# Questions tagged [corners]

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### How to perform Spatial derivative calculation?

I'm trying to solve the following question about "Harris Corner Detection". Consider the following image: As the first step of the "Harris Corner Detection", we should compute the ...
• 293
134 views

### MATLAB code to detect the corners of an object without using the built in functions

I need to write a MATLAB code to detect the corners of an object in a black and white image without the built-in MATLAB vision toolbox or bwlabel, imrotate, imresize, corner, edge, reshape, imfilter,...
876 views

### Detecting corners using structure tensor matrix

How does eigenvalues of structure tensor matrix help in detecting corners? For eg, in Harris corner detection, we consider the matrix M = \sum_{w} w \cdot \begin{bmatrix} I_x^2 & I_x I_y \\ I_x ...
1 vote
165 views

### Corner detector vs feature detector

In the literature, I see "corner detector" and "feature detector" are interchangeably used for these methods e.g. Harris, Shi-Tomasi, FAST, etc. What is the difference between a ...
• 111
1 vote
373 views

### Understanding the Threshold Process in Harris Corner and Edge Detector

I have read the paper Chris Harris , Mike Stephens - A Combined Corner and Edge Detector about the Harris Corner and Edge Detector, but I didn't understand the point that after low and high threshold ...
• 167
481 views

### Given the 4 corners of two QR codes on a photographed sheet of paper, can we get a deskewed rectangular image?

I made a photo of 2 sheets of paper with a phone camera, each of them cropped at the: (x1, y1) top left corner of top QR code (x2, y2) bottom right corner of bottom QR code I hoped that the x, y ...
• 1,277
903 views

### Detect grid corner

I have a picture (B&W) of a curve which is plotted on a gridded paper. What I would like to do is to find the points which are corners of the grid. I apply Harris corner detection algorithm to ...
• 121
1 vote
105 views

### Moravec, Harris noisy window

Harris and Stephens writes about the interest window of Moravec: "The response is noisy because the window is binary and rectangular", and suggests applying a Gaussian window. My Question: ...
1 vote
3k views

### How to understand relationships between ellipse and second moment matrix of Harris corner detector?

guys. I am really lacking in knowledge of linear algebra. I am reading slides of Harris corner. But I am really confused about one of them. I know that I can find corners by two large eigenvalues but ...
• 145
1 vote
790 views

### Harris Corner Detection

In Harris Corner detection, is there any particular reason why this function is chosen: $R=det(M)-k*trace(M)^2$ We want to a function to evaluate how fast E(u,v) fluctuate accross different ...
• 223
380 views

### Keypoint detection with color images

Are there any known methods to use existing keypoint detectors (which generally work on grayscale images) on color images? of course, one could always add the results of the detector on all three ...
804 views

### Keypoint orientation with the oFAST from Rublee's ORB

I've just read the papers from Rublee et al. (ORB: an efﬁcient alternative to SIFT or SURF) and Rosten et al. (Machine learning for high-speed corner detection) (=fast-detector). Rublee tries to ...
• 231
156 views

### Filtering Corners Detected on Multiple Scales

I made a multi-scale Harris corner detector (inspired by MOPS) which is simply a Harris corner detector performed on several scales (i.e. subsampled versions of the same image). This effectively make ...
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