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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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Homography array transformation

I am working on a homography method to copy and expand the relevant points from a rectangle area of depthImg array to a new array, but the bottomright points do not change the homographyImg array. Any ideas, suggestions appreciated. Thanks and happy…
kockaART
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How can I find the aspect ratios of 2 "rectangles" on the same plane in a 3d image?

Based on this paper On page 4 the authors indicate they will rectify these 2 quadrilaterals by computing a homography, using TWO DEFINING LINES to determine the aspect ratio. I understand the transform using the homography should be quite simple if…
user3003140
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Homography Error

first I would like to state that I'm a very noob at c++. I am using to compile and run code from Features2D + Homography to find a known object tutorial, but I think I'm having trouble in linking correctly the libraries needed. I am getting…
Livio Pires
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OpenCV: Recording a Warped Video

I am making a small application in C++ (using OpenCV) that records a video and then lets you warp it by rotating your view in x,y,z. Right now I am just starting to test the rotation by making it rotate a small angle every iteration. Although the…
nrxus
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Why is the planar homography not completely sufficient to map any arbitrary scene image to another viewpoint

I just have a very basic question for Computer vision homography. Why is the planar homography not completely sufficient to map any arbitrary scene image to another viewpoint? The points must be on one plane. So the image points behind 2 cameras…
Keqin Dou
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Once I get the Homography Matrix from OpenCV and Visual Studio 2010, How I use it?

I have calculated the Homography Matrix using OpenCV and Visual Studio. I have used the basic example of this topic. How should I apply that matrix?...
mantoniogr
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Homography Matrix for Image Stitching in MATLAB

ive been trying to compute the homography matrix in matlab by using manually selected corresponding points from 2 images. here is my code so far: spoints = [330.756756756757,923.310810810811; %points from source image …
Khyzer Irfan IV
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Image Registration by Manual marking of corresponding points using OpenCV

I have a processed binary image of dimension 300x300. This processed image contains few object(person or vehicle). I also have another RGB image of the same scene of dimensiion 640x480. It is taken from a different position note : both cameras…
Karthik Murugan
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Opengl 2D drawing not parallel to screen

I think the 2D plane I draw on is not parallel to the screen. First, in my resize window function I put: static void Resize(int w, int h) { width = w; height = h; glViewport(0, 0, width,…
Min Lin
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Imaging stitching with openCV - final stage difficulty

I'm using OpenCV 2.4 to convert a video into a long (narrow) mosaic. This is my first time using OpenCV, but so far I've managed the following with some success: Get frames from video. Get keypoint descriptors using SIFT. Sort out the outliers…
user943354
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Homography for Image Rectification

We can do image rectification given stereo images. For a single image we can find the two vanishing points and then the vanishing line. Using this vanishing line we can do projective rectification. But what constraints are required for affine…
Harshit Agrawal
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Use homography to warp four corners of image and it returns invalid quadrangle

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: 1 0 3 2 instead of something like 0 1 3 2 where 0 represents…
Philip Zaro
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Aligning images using openCV

I have a collection of roughly 250 images. All of them were scanned from a book, hence they are all shifted or rotated a little with regards to each other. Now I would like to do some data extraction on these images, but in order to do this…
Frederik Vanclooster
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OpenCV perspectiveTransform broken function

Im trying to use perspectiveTransform but I keep getting error. I tried to follow the solution from this thread http://answers.opencv.org/question/18252/opencv-assertion-failed-for-perspective-transform/ _players[i].getCoordinates() is of type…
RuiQi
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How to find point position relation between two images using homography?

I'm working on vision project with OPENCV : how to find point x position in an image B knowing it's position in image A? and that the two projections are of the same plane ( the floor). thanks for your answers.
ELYAS
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