Calibration Pattern As we said earlier we are going to need some sort of pattern that the program can recognize in order to make the calibration work. The pattern that we are going to use is a chessboard image. The reason why we use this image is because there are some OpenCV functions that can recognize this pattern and draw a scheme which highlights the intersections between each block. To make the calibration work you need to print the chessboard image and show it to the cam; it is important to maintain the sheet still, better if stick to a surface.

The latter is described in opencv1x.pdf. OpenCV has a modular structure, which means that the package includes several shared or static libraries. The following modules are available. Use OpenCL in Android camera preview based CV application. Using OpenCV Java with Eclipse. OpenCV - Bug # 2831: FindChessboardCorners cannot detect chessboard on very large resoluction images Status: Done Priority: Normal Author: Tom Guo Category. A black and white chessboard. In this section we consider the OpenCV chessboard pattern that has a size of 9 by 6. Chess5x7x0.03.pdf; chess7x9x0.025.pdf.

In order to make a good calibration, we need to have about 20 samples of the pattern taken from different angles and distances. • image Source chessboard view.

It must be an 8-bit grayscale or color image. • patternSize Number of inner corners per a chessboard row and column • corners Output array of detected corners.

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• flags Various operation flags that can be zero or a combination of the following values: • CV_CALIB_CB_ADAPTIVE_THRESH Use adaptive thresholding to convert the image to black and white, rather than a fixed threshold level (computed from the average image brightness). • CV_CALIB_CB_NORMALIZE_IMAGE Normalize the image gamma with “equalizeHist” before applying fixed or adaptive thresholding. • CV_CALIB_CB_FILTER_QUADS Use additional criteria (like contour area, perimeter, square-like shape) to filter out false quads extracted at the contour retrieval stage. • CALIB_CB_FAST_CHECK Run a fast check on the image that looks for chessboard corners, and shortcut the call if none is found. This can drastically speed up the call in the degenerate condition when no chessboard is observed.

List rvecs = new ArrayList (); List tvecs = new ArrayList (); intrinsic. Put ( 0, 0, 1 ); intrinsic. Put ( 1, 1, 1 ); Calib3d. CalibrateCamera ( objectPoints, imagePoints, savedImage. Size (), intrinsic, distCoeffs, rvecs, tvecs ); The calibrateCamera function estimates the intrinsic camera parameters and extrinsic parameters for each of the views.

The algorithm is based on [Zhang2000] and [BouguetMCT]. The coordinates of 3D object points and their corresponding 2D projections in each view must be specified. Its parameters are.

• objectPoints In the new interface it is a vector of vectors of calibration pattern points in the calibration pattern coordinate space. The outer vector contains as many elements as the number of the pattern views. The points are 3D, but since they are in a pattern coordinate system, then, if the rig is planar, it may make sense to put the model to a XY coordinate plane so that Z-coordinate of each input object point is 0. • imagePoints It is a vector of vectors of the projections of calibration pattern points. • imageSize Size of the image used only to initialize the intrinsic camera matrix. • cameraMatrix Output 3x3 floating-point camera matrix A = fx 0 cx 0 fy cy 0 0 1 . If CV_CALIB_USE_INTRINSIC_GUESS and/or CV_CALIB_FIX_ASPECT_RATIO are specified, some or all of fx, fy, cx, cy must be initialized before calling the function.