I’m trying to implement a stereo camera calibration app using emgu cv.
My problem is when I try to use CvInvoke.cvRemap to undistort an image the function just hangs. No errors or crashes, it just hangs and I’ve left it for 2 hours in case it was just being slow. Here’s what I’m doing:
- Capturing 10 pairs of Chessboard samples (left and right), making sure FindChessboardCorners works on each. I’m not doing anything special to sync the cameras just capturing them at the same time.
- Generate set of object points based off the chessboard used.
- Doing a separate CalibrateCamera on the left and right images of each sample using the object points from 2 and the image points from 1.
- Doing a StereoCalibrate using the IntrinsicCameraParameters generated by CalibrateCamera in 3, the object points in 2, and the image points captured from the chessboards in 1.
- Doing a StereoRectify using the IntrinsicCameraParameters from 3/4.
- Generating mapx and mapy for both left and right from cvInitUndistortRectifyMap using output from 5.
- Attempting to cvRemap using mapx and mapy from 6 and fresh images captured from the cameras.
NEXT: Use StereoBM.FindStereoCorrespondence and PointCollection.ReprojectImageTo3D to generate a point cloud from my hopefully calibrated stereo data.
So when I get to 7 cvRemap just hangs. I’ve gotton cvRemap to work capturing from a single camera though so I know the function is working to some degree with my setup.
I’ve written a class to manage multiple cameras:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
using Emgu.CV;
using Emgu.CV.UI;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;
using Emgu.CV.VideoSurveillance;
namespace Capture2Cams
{
class camData
{
public Capture capture;
public Image<Bgr, Byte> lastFrame;
public Image<Gray, Byte> lastFrameGray;
public bool lastChessboardFound;
public PointF[] lastChessboardCorners;
public Image<Gray, Byte>[] samplesGray;
public PointF[][] samplesChessboardCorners;
public Size cbDimensions;
public Size imageDimensions;
public int cursampleIndex = 0;
public ImageList sampleIcons;
private Image<Gray, Byte> _chessBoardDisplay;
private int _iconWidth = 160;
private int _icnonHeight = 90;
private int _numSamples = 0;
public int numSamples()
{
return _numSamples;
}
public void numSamples(int val)
{
_numSamples = val;
this.samplesGray = new Image<Gray, Byte>[val];
this.samplesChessboardCorners = new PointF[val][];
this.sampleIcons.ImageSize = new Size(_iconWidth, _icnonHeight);
Bitmap tmp = new Bitmap(_iconWidth, _icnonHeight);
this.sampleIcons.Images.Clear();
for (int c = 0; c < _numSamples; c++) this.sampleIcons.Images.Add(tmp);
}
public camData(int camIndex, int capWidth, int capHeight, int pcbWidth, int pcbHeight, int pNumSamples)
{
this.sampleIcons = new ImageList();
try
{
this.capture = new Capture(camIndex);
this.capture.SetCaptureProperty(CAP_PROP.CV_CAP_PROP_FRAME_WIDTH, capWidth);
this.capture.SetCaptureProperty(CAP_PROP.CV_CAP_PROP_FRAME_HEIGHT, capHeight);
}
catch (Exception e)
{
MessageBox.Show(e.Message);
return;
}
this.imageDimensions = new Size(capWidth, capHeight);
this.cbDimensions = new Size(pcbWidth, pcbHeight);
this.numSamples(pNumSamples);
}
public Image<Gray, Byte> captureFrame()
{
this.lastFrame = this.capture.QueryFrame();
this.lastFrameGray = this.lastFrame.Convert<Gray, Byte>();
return this.lastFrameGray;
}
public int captureSample()
{
this.detectChessboard(true); // detectChessboard calls -> captureFrame
if (lastChessboardFound)
{
this.samplesGray[cursampleIndex] = this.lastFrameGray;
this.samplesChessboardCorners[cursampleIndex] = this.lastChessboardCorners;
this.sampleIcons.Images[this.cursampleIndex] = this.lastFrameGray.ToBitmap(_iconWidth, _icnonHeight);
this.cursampleIndex++;
if (this.cursampleIndex >= _numSamples) this.cursampleIndex = 0;
}
return cursampleIndex;
}
public void clearSamples()
{
this.cursampleIndex = 0;
this.numSamples(_numSamples);
}
public Image<Gray, Byte> detectChessboard(bool pDoCapture)
{
if (pDoCapture) this.captureFrame();
this.lastChessboardFound = CameraCalibration.FindChessboardCorners(this.lastFrameGray, this.cbDimensions, CALIB_CB_TYPE.ADAPTIVE_THRESH | CALIB_CB_TYPE.FILTER_QUADS, out this.lastChessboardCorners);
_chessBoardDisplay = this.lastFrameGray.Clone();
CameraCalibration.DrawChessboardCorners(this._chessBoardDisplay, this.cbDimensions, this.lastChessboardCorners, this.lastChessboardFound);
return this._chessBoardDisplay;
}
public void saveSampleImages(string pPath, string pID)
{
for(int ic = 0; ic < this._numSamples; ic++)
{
this.samplesGray[ic].Save(pPath + pID + ic.ToString() + ".bmp");
}
}
public void loadSampleImages(string pPath, string pID)
{
clearSamples();
for (int ic = 0; ic < this._numSamples; ic++)
{
this.lastFrameGray = new Image<Gray, byte>(new Bitmap(pPath + pID + ic.ToString() + ".bmp"));
this.detectChessboard(false);
this.samplesChessboardCorners[ic] = this.lastChessboardCorners;
this.sampleIcons.Images[ic] = this.lastFrameGray.ToBitmap(_iconWidth, _icnonHeight);
this.samplesGray[ic] = this.lastFrameGray;
}
}
}
}
And here’s my form code with the rest of the calibration logic:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using Emgu.CV.Util;
using Emgu.CV;
using Emgu.CV.UI;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;
using Emgu.CV.VideoSurveillance;
namespace Capture2Cams
{
public partial class CaptureForm : Form
{
private static camData camLeft;
private static camData camRight;
private int _numSamples = 10; // Number of calibration samples
private int _imageWidth = 1280; // web cam resolution
private int _imageHeight = 720; // web cam resolution
private int _cbWidth = 9; // chessboard corner count
private int _cbHeight = 5; // chessboard corner count
// TODO: Test post calibration values, these will need to be loaded and saved
private static Matrix<double> _foundamentalMatrix;
private static Matrix<double> _essentialMatrix;
private static IntrinsicCameraParameters _inPramsLeft;
private static IntrinsicCameraParameters _inPramsRight;
private static ExtrinsicCameraParameters _outExtParamsStereo;
private Matrix<float> _mapxLeft;
private Matrix<float> _mapyLeft;
private Matrix<float> _mapxRight;
private Matrix<float> _mapyRight;
public CaptureForm()
{
InitializeComponent();
Run();
}
void Run()
{
camLeft = new camData(0, _imageWidth, _imageHeight, _cbWidth, _cbHeight, _numSamples);
camRight = new camData(1, _imageWidth, _imageHeight, _cbWidth, _cbHeight, _numSamples);
this.listViewLeft.LargeImageList = camLeft.sampleIcons;
for (int c = 0; c < _numSamples; c++)
{
ListViewItem curItem = new ListViewItem();
curItem.ImageIndex = c;
curItem.Text = "Sample" + c.ToString();
this.listViewLeft.Items.Add(curItem);
}
this.listViewRight.LargeImageList = camRight.sampleIcons;
for (int c = 0; c < _numSamples; c++)
{
ListViewItem curItem = new ListViewItem();
curItem.ImageIndex = c;
curItem.Text = "Sample" + c.ToString();
this.listViewRight.Items.Add(curItem);
}
Application.Idle += ProcessFrame;
}
void ProcessFrame(object sender, EventArgs e)
{
if (!checkBoxRectify.Checked)
{
if (this.checkBoxCapCB.Checked)
{
imageBoxLeft.Image = camLeft.detectChessboard(true);
imageBoxRight.Image = camRight.detectChessboard(true);
}
else
{
imageBoxLeft.Image = camLeft.captureFrame();
imageBoxRight.Image = camRight.captureFrame();
}
}
else
{
camLeft.captureFrame();
camRight.captureFrame();
Image<Gray, byte> imgLeft = camLeft.lastFrameGray.Clone();
Image<Gray, byte> imgRight = camRight.lastFrameGray.Clone();
CvInvoke.cvRemap(camLeft.lastFrameGray.Ptr, imgLeft.Ptr, _mapxLeft.Ptr, _mapyLeft.Ptr, (int)INTER.CV_INTER_LINEAR | (int)WARP.CV_WARP_FILL_OUTLIERS, new MCvScalar(0));
CvInvoke.cvRemap(camRight.lastFrameGray.Ptr, imgRight.Ptr, _mapxRight.Ptr, _mapyRight.Ptr, (int)INTER.CV_INTER_LINEAR | (int)WARP.CV_WARP_FILL_OUTLIERS, new MCvScalar(0));
imageBoxLeft.Image = imgLeft;
imageBoxRight.Image = imgRight;
}
//checkBoxRectify
}
private void buttonCaptureSample_Click(object sender, EventArgs e)
{
camLeft.captureSample();
camRight.captureSample();
this.listViewLeft.Refresh();
this.listViewRight.Refresh();
}
private void buttonStereoCalibrate_Click(object sender, EventArgs e)
{
// We should have most of the data needed from the sampling with the camData objects
int numCorners = _cbWidth * _cbHeight;
// Calc intrisitcs / camera
_inPramsLeft = new IntrinsicCameraParameters();
_inPramsRight = new IntrinsicCameraParameters();
ExtrinsicCameraParameters[] outExtParamsLeft;
ExtrinsicCameraParameters[] outExtParamsRight;
//Matrix<double> foundamentalMatrix;
//Matrix<double> essentialMatrix;
outExtParamsLeft = new ExtrinsicCameraParameters[_numSamples];
outExtParamsRight = new ExtrinsicCameraParameters[_numSamples];
_outExtParamsStereo = new ExtrinsicCameraParameters();
// Building object points
// These are the points on the cessboard in local 3d coordinates
// Requires one set per sample, if the same calibration object (chessboard) is used for each sample then just use the same set of points for each sample
// Also setting sub pixel analasys on samples
MCvPoint3D32f[][] objectPoints = new MCvPoint3D32f[_numSamples][];
for (int sc = 0; sc < _numSamples; sc++) // Samples count
{
// indivual cam setup
outExtParamsLeft[sc] = new ExtrinsicCameraParameters();
outExtParamsRight[sc] = new ExtrinsicCameraParameters();
// Sub pixel analasys
camLeft.samplesGray[sc].FindCornerSubPix(new PointF[][] { camLeft.samplesChessboardCorners[sc] }, new Size(10, 10), new Size(-1, -1), new MCvTermCriteria(300, 0.01));
camRight.samplesGray[sc].FindCornerSubPix(new PointF[][] { camRight.samplesChessboardCorners[sc] }, new Size(10, 10), new Size(-1, -1), new MCvTermCriteria(300, 0.01));
// Object points
objectPoints[sc] = new MCvPoint3D32f[numCorners];
for (int cc = 0; cc < numCorners; cc++) // chessboard corners count
{
objectPoints[sc][cc].x = cc / _cbWidth;
objectPoints[sc][cc].y = cc % _cbWidth;
objectPoints[sc][cc].z = 0.0f;
}
}
Size imageSize = new Size(_imageWidth, _imageHeight);
// Indivual cam camibration
CameraCalibration.CalibrateCamera(objectPoints, camLeft.samplesChessboardCorners, imageSize, _inPramsLeft, CALIB_TYPE.DEFAULT, out outExtParamsLeft);
CameraCalibration.CalibrateCamera(objectPoints, camRight.samplesChessboardCorners, imageSize, _inPramsRight, CALIB_TYPE.DEFAULT, out outExtParamsRight);
// Stereo Cam calibration
CameraCalibration.StereoCalibrate(
objectPoints,
camLeft.samplesChessboardCorners,
camRight.samplesChessboardCorners,
_inPramsLeft,
_inPramsRight,
imageSize,
CALIB_TYPE.CV_CALIB_FIX_ASPECT_RATIO | CALIB_TYPE.CV_CALIB_ZERO_TANGENT_DIST | CALIB_TYPE.CV_CALIB_FIX_FOCAL_LENGTH,
new MCvTermCriteria(100, 0.001),
out _outExtParamsStereo,
out _foundamentalMatrix,
out _essentialMatrix
);
PrintIntrinsic(_inPramsLeft);
PrintIntrinsic(_inPramsRight);
}
private void listViewLeft_ItemSelectionChanged(object sender, ListViewItemSelectionChangedEventArgs e)
{
}
private void listViewRight_ItemSelectionChanged(object sender, ListViewItemSelectionChangedEventArgs e)
{
}
private void buttonSaveSamples_Click(object sender, EventArgs e)
{
camLeft.saveSampleImages(textBoxSavePath.Text, "left");
camRight.saveSampleImages(textBoxSavePath.Text, "right");
}
private void buttonLoadSamples_Click(object sender, EventArgs e)
{
camLeft.loadSampleImages(textBoxSavePath.Text, "left");
camRight.loadSampleImages(textBoxSavePath.Text, "right");
this.listViewLeft.Refresh();
this.listViewRight.Refresh();
}
private void buttonCapture_Click(object sender, EventArgs e)
{
}
private void buttonCaptureCurframe_Click(object sender, EventArgs e)
{
camLeft.captureFrame();
camRight.captureFrame();
camLeft.lastFrame.Save(textBoxSavePath.Text + "frameLeft" + ".bmp");
camLeft.lastFrameGray.Save(textBoxSavePath.Text + "frameLeftGray" + ".bmp");
camRight.lastFrame.Save(textBoxSavePath.Text + "frameRight" + ".bmp");
camRight.lastFrameGray.Save(textBoxSavePath.Text + "frameRightGray" + ".bmp");
}
public void StereoRectify(
IntrinsicCameraParameters intrinsicParam1,
IntrinsicCameraParameters intrinsicParam2,
Size imageSize,
ExtrinsicCameraParameters extrinsicParams,
out Matrix<double> R1,
out Matrix<double> R2,
out Matrix<double> P1,
out Matrix<double> P2,
out Matrix<double> Q,
STEREO_RECTIFY_TYPE flags,
double alpha,
Size newImageSize,
ref Rectangle validPixROI1,
ref Rectangle validPixROI2
)
{
R1 = new Matrix<double>(3, 3);
R2 = new Matrix<double>(3, 3);
P1 = new Matrix<double>(3, 4);
P2 = new Matrix<double>(3, 4);
Q = new Matrix<double>(4, 4);
CvInvoke.cvStereoRectify(
_inPramsLeft.IntrinsicMatrix.Ptr,
_inPramsRight.IntrinsicMatrix.Ptr,
_inPramsLeft.DistortionCoeffs.Ptr,
_inPramsRight.DistortionCoeffs.Ptr,
imageSize,
extrinsicParams.RotationVector.Ptr,
extrinsicParams.TranslationVector.Ptr,
R1.Ptr,
R2.Ptr,
P1.Ptr,
P2.Ptr,
Q.Ptr,
STEREO_RECTIFY_TYPE.DEFAULT,
alpha,
newImageSize,
ref validPixROI1,
ref validPixROI1);
}
public void InitUndistortRectifyMap(
IntrinsicCameraParameters intrinsicParam,
Matrix<double> R,
Matrix<double> newCameraMatrix,
out Matrix<float> mapx,
out Matrix<float> mapy
)
{
mapx = new Matrix<float>(new Size(_imageWidth, _imageHeight));
mapy = new Matrix<float>(new Size(_imageWidth, _imageHeight));
CvInvoke.cvInitUndistortRectifyMap(intrinsicParam.IntrinsicMatrix.Ptr, intrinsicParam.DistortionCoeffs.Ptr, R.Ptr, newCameraMatrix.Ptr, mapx.Ptr, mapy.Ptr);
}
private void buttonTestCalc_Click(object sender, EventArgs e)
{
// Stereo Rectify images
Matrix<double> R1;
Matrix<double> R2;
Matrix<double> P1;
Matrix<double> P2;
Matrix<double> Q;
Rectangle validPixROI1, validPixROI2;
validPixROI1 = new Rectangle();
validPixROI2 = new Rectangle();
StereoRectify(_inPramsLeft, _inPramsRight, new Size(_imageWidth, _imageHeight), _outExtParamsStereo, out R1, out R2, out P1, out P2, out Q, 0, 0, new Size(_imageWidth, _imageHeight), ref validPixROI1, ref validPixROI2);
//InitUndistortRectifyMap(_inPramsLeft, R1, P1, out _mapxLeft, out _mapyLeft);
//InitUndistortRectifyMap(_inPramsRight, R2, P2, out _mapxRight, out _mapyRight);
_inPramsLeft.InitUndistortMap(_imageWidth, _imageHeight, out _mapxLeft, out _mapyLeft);
_inPramsRight.InitUndistortMap(_imageWidth, _imageHeight, out _mapxRight, out _mapyRight);
Image<Gray, byte> imgLeft = camLeft.lastFrameGray.Clone();
Image<Gray, byte> imgRight = camRight.lastFrameGray.Clone();
// **** THIS IS WHERE IM UP TO, no errors, it just hangs ****
CvInvoke.cvRemap(camLeft.lastFrameGray.Ptr, imgLeft.Ptr, _mapxLeft.Ptr, _mapyLeft.Ptr, (int)INTER.CV_INTER_LINEAR | (int)WARP.CV_WARP_FILL_OUTLIERS, new MCvScalar(0));
// StereoBM stereoSolver = new StereoBM(Emgu.CV.CvEnum.STEREO_BM_TYPE.BASIC, 0);
//stereoSolver.FindStereoCorrespondence(
}
public void PrintIntrinsic(IntrinsicCameraParameters CamIntrinsic)
{
// Prints the Intrinsic camera parameters to the command line
Console.WriteLine("Intrinsic Matrix:");
string outStr = "";
int i = 0;
int j = 0;
for (i = 0; i < CamIntrinsic.IntrinsicMatrix.Height; i++)
{
for (j = 0; j < CamIntrinsic.IntrinsicMatrix.Width; j++)
{
outStr = outStr + CamIntrinsic.IntrinsicMatrix.Data[i, j].ToString();
outStr = outStr + " ";
}
Console.WriteLine(outStr);
outStr = "";
}
Console.WriteLine("Distortion Coefficients: ");
outStr = "";
for (j = 0; j < CamIntrinsic.DistortionCoeffs.Height; j++)
{
outStr = outStr + CamIntrinsic.DistortionCoeffs.Data[j, 0].ToString();
outStr = outStr + " ";
}
Console.WriteLine(outStr);
}
public void PrintExtrinsic(ExtrinsicCameraParameters CamExtrinsic)
{
// Prints the Extrinsic camera parameters to the command line
Console.WriteLine("Extrinsic Matrix:");
string outStr = "";
int i = 0;
int j = 0;
for (i = 0; i < CamExtrinsic.ExtrinsicMatrix.Height; i++)
{
for (j = 0; j < CamExtrinsic.ExtrinsicMatrix.Width; j++)
{
outStr = outStr + CamExtrinsic.ExtrinsicMatrix.Data[i, j].ToString();
outStr = outStr + " ";
}
Console.WriteLine(outStr);
outStr = "";
}
Console.WriteLine("Rotation Vector: ");
outStr = "";
for (i = 0; i < CamExtrinsic.RotationVector.Height; i++)
{
for (j = 0; j < CamExtrinsic.RotationVector.Width; j++)
{
outStr = outStr + CamExtrinsic.RotationVector.Data[i, j].ToString();
outStr = outStr + " ";
}
Console.WriteLine(outStr);
outStr = "";
}
Console.WriteLine("Translation Vector: ");
outStr = "";
for (i = 0; i < CamExtrinsic.TranslationVector.Height; i++)
{
for (j = 0; j < CamExtrinsic.TranslationVector.Width; j++)
{
outStr = outStr + CamExtrinsic.TranslationVector.Data[i, j].ToString();
outStr = outStr + " ";
}
Console.WriteLine(outStr);
outStr = "";
}
}
}
}
TNKS!
Your maps must be images instead of matrices.
Specifically, of “Gray, float” type.