FAQ Database Discussion Community

## How to draw 3D Coordinate Axes with OpenCV for face pose estimation?

opencv,image-processing,3d,computer-vision,camera-calibration
Suppose I have got the face euler angles (pitch, yaw, roll) now. How can draw the 3D Coordinate Axes which show the face pose. Here is an exmaple from here: ...

## Doing camera calibration by having intrinsic matrix and distortion coefficients in OPENCV and in real-time video

I have already used the calibration code provided by opencv to calibrate my camera and everything went ok! I also can undistort any image I want by applying the parameters using a code written in Python. import numpy as np import cv2 # copy parameters to arrays K = np.array([[385.58130632872212,...

## camera extrinsic calibration

computer-vision,camera-calibration,extrinsic-parameters
I have a fisheye camera, which I have already calibrated. I need to calculate the camera pose w.r.t a checkerboard just by using a single image of said checkerboard,the intrinsic parameters, and the size of the squares of the checkerboards. Unfortunately many calibration libraries first calculate the extrinsic parameters from...

## Determine camera pose?

c++,opencv,computer-vision,camera-calibration,perspectivecamera
I am trying to determine camera pose based on fiducial marker found in a scene. Fiducial: http://tinypic.com/view.php?pic=4r6k3q&s=8#.VNLnWTVVK1E Current process: Use SIFT for feature detection Use SIFT for descriptor extraction Use FLANN for matching Find the homography using CV_RANSAC Identify the corners of the fiducial Identify corners of the fiducial in...

## OpencCV error during calibration

c++,opencv,camera-calibration,calibration
This is my calibratio code: void calibrate() { int numBoards = 21; int board_w = 6; int board_h = 9; Size board_sz = Size(board_w, board_h); int board_n = board_w*board_h; vector<vector<Point3f> > object_points; vector<vector<Point2f> > imagePoints1, imagePoints2; vector<Point2f> corners1, corners2; vector<Point3f> obj; for (int j=0; j<board_n; j++) { obj.push_back(Point3f(j/board_w, j%board_w, 0.0f));...

## What is the difference between using an A0 and an A4 camera calibration board ? Is there any ? If yes, what and why?

matlab,opencv,computer-vision,camera-calibration,matlab-cvst
What is the difference between using an A0 and an A4 camera calibration board ? Is there any ? If yes, what and why ? For example, here they use A3 board http://se.mathworks.com/help/vision/ref/estimatecameraparameters.html but here a much larger board : http://se.mathworks.com/help/vision/examples/stereo-calibration-and-scene-reconstruction.html . Why not simply always use a small A4...

## OpenCV Error through calibration tutorial (solvePnPRansac)

python,computer-vision,camera-calibration,opencv3.0,pose-estimation
Can anyone know what is going on with this opencv error ? cv2.error: /home/desktop/OpenCV/opencv/modules/core/src/matrix.cpp:2294: error: (-215) d == 2 && (sizes[0] == 1 || sizes[1] == 1 || sizes[0]*sizes[1] == 0) in function create Line code which raise it is : rvecs, tvecs, inliers = cv2.solvePnPRansac(objp, corners2, cameraMatrix, dist) I...

## Creating stereoParameters class in Matlab: what coordinate system should be used for relative camera rotation parameter?

matlab,computer-vision,coordinate-systems,camera-calibration,matlab-cvst
stereoParameters takes two extrinsic parameters: RotationOfCamera2 and TranslationOfCamera2. The problem is that the documentation is a not very detailed about what RotationOfCamera2 really means, it only says: Rotation of camera 2 relative to camera 1, specified as a 3-by-3 matrix. What is the coordinate system in this case ? A...

## ROS Image subscriber - window popup does not appear

opencv,camera-calibration,ros,subscriber
I am following image subscribe tutorial on official ROS page. when I run my_subscriber no window popup appears. I type - rosrun image_transport_tutorial my_subscriber output is - init done opengl support available And then nothing happens. (even the output "init done" is unexplained because there is not output line in...

## Android Camera2 API Focus Distance Calibration

android,camera-calibration
Currently I have a Nexus 9 that returns a value of "Approximated" when mCameraCharacteristics.get(CameraCharacteristics.LENS_INFO_FOCUS_DISTANCE_CALIBRATION) is called. My question is...what devices are out there that allows for a "Calibrated" device? Or is there a way I can calibrate the camera? An accurate focus distance is very helpful for my application. ...

## Finding 3D coordinate of object

opencv,image-processing,3d,camera-calibration
I try to find 3D coordinate (in world )of abject that I know his coordinate in image .so after some research in internet I succed to find X and Y cordinate. but I can't find Z that is my program in openCV void drawAndCalcul3D(int x,int y,Mat& frame) { cv::Mat uvPoint...

## disparity map's color is reversed

c++,opencv,camera-calibration,disparity-mapping
the result of my disparity map is good. as I know , close items should be light and far items are dark . The opposite happens with me. this is my code: CvStereoBMState *BMState = cvCreateStereoBMState(); assert(BMState != 0); BMState->preFilterSize=31/*41*/; BMState->preFilterCap=41/*31*/; BMState->SADWindowSize=31/*41*/; BMState->minDisparity=-0/*-64*/; BMState->numberOfDisparities=112/*128*/; try { while(true) { if(true) {...

## camera frame world coordinates relative to fiducial

opencv,computer-vision,camera-calibration,perspectivecamera
I am trying to determine camera position in world coordinates, relative to a fiducial position based on fiducial marker found in a scene. My methodology for determining the viewMatrix is described here: Determine camera pose? I have the rotation and translation, [R|t], from the trained marker to the scene image....

## Project image points to object points with opencv 3.0.0 beta

opencv,camera-calibration,fisheye,opencv3.0
I use opencv 3.0.0 beta. I calibrated my camera and I would like project image points (2D) to points in 3D. I saw the function :void fisheye::projectPoints(InputArray objectPoints, OutputArray imagePoints, InputArray rvec, InputArray tvec, InputArray K, InputArray D, double alpha=0, OutputArray jacobian=noArray()) but I would like the opposite projection. I...

## Image correction in visual odometry

matlab,computer-vision,camera-calibration,matlab-cvst
I am trying to implement visual odometry algorithm via matlab. According to step 2 in http://en.wikipedia.org/wiki/Visual_odometry. I need to do image correction before feature detection, matching and motion estimation. I think I need to undistort image like the function (here) in matlab. Can I use the original intrinsic and extrinsic...