## Die Suche ergab 70 Treffer

19. Aug 2013 20:30
Forum: Computer Vision
Thema: HOG - What's the point of blocks?
Antworten: 3
Zugriffe: 1827

### Re: HOG - What's the point of blocks?

Each cell contibutes multiple times, namly once for each normalization as part of the various blocks. So take your first one, but normalize all the h's w.r.t. to the block they came from.
19. Aug 2013 16:49
Forum: Computer Vision
Thema: Eigenvalues & eigenvectors
Antworten: 2
Zugriffe: 915

### Re: Eigenvalues & eigenvectors

If you are worried just write down the equations for 2x2 eigenvectors/eigenvalues. It's not really heavy maths..
19. Aug 2013 16:46
Forum: Computer Vision
Thema: HOG - What's the point of blocks?
Antworten: 3
Zugriffe: 1827

### Re: HOG - What's the point of blocks?

Well, you do not just concatenate those cells, but you normalize within each block. The benefit is invariance to illumination and contrast.
19. Aug 2013 16:43
Forum: Computer Vision
Thema: What's the sum in the structure tensor
Antworten: 2
Zugriffe: 876

### Re: What's the sum in the structure tensor

Hi again, in the slides (l9 p. 44, l5 p. 68) the structure tensor is denoted as H = \sum\limits_{x,y \in R} \begin{pmatrix} I_x(x,y)^2 & I_x(x,y) I_y(x,y) \\ I_x(x,y) I_y(x,y) & I_y(x,y)^2\end{pmatrix} In praxis I always calculated the structure tensor for a single pixel (x,y) without summarizing a...
14. Aug 2013 17:18
Forum: Computer Vision
Thema: Rank of a Homography (Sample Solution to Assignment 4)
Antworten: 4
Zugriffe: 1539

### Re: Rank of a Homography (Sample Solution to Assignment 4)

Problem 3.
14. Aug 2013 16:00
Forum: Computer Vision
Thema: Rank of a Homography (Sample Solution to Assignment 4)
Antworten: 4
Zugriffe: 1539

### Re: Rank of a Homography (Sample Solution to Assignment 4)

That was basically my point, yes.
14. Aug 2013 12:37
Forum: Computer Vision
Thema: Rank of a Homography (Sample Solution to Assignment 4)
Antworten: 4
Zugriffe: 1539

### Rank of a Homography (Sample Solution to Assignment 4)

Hi there, just want to mention something odd about the sample solution to assignment 4. That is, when the homography has been computed, a rank of 2 is enforced. To my knowledge that is pretty conterproductive as a homography with a rank of 2 is no one-to-one mapping anymore. Furthermore, if you enfo...
24. Jul 2013 07:46
Forum: Computer Vision
Antworten: 1
Zugriffe: 759

Say, does anybody know when the announced questions & answers session will take place? Can't remember to hear an exact date or I just forgot. Thx!
19. Jul 2013 12:42
Forum: Computer Vision
Thema: Estimating iterations and match quality
Antworten: 1
Zugriffe: 1066

### Re: Estimating iterations and match quality

The formula from l10 slide 26 is pretty simple of course, but how do we get the probability of an inlier? Do we have to guess it completely random? That's right. Just take a guess. It doesn't matter that much though, after all it's just about computing a reasonable number of iterations that is good...
17. Jul 2013 17:06
Forum: Computer Vision
Thema: Panorama creation
Antworten: 8
Zugriffe: 2157

### Re: Panorama creation

Is your first picture the img_right right after you transformed it? Do you apply the transformation directly to the image? Yes, it is the right image after transformation obtained by using interp2 together with the transformed coordinates. There is no cropping step involved in creating this transfo...
16. Jul 2013 16:05
Forum: Computer Vision
Thema: Panorama creation
Antworten: 8
Zugriffe: 2157

### Re: Panorama creation

What do you guys mean by small gap? How small exactly? I assume it's normal that the resulting stitch is not always 'perfect' down to epsilon.. does it kinda look like this?
15. Jul 2013 15:56
Forum: Computer Vision
Thema: Panorama creation
Antworten: 8
Zugriffe: 2157

### Re: Panorama creation

Hi, the task says "The rest part of the panorama image should be reconstructed from transformed a4p3b.png.". I wanted to ask what we are aspected to do (to get all points ^^) ? It is sufficient to implement a simple method which copies the transformend image into the panorama (so that it looks nice...
15. Jul 2013 15:54
Forum: Computer Vision
Thema: How to estimate the homography matrix
Antworten: 4
Zugriffe: 1869

### Re: How to estimate the homography matrix

I don't take samples with rank < 3. However, if tH has rank 3 it can occur that the uncodinitioned matrix H has rank<3. So I require that both matrices have rank 3. Just check the condition number of the untransformed homography (in the conditioned space if you want). I guess homographies often res...
14. Jul 2013 16:56
Forum: Computer Vision
Thema: How to estimate the homography matrix
Antworten: 4
Zugriffe: 1869

### Re: How to estimate the homography matrix

Hi! I think your problem is the following: In the RANSAC step you should definitely discard certain samples that are too close to singularity because they just ill-posed samples. You can see that by subtracting your points from each other: p1=[ 369 385 361 248 204 201 220 251 ]; p2=[ 171 185 163 47 ...
13. Jul 2013 22:54
Forum: Computer Vision
Thema: A4 Problem 2
Antworten: 1
Zugriffe: 874

### Re: A4 Problem 2

1. I tried to build my preliminary F with all right-value columns where the corresponding singular value is really close to 0 (so that matlab actually displays 0). What are you trying to say? Building F means doing a SVD on the system matrix A as shown on page 75 of the l10-geometry slides with F b...