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Questions tagged [homography]

A homography is an invertible mapping from points in the the real projective plane to points in the real projective plane that maps straight lines to straight lines. This tag should be used for questions related to homography transformations (pure camera rotation, planar scenes, ...) in the computer vision field.

A homography is an invertible mapping h from the real projective plane to itself such that three points x1, x2and x3 lie on the same line if and only if h(x1), h(x2) and h(x3) do. Each homography is represented in homogeneous coordinates by a non-singular 3x3 matrix H such that for any point in the real projective plane represented by a vector x it is true that h(x) = Hx.

enter image description here

When applied to every pixel the new image is a warped version of the original image.

Source: wikipedia

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Multiple camera image stitching

I've been running a project of stitching images from multiple cameras, but I think I've got a bottleneck...I have some questions about this issue. I wanna try to mount them on a vehicle in the future and that means the relative positions and…
SilentButDeadly JC
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Can I reuse Homography matrix calculated from 2 different images of same scene taken by 2 different cameras?

I'm trying to learn OpenCV. I've a question regarding homography and epipolar geometry. Suppose I've calculated homography using cvFindHomography() function using two static images' matched feature points taken with two cameras from two different…
mvr950
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How to find 3d Projection Matrix in Surf Detection

I am new to OpenCV. I have got the Surf Detection sample working. Now I want to place a 3d model on the detected image. How can I find the 3d Projection matrix?
Sumeet Jindal
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4-point transform images

I need to transform bitmap images with their 4 corner points moved from one location to another. Any code that can run on Windows, C#/VB.NET preferably, even help how to use scriptable programs like Paint.NET or Photoshop would be accepted. The Java…
Robin Rodricks
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How to augment cube onto a specific position using 3x3 homography

I am able to track 4 coordinates over different images of the same scene by calculating a 3x3 homography between them. Doing this I can overlay other 2D images onto these coordinates. I am wondering if I could use this homography to augment a cube…
John
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How do I use the relationships between Flann matches to determine a sensible homography?

I have a panorama image, and a smaller image of buildings seen within that panorama image. What I want to do is recognise if the buildings in that smaller image are in that panorama image, and how the 2 images line up. For this first example, I'm…
Andrew
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Can I simply add affine or perspective (homography) matrices of transformation?

As known, in OpenCV I can get affine or perspective transformation between 2 images: M - affine transformation - by using estimateRigidTransform() H - perspective (homography) transformation - by using FeatureDetector (SIFT, SURF, BRISK, FREAK,…
Alex
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Using estimateRigidTransform instead of findHomography

The example in the link below is using findHomography to get the transformation between two sets of points. I want to limit the degrees of freedom used in the transformation so want to replace findHomography with…
Tom smith
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2D-3D homography matrix estimation

I am working with my Kinect on some 2D 3D image processing. Here is my problem: I have points in 3D (x,y,z) which lie on a plane. I also know the coordinates of the points on the RGB image (x,y). Now I want to estimate a 2D-3D homography matrix to…
user2576458
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Projecting a 2D point from a marker to the image with computed homography

I have a planar marker where I have run the SIFT algorithm to extract features. Then I run a detector to find this marker in the scene and extract features again. I match the points and extract the homography from the matched pairs with OpenCV using…
Mar de Romos
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calculating the destination points for OpenCV's findHomography

EDIT: I've now found this similar question with a very detailed answer: proportions of a perspective-deformed rectangle I'm using OpenCV's findHomography() and warpPerspective() methods to "de skew" a photograph of a sheet of paper. I have this…
TomSwift
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Calculating homography matrix using arbitrary known geometrical relations

I am using OpenCV for an optical measurement system. I need to carry out a perspective transformation between two images, captured by a digital camera. In the field of view of the camera I placed a set of markers (which lie in a common plane), which…
Marcin
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finding the mapping between video point and real world point

I am doing car tracking on a video. I am trying to determine how many meters it traveled. I randomly pulled 7 points from a video frame. I made point1 as my origin Then on the corresponding Google Maps perspective, I calcculated the distances of the…
Snake
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Opencv homography to find global xy coordinates from pixel xy coordinates

I am trying to find the transformation matrix H so that i can multiply the (x,y) pixel coordinates and get the (x,y) real world coordinates. Here is my code: import cv2 import numpy as np from numpy.linalg import inv if __name__ == '__main__'…
Vivek Annem
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Error when running solvePnP in OpenCV Python

I am trying to make an augmented reality program in OpenCV. But I seem to always get an error when I call solvePnP. What I am trying to do is make an augmented reality program in OpenCV by taking homography points of a selected cropped image to the…
user3377126
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