A homography is an invertible transformation from the real projective plane to the projective plane that maps straight lines to straight lines. This tag should be used for questions related to homography transformations (camera rotation, translation,...) in the computer vision field.
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how to generateRandomTransform with OpenCV
I tried to generate Random Homography Matrix that could be used to transform planar object image. It seems that opencv has a class "patchgenerator". But I can't find detailed information of this ...
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Find projection matrix
at first I want to apologize for my bad English.
I am really new in OpenCV and in virtual reality. I tried to find out the theory of image processing, but some points are missing there for me. I ...
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Croping out Extreme Distortion from Homography
I have a picture of a checkerboard taken from an arbitrary camera angle. I find the two vanishing points corresponding to the two sets of lines that form the checkerboard grid. From these two ...
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OpenCV 2.4.3 - warpPerspective with reversed homography on a cropped image
When finding a reference image in a scene using SURF, I would like to crop the found object in the scene, and "straighten" it back using warpPerspective and the reversed homography matrix.
Meaning, ...
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51 views
OpenCV: use homography for different image sizes
I calculate the homography matrix of an image using OpenCV's findHomography and then I warp the image using warpPerspective function. Now I want to use the same homography matrix for a scaled version ...
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2answers
141 views
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; ...
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93 views
How to warp a jpg image using homography
Hi I am working on creating a panorama with two images.
Here is the link that I am using as a guideline to do this.
...
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58 views
Difference between Fundamental , Essential and Homography matrices
I have two images which are taken from different positions. The 2nd camera is located to the right,up and backward with respect to 1st camera. So I think there is a perpective transformation between ...
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153 views
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 ...
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193 views
OpenCV c++ findHomography mask values meaning
I am using the function findHomography of OpenCV with the RANSAC method in order to find the homography that relates two images linked with a set of keypoints. Main issue is that I haven’t been able ...
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1answer
140 views
ORB Feature Detector
I'm working on a Marker less augmented reality project with Open CV. Currently i'm using ORB to detector features and augment 3D Objects. So far the models are augmented well but the augmentation is ...
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1answer
407 views
how to get Homography matrix using OpenCV (Stitching 2 images)
I'm working on OpenCV in visual studio 2012 , i tried to get Homography matrix to Stitch 2 images in opencv so really i don't know the steps to follow to do'it :
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Warping GUI elements in Unity's OnGUI
I am using Unity3D, and I have a function which is being called inside of OnGUI to lay out the various gui components of my application. Ordinarily, the labels and buttons are all inside of a certain ...
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191 views
How to get rotation, translation, shear from a 3x3 Homography matrix in c#
I calculated the 3x3 homography matrix and I need to get rotation, translation, shear and scale to use them as parameters in the windows8 media element attributes ?!
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257 views
Finding Homography using three correspondent (P3P solution)
I want to compute 6DOF rigid transform given 3 correspondents and camera Intrinsic parameters.
I am following a tutorial here
Let me formulate my problem:
camera matrix is K=[416 0 240 ...
...
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1answer
138 views
Image Rectification for Shake Correction on OpenCV
I've 2 pictures of the same scene from an uncalibrated camera. The pics are from a slightly different angle and scale(zoom) and I'd like to superpose them, rejecting any kind of shake. In other words, ...
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347 views
How to check if obtained homography matrix is good?
This question was already asked, but I still don't get it. I obtain a homography matrix by calling cv::findHomography from a set of points. I need to check whether it's relevant or not. The proposed ...
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1answer
180 views
Image 3D rotation OpenCV
I need to perform a 3D rotation of a 2D image on x and y axis.
I read that i have to use the Homographic matrix on OpenCV , but i don't know how to set the matrix to perform a common rotation angle. ...
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85 views
How to sample image given the Homography Matrix
I have applied some keypoint extraction to two images and worked out the homography H matrix between two objects of interest. Now, when I do some inverse mapping from a new image with warpPerspective ...
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1answer
179 views
Multiple Image stitching - Adding a third image
I am trying to stitch a third image after stitching two images together but it doesn't seem to work.
To elaborate, I successfully stitched two images together using the code given in the opencv ...
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2answers
596 views
How to estimate 2D affine transform by RANSAC in OpenCV?
I'm trying to search a specific object in input images by matching SIFT descriptors and finding the transformation matrix by RANSAC. The object can only be modified in scene by similarity transform in ...
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3answers
346 views
Transform point position in trapezoid to rectangle position
I am trying to find out how I can transform a coordinate Pxy within the green trapezoid below into the equivalent coordinate on the real ground plane.
I have the exact measures of the room, meaning I ...
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1answer
275 views
Confusion about methods of pose estimation
I'm trying to do pose estimation (actually [Edit: 3DOF] rotation is all I need) from a planar marker with 4 corners = 4 coplanar points.
Up until today I was under the impression from everything I ...
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1answer
512 views
Calculate camera world position with OpenCV Python
I want to calculate my camera's position in world coordinates. This should be fairly easy, but I don't get the results I expect. I believe I've read everything on this topic, but my code isn't ...
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2answers
518 views
OpenCV CV findHomography assertion error - counter => 4
I'm currently finishing my evaluation-tool for interest point detectors. In the last steps I found a confusing error.
Mat findHomography(InputArray srcPoints, InputArray dstPoints, int method=0, ...
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1answer
320 views
Homography estimation -> result an affine matrix?
I am developing a pose estimation system from a planar marker (using Matlab).
In order to do that, I detect a rectangle in an image captured with a webcam, get the coordinates of the 4 corner points ...
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168 views
calculating objects height from video by knowing the homography in OpenCV
I'm trying to measure the heights of the objects detected in my tracking application I'm developing using OpenCV and Python. I've calculated the homography matrix so I know every object's location in ...
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143 views
Bad image stabilization result opencv
I’m working on video stabilization using opencv under C++. I got correct matched features from each couple of frames using LK optical flow : cvCalcOpticalFlowPyrLK function. Actually the camera is ...
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267 views
Homography computation using Levenberg Marquardt algorithm
The findHomography() function in OpenCV finds a perspective transformation between two planes.The computed homography matrix is refined further (using inliers only in case of a robust method) with the ...
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358 views
How Can I Perform a Perspective Transform Using a Homography Matrix (3x3) in JavaCV?
I have been trying for some time now to take an image of a pool table from an arbitrary angle, locate four coordinate pairs (x,y) of the corners, and rotate/warp the image such that the resulting ...
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1answer
102 views
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, height);
...
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1answer
390 views
Finding the camera orientation from a homography, opencv
If I have a camera which is already calibrated, so that I already know distortion coefficients, and the camera matrix. And that I have a set of points that all are in a plane, and I know the realworld ...
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141 views
Using homography for a virtual monitor [closed]
I'm currently working on a project where I need to create a virtual screen for feedback during a game
My program draws an image at a tracked position. What I wan't it to do is to have this image ...
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429 views
HOW TO use Homography to transform pictures in OpenCV?
I've two pictures (A and B) slightly distorted one from the other, where there are translation, rotation and scale differences between them (for example, these pictures:)
Ssoooooooo what I need ...
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261 views
OpenCV Stitching Module: BestOf2NearestMatcher - Unknown translations
I am trying to use OpenCV's BestOf2NearestMatcher class found within their stitching module. From my understanding it takes feature points from 2 images, then calculates the homography between the 2 ...
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205 views
Define detected Object width with SURF in OpenCV
i am working under a robotic project. Exactly with object detect with SURF on opencv. I found many codes on the net of objects detection. What i didn't found exactly is the width of the object in the ...
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2answers
344 views
How can I use Homography?
I am developing a program where I receive 2 pictures of the same scene, but one of them has a distortion:
Mat img_1 = imread(argv[1], 0); // nORMAL pICTURE
Mat img_2 = imread(argv[2], 0); // ...
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247 views
cv::findHomography gioving error c2665
I looked at this code which gives
http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html
//-- Localize the object
std::vector<Point2f> obj;
...
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3answers
713 views
How to detect a quadrilateral shape in an image in Java?
I want to detect a quadrilateral shape in an image in Java. I can use the HoughLinesP method in OpenCV (using javaCV for opencv java binding) to detect line segments. But I can't figure out how to ...
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440 views
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 ...
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1answer
255 views
Find Homography for three pairs of 2D/2D correspondents
I have a three feature points in an image and their matches in another image.
My question is how to find a homography that relates these matches to each other?
I know I should solve P3P problem.But I ...
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1answer
470 views
Planar object Homography calculation and Pose Estimation
I'm trying to implement my own Homography and Pose estimation in OpenCV. Suppose I have a square image as a model which I want to locate in input frame from camera.
My question is about how to prepare ...
2
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1answer
139 views
Camera homography
I am learning camera matrix stuff. I already known that I can get the homography of the camera (3*3 matrix) by using four points in a plane in object space. I want to know if we can get the homagraphy ...
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2answers
428 views
cvPerspectiveTransform: What am I supposed to provide?
I'm trying to use cvPerspectiveTransform to transform four 2D points. I got the transformation matrix (3x3) already through cvFindHomography. I can't figure out what kind of structure to provide to ...
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2answers
380 views
Fast algorithm for detecting an object in an image
I'm working on a small program for optical mark recognition.
The processing of the scanned form consists of two steps:
1) Find the form in the scanned image, descew and crop borders.
2) With this ...
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1answer
488 views
How do I use a Homography Matrix properly?
So I have an image, and a panoramic image. Pixels from image1 are mapped to the panorama using a Homography matrix (is that correct?). I have the Homography Matrix H.
So, for each pixel in panorama, ...
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228 views
Open CV Surf And FindExtrinsicCameraParams2
Is it possible to use FindExtrinsicCameraParams2 to get the pose matrix instead of using homography decomposition with SURF feature detection ?
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OpenCV uncalibrated camera rectification for 3D reconstruction
I'm running OpenCV 2.4.2.
My project consists into a 3D face identification.
I'm trying to create a 3D model from a pairs of images taken by an uncalibrated camera.
My goal is to get some 3D ...
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126 views
how to find rectifying matrix using OpenCV
I'm not an expert in this area yet. I have a weak understanding in computer vision so it's hard to grasp things from the document. I have a rather urgent job to do which is to find two matrices which ...
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198 views
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 secene and extract features again. I match the points and extract the ...
