CODEWITHSUNDEEP
opencv
madan ram
madan ram

Reputation: 1270

corner detection using Chris Harris & Mike Stephens

I am not able to under stand the formula ,enter image description here

What is W (window) and intensity in the formula mean,

I found this formula in opencv doc http://docs.opencv.org/trunk/doc/py_tutorials/py_feature2d/py_features_harris/py_features_harris.html

Upvotes: 1

Views: 193

Answers (2)

skm
skm

Reputation: 5679

For a grayscale image, intensity levels (0-255) tells you how bright is the pixel..hope that you already know about it.

So, now the explanation of your formula is below:

Aim: We want to find those points which have maximum variation in terms of intensity level in all direction i.e. the points which are very unique in a given image.

I(x,y): This is the intensity value of the current pixel which you are processing at the moment.

I(x+u,y+v): This is the intensity of another pixel which lies at a distance of (u,v) from the current pixel (mentioned above) which is located at (x,y) with intensity I(x,y).

I(x+u,y+v) - I(x,y): This equation gives you the difference between the intensity levels of two pixels.

W(u,v): You don't compare the current pixel with any other pixel located at any random position. You prefer to compare the current pixel with its neighbors so you chose some value for "u" and "v" as you do in case of applying Gaussian mask/mean filter etc. So, basically w(u,v) represents the window in which you would like to compare the intensity of current pixel with its neighbors.

Upvotes: 4

Anoop K. Prabhu
Anoop K. Prabhu

Reputation: 5655

This link explains all your doubts.

For visualizing the algorithm, consider the window function as a BoxFilter, Ix as a Sobel derivative along x-axis and Iy as a Sobel derivative along y-axis.

http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/sobel_derivatives/sobel_derivatives.html will be useful to understand the final equations in the above pdf.

Upvotes: 2

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