, [[-1], [0], [1]], mode='same')
+A = convolve2d(X*X, G, mode='same')
+B = convolve2d(Y*Y, G, mode='same')
+C = convolve2d(X*Y, G, mode='same')
+R = A*B - C*C - 0.04 * (A + B)
+
+# Finished Harris Detector Computation
+
+# Classify all points in R and show corners in image
+maxima = np.max(R)
+img[R > maxima*0.1] = [255, 0, 0]
+cv.imshow('harris_detector', img)
+cv.waitKey(0)

From 1c6321189222dc72c203bb72022a2c5ea02e4cae Mon Sep 17 00:00:00 2001
From: GreatestCapacity <greatest_capacity@mail.com>
Date: Sun, 12 May 2019 03:14:03 +0800
Subject: [PATCH 2/3] Add Harris feature detector

---
 digital_image_processing/feature_detectors/harris.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/digital_image_processing/feature_detectors/harris.py b/digital_image_processing/feature_detectors/harris.py
index 0319b0873b5a..81d0cd4731ba 100644
--- a/digital_image_processing/feature_detectors/harris.py
+++ b/digital_image_processing/feature_detectors/harris.py
@@ -12,7 +12,7 @@
 
 # Read original image and get gaussian kernel
 img = cv.imread('example.png')
-img_gray = cv.cvtColor(img, cv.COLOR_RGB2GRAY)
+img_gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
 
 G = cv.getGaussianKernel(3, 1)
 

From 9655961a41f68d3fde6ccd6c127665eb926dc507 Mon Sep 17 00:00:00 2001
From: GreatestCapacity <greatest_capacity@mail.com>
Date: Sun, 12 May 2019 03:26:49 +0800
Subject: [PATCH 3/3] Add Harris feature detector

---
 digital_image_processing/feature_detectors/README.md | 2 +-
 digital_image_processing/feature_detectors/harris.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/digital_image_processing/feature_detectors/README.md b/digital_image_processing/feature_detectors/README.md
index a00b88865efb..eea71b6ee5ec 100644
--- a/digital_image_processing/feature_detectors/README.md
+++ b/digital_image_processing/feature_detectors/README.md
@@ -17,4 +17,4 @@ Given image $I$, $n\times n$ size Gaussian Kernel $G_{n\times n}$,
 
 ## Reference
 
-C. Harris and M. Stephens, “A Combined Corner and Edge Detector,” in Procedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
\ No newline at end of file
+C. Harris and M. Stephens, “A Combined Corner and Edge Detector,” in Proceedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
\ No newline at end of file
diff --git a/digital_image_processing/feature_detectors/harris.py b/digital_image_processing/feature_detectors/harris.py
index 81d0cd4731ba..b7ff231c1107 100644
--- a/digital_image_processing/feature_detectors/harris.py
+++ b/digital_image_processing/feature_detectors/harris.py
@@ -3,7 +3,7 @@
 
 Reference:
 C. Harris and M. Stephens, “A Combined Corner and Edge Detector,”
-in Procedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
+in Proceedings of Alvey Vision Conference 1988, Manchester, 1988, pp. 23.1-23.6.
 """
 
 import cv2 as cv