Questions tagged [homography]

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Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers

I have been working on the topic of camera pose estimation for augmented reality and visual tracking applications for a while and I think that although there is a lot of detailed information on the ...
8k views

Calculating a homography based on detected lines

I know you can calculate homographies from image to camera plane using correspondence points between a "perfect model" and the image points. I'm doing it for a football pitch/field, and have used ...
10k views

Why normalize the data set before applying Direct Linear Transform

Direct Linear Transform (DLT for short) is a method of homography estimation, it solves the overdetermined linear system via SVD $$Ah=b$$to find a solution $h$ under constraint $\|h\|=1$. Actually it ...
4k views

Filtering RANSAC Estimated Homographies

I am using RANSAC algorithm for homography estimation between pairs of images taken with cameras which do not have any translation between them (pure rotation and change of scale/zoom). It works well ...
6k views

What is the link between the homography computed over 2 images and the homography computed over the same images upside down?

With OpenCV, I compute the homography between, say, these two images: and Don't worry about the strange white form on the right side, it is due to the smartphone holder I use. The homography, given ...
6k views

Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

Sorry if this is a trivial question but I could not find a suitable answer elsewhere. I recently learned about homography and fundamental matrices in a CV class. I understand how these matrices are ...
1k views

Apply Low Pass (Smoothing) Filter on a Set of Matrices and Reject Outliers

Given a set of a $3$ by $3$ matrices ${H}_{i}$. Each matrix is an Homography matrix. They are used to stabilize Video Stream. Yet some of them are outliers which creates "Jumps" in the "...
3k views

How are the scaling parameters included (extracted from) an essential matrix?

An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as: $$E=K'^TFK$$ where K is the calibration and F ...
2k views

Obtain motion between image features by means of the homography matrix

I have been reading several really good answers about how to obtain camera pose (rotation, translation, etc), such as this one and this one, but I am not sure how this applies to my problem. My ...
311 views

Finding Homography Matrix Using Lines

I have some Points and Lines from original image and the corresponding points and lines from top view image. -> I tried to find homography using points Used OpenCV function findHomography(...
5k views

Ground plane estimation from a single image (was: confusion about homography and calibration camera parameters)

I'm new to this multiple view geometry issues and I'm a little bit lost, and some concept are not clear at all. I have a calibrated camera ( = I have distortion coefficents, field of view, and with ...
1k views

homography matrix problem

i have mini project to do about homography , but i am really a beginner in matlab . i have calculated the homography matrix easily by taking a set pixels from both images but the problem is how to ...
1k views

What methods can be used to compute homography

I am trying to understand panorama stitching. I've come to a conclusion that homography is one of the fundamental parts in the process. Now I am trying to make sense of all the information from ...
36 views

Convert pictures from the same camera with different FOV to pictures with same FOV

I have a camera device that produce two pictures at the time: depth picture with FOV: 87° × 58° RGB picture with FOV: 90 × 65° I expect that they "share" the same objective so their origin ...
20 views

Virtual camera from panorama

I'm trying to virtualize a camera from a panorama. That is, suppose I have a really big picture, for example: a soccer field. Then I want to simulate a camera that focuses on certain regions of the ...
90 views

Measure object planar displacement on slight moving or vibrating plane

I'm working in an application where I'm tracking an object 2d displacement on a given plane and the camera is already calibrated (intrinsic) and the lens distortion has been corrected. In order to ...
25k views

How to apply a 2D -2D homography matrix to an image?

I have a mini project to do about homography, but I am really a beginner in Matlab. I have calculated the homography matrix easily by taking a set pixels from both images but the problem is how to ...
1k views

3D world homography matrix calculation

I have a matrix in (x,y,z) coordinates and also i have a transformed version like (x_new,y_new,z_new). I need to calculate a transformation matrix that can transform (x,y,z) to (x_new,y_new,z_new). ...
18 views

Optimising homography matrix without keypoints

I have two images (frames) that are misaligned. One is reference and for second one I have a homography matrix (which was not calculated by me, I just have it). I warped second frame with homography ...
81 views

Removing feature matched outliers within same image using RANSAC

I'm a student working on a copy move forgery detection algorithm. I have a forged image. By far I have, Found keypoints and descriptors from the image Matched the descriptors using 3 Nearest ...
40 views

Homography valid for patch within the image but not the entire image?

The homography I have is non-degenerate (det!=0), and generated from a valid planar pose. When I use it to warp the four corners of image, it returns something like the following: ...
42 views

Find camera tilt

If I have a camera that captures tilted images what is the way to find the tilt of the camera? Is there a pattern that I can photograph or something similar. I want to reduce the tilt as precisely as ...
70 views

Should we use all $N$ correspondence points to compute Homography or just $4$ points?

Given correspondences of $(x,x')$, we want to find a Homography matrix $H$ that maps $x' = Hx$. If we use 4 corresponding non - collinear points and the matrix $H$ has rank $n-1$, then the homogenous ...
45 views

Finding point height on a cup using OpenCV

Suppose that I want to find the 3D position of a cup with its rotation, with image input like this (this cup can be rotated to point in any direction): Given that I have a bunch of 2D points ...
95 views

Homography for (small baseline) Stereo Image Registration

If the distance between two stereo cameras (baseline) is much smaller than the distance to the geometry, is it possible to align the resulting two stereo images using a homography?
198 views

Homography Matrix Correlations

If the homography matrix of Image 1 to Image 2 is given, and another homography matrix for image 2 to image 3 is given, how do I calculate the homography matrix for image 1 to image 3? PS : I need the ...
43 views

Counting percentage of fouling on a surface

I am completely new to image processing and python. I hope I can find some help here. I am trying out a project on detecting fouling% on a ship hull using raspberry pi. I am trying to learn how this ...