camera calibration 摄像头标定 代码整理（2007－2－6 修正）

这里介绍了一个使用directshow标定与Matlab的示例，写的很详细。

 http://w3.impa.br/~pcezar/3dp/original/CVL_html/appPage/doc_calib.html#Tutorial

 

OPENCV没有提供完整的示例，自己整理了一下，贴出来记录。

步骤如下：

首先自制一张标定图片，用A4纸打印出来，设定距离，再设定标定棋盘的格子数目，如8×6，以下是我做的图片8×8

然后利用cvFindChessboardCorners找到棋盘在摄像头中的2D位置，这里cvFindChessboardCorners不太稳定，有时不能工作。

计算实际的距离，应该是3D的距离。我设定为21.6毫米，既在A4纸上为两厘米。

再用cvCalibrateCamera2计算内参，

最后用cvUndistort2纠正图像的变形。

结果如下：

 

源代码如下：

 

#include  " stdafx.h "
#include  < stdio.h >
#include  < stdlib.h >
#include  < string .h >
//  OpenCV
#include  < cxcore.h >
#include  < cv.h >
#include  < highgui.h >
#include  < cvaux.h >


void  InitCorners3D(CvMat  * Corners3D, CvSize ChessBoardSize,  int  Nimages,  float  SquareSize);
void  makeChessBoard();
int  myFindChessboardCorners(  const   void *  image, CvSize pattern_size,
                             CvPoint2D32f *  corners,  int *  corner_count = NULL,
                              int  flags = CV_CALIB_CB_ADAPTIVE_THRESH );


inline  int  drawCorssMark(IplImage  * dst,CvPoint pt)
/**/ /*************************************************
  Function:        main_loop
  Description:     绘制一个十字标记                    
  Calls:          
  Called By:      
  Input:           RGB image,  pt               
  Output:         
  Return:         
  Others:          需要检查坐标是否越界 to do list
*************************************************/
... {
    
    const int cross_len = 4;
    CvPoint pt1,pt2,pt3,pt4;
    pt1.x = pt.x;
    pt1.y = pt.y - cross_len;
    pt2.x = pt.x;
    pt2.y = pt.y + cross_len;
    pt3.x = pt.x - cross_len;
    pt3.y = pt.y;
    pt4.x = pt.x + cross_len;
    pt4.y = pt.y;

    cvLine(dst,pt1,pt2,CV_RGB(0,255,0),2,CV_AA, 0 );    
    cvLine(dst,pt3,pt4,CV_RGB(0,255,0),2,CV_AA, 0 );
    
    return 0;
}

/**/ /* declarations for OpenCV */
IplImage                  * current_frame_rgb,grid;
IplImage                  * current_frame_gray;
IplImage                  * chessBoard_Img;

int                        Thresholdness  =   120 ;

int  image_width  =   320 ;
int  image_height  =   240 ;

bool  verbose  =   false ;

const   int  ChessBoardSize_w  =   7 ;
const   int  ChessBoardSize_h  =   7 ;
//  Calibration stuff
bool             calibration_done  =   false ;
const  CvSize     ChessBoardSize  =  cvSize(ChessBoardSize_w,ChessBoardSize_h);
// float             SquareWidth = 21.6f;  // 实际距离 毫米单位 在A4纸上为两厘米
float              SquareWidth  =   17 ;  // 投影实际距离 毫米单位  200

const     int  NPoints  =  ChessBoardSize_w * ChessBoardSize_h;
const     int  NImages  =   20 ;  // Number of images to collect 

CvPoint2D32f corners[NPoints * NImages];
int  corner_count[NImages]  =   ... {0} ;
int  captured_frames  =   0 ;

CvMat  * intrinsics;
CvMat  * distortion_coeff;
CvMat  * rotation_vectors;
CvMat  * translation_vectors;
CvMat  * object_points;
CvMat  * point_counts;
CvMat  * image_points;
int  find_corners_result  = 0  ;


void  on_mouse(  int   event ,  int  x,  int  y,  int  flags,  void *  param )
... {

    if( event == CV_EVENT_LBUTTONDOWN )
    ...{
        //calibration_done = true; 
    }
}


int  main( int  argc,  char   * argv[])
... {


  CvFont font;
  cvInitFont( &font, CV_FONT_VECTOR0,5, 5, 0, 7, 8);
  
  intrinsics         = cvCreateMat(3,3,CV_32FC1);
  distortion_coeff     = cvCreateMat(1,4,CV_32FC1);
  rotation_vectors     = cvCreateMat(NImages,3,CV_32FC1);
  translation_vectors     = cvCreateMat(NImages,3,CV_32FC1);

  point_counts         = cvCreateMat(NImages,1,CV_32SC1);

  object_points     = cvCreateMat(NImages*NPoints,3,CV_32FC1);
  image_points         = cvCreateMat(NImages*NPoints,2,CV_32FC1);


  // Function to fill in the real-world points of the checkerboard
  InitCorners3D(object_points, ChessBoardSize, NImages, SquareWidth);


  CvCapture* capture = 0;

  
  if( argc == 1 || (argc == 2 && strlen(argv[1]) == 1 && isdigit(argv[1][0])))
      capture = cvCaptureFromCAM( argc == 2 ? argv[1][0] - '0' : 0 );
  else if( argc == 2 )
      capture = cvCaptureFromAVI( argv[1] );

  if( !capture )
  ...{
      fprintf(stderr,"Could not initialize capturing... ");
      return -1;
  }
  
  
  // Initialize all of the IplImage structures
  current_frame_rgb = cvCreateImage(cvSize(image_width, image_height), IPL_DEPTH_8U, 3);
  
  IplImage *current_frame_rgb2 = cvCreateImage(cvSize(image_width, image_height), IPL_DEPTH_8U, 3);
  current_frame_gray = cvCreateImage(cvSize(image_width, image_height), IPL_DEPTH_8U, 1);

  chessBoard_Img   = cvCreateImage(cvSize(image_width, image_height), IPL_DEPTH_8U, 3);  
  current_frame_rgb2->origin = chessBoard_Img->origin  = current_frame_gray->origin = current_frame_rgb->origin = 1;
  
  makeChessBoard();

  cvNamedWindow( "result", 0);
  cvNamedWindow( "Window 0", 0);
  cvNamedWindow( "grid", 0);
  cvMoveWindow( "grid", 100,100);
  cvSetMouseCallback( "Window 0", on_mouse, 0 );  
  cvCreateTrackbar("Thresholdness","Window 0",&Thresholdness, 255,0);
  
  while (!calibration_done)
  ...{

    while (captured_frames < NImages)
    ...{
      current_frame_rgb = cvQueryFrame( capture );
      //current_frame_rgb = cvLoadImage( "c:/BoardStereoL3.jpg" );
      //cvCopy(chessBoard_Img,current_frame_rgb);

      if( !current_frame_rgb )
          break;

      cvCopy(current_frame_rgb,current_frame_rgb2);
      cvCvtColor(current_frame_rgb, current_frame_gray, CV_BGR2GRAY);
      //cvThreshold(current_frame_gray,current_frame_gray,Thresholdness,255,CV_THRESH_BINARY);
      //cvThreshold(current_frame_gray,current_frame_gray,150,255,CV_THRESH_BINARY_INV);

/**//*
    int pos = 1;
    IplConvKernel* element = 0;
    const int element_shape = CV_SHAPE_ELLIPSE;
    element = cvCreateStructuringElementEx( pos*2+1, pos*2+1, pos, pos, element_shape, 0 );
    cvDilate(current_frame_gray,current_frame_gray,element,1);
    cvErode(current_frame_gray,current_frame_gray,element,1);
    cvReleaseStructuringElement(&element);
*/
    
    find_corners_result = cvFindChessboardCorners(current_frame_gray,
                                          ChessBoardSize,
                                          &corners[captured_frames*NPoints],
                                          &corner_count[captured_frames],
                                          0);



    cvDrawChessboardCorners(current_frame_rgb2, ChessBoardSize, &corners[captured_frames*NPoints], NPoints, find_corners_result);


    cvShowImage("Window 0",current_frame_rgb2);
    cvShowImage("grid",chessBoard_Img);

    if(find_corners_result==1)
    ...{
        cvWaitKey(2000);
        cvSaveImage("c:/hardyinCV.jpg",current_frame_rgb2);
        captured_frames++;
    }
    //cvShowImage("result",current_frame_gray);

    intrinsics->data.fl[0] = 256.8093262;   //fx        
    intrinsics->data.fl[2] = 160.2826538;   //cx
    intrinsics->data.fl[4] = 254.7511139;   //fy
    intrinsics->data.fl[5] = 127.6264572;   //cy

    intrinsics->data.fl[1] = 0;   
    intrinsics->data.fl[3] = 0;   
    intrinsics->data.fl[6] = 0;   
    intrinsics->data.fl[7] = 0;   
    intrinsics->data.fl[8] = 1;       

    distortion_coeff->data.fl[0] = -0.193740;  //k1
    distortion_coeff->data.fl[1] = -0.378588;  //k2
    distortion_coeff->data.fl[2] = 0.028980;   //p1
    distortion_coeff->data.fl[3] = 0.008136;   //p2

    cvWaitKey(40);
    find_corners_result = 0;
    }   
    //if (find_corners_result !=0)
    ...{

        printf(" ");

        cvSetData( image_points, corners, sizeof(CvPoint2D32f));
        cvSetData( point_counts, &corner_count, sizeof(int));

        
        cvCalibrateCamera2( object_points,
            image_points,
            point_counts,
            cvSize(image_width,image_height),
            intrinsics,
            distortion_coeff,
            rotation_vectors,
            translation_vectors,
            0);
        

        // [fx 0 cx; 0 fy cy; 0 0 1].
        cvUndistort2(current_frame_rgb,current_frame_rgb,intrinsics,distortion_coeff);
        cvShowImage("result",current_frame_rgb);


        float intr[3][3] = ...{0.0};
        float dist[4] = ...{0.0};
        float tranv[3] = ...{0.0};
        float rotv[3] = ...{0.0};

        for ( int i = 0; i < 3; i++)
        ...{
            for ( int j = 0; j < 3; j++)
            ...{
                intr[i][j] = ((float*)(intrinsics->data.ptr + intrinsics->step*i))[j];
            }
            dist[i] = ((float*)(distortion_coeff->data.ptr))[i];
            tranv[i] = ((float*)(translation_vectors->data.ptr))[i];
            rotv[i] = ((float*)(rotation_vectors->data.ptr))[i];
        }
        dist[3] = ((float*)(distortion_coeff->data.ptr))[3];

        printf("----------------------------------------- ");
        printf("INTRINSIC MATRIX:  ");
        printf("[ %6.4f %6.4f %6.4f ]  ", intr[0][0], intr[0][1], intr[0][2]);
        printf("[ %6.4f %6.4f %6.4f ]  ", intr[1][0], intr[1][1], intr[1][2]);
        printf("[ %6.4f %6.4f %6.4f ]  ", intr[2][0], intr[2][1], intr[2][2]);
        printf("----------------------------------------- ");
        printf("DISTORTION VECTOR:  ");
        printf("[ %6.4f %6.4f %6.4f %6.4f ]  ", dist[0], dist[1], dist[2], dist[3]);
        printf("----------------------------------------- ");
        printf("ROTATION VECTOR:  ");
        printf("[ %6.4f %6.4f %6.4f ]  ", rotv[0], rotv[1], rotv[2]);
        printf("TRANSLATION VECTOR:  ");
        printf("[ %6.4f %6.4f %6.4f ]  ", tranv[0], tranv[1], tranv[2]);
        printf("----------------------------------------- ");

        cvWaitKey(0);

        calibration_done = true;      
    }
               
  }

  exit(0);
  cvDestroyAllWindows();
}

void  InitCorners3D(CvMat  * Corners3D, CvSize ChessBoardSize,  int  NImages,  float  SquareSize)
... {
  int CurrentImage = 0;
  int CurrentRow = 0;
  int CurrentColumn = 0;
  int NPoints = ChessBoardSize.height*ChessBoardSize.width;
  float * temppoints = new float[NImages*NPoints*3];

  // for now, assuming we're row-scanning
  for (CurrentImage = 0 ; CurrentImage < NImages ; CurrentImage++)
  ...{
    for (CurrentRow = 0; CurrentRow < ChessBoardSize.height; CurrentRow++)
    ...{
      for (CurrentColumn = 0; CurrentColumn < ChessBoardSize.width; CurrentColumn++)
      ...{
          temppoints[(CurrentImage*NPoints*3)+(CurrentRow*ChessBoardSize.width + CurrentColumn)*3]=(float)CurrentRow*SquareSize;
          temppoints[(CurrentImage*NPoints*3)+(CurrentRow*ChessBoardSize.width + CurrentColumn)*3+1]=(float)CurrentColumn*SquareSize;
          temppoints[(CurrentImage*NPoints*3)+(CurrentRow*ChessBoardSize.width + CurrentColumn)*3+2]=0.f;
      }
    }
  }
  (*Corners3D) = cvMat(NImages*NPoints,3,CV_32FC1, temppoints);
}

int  myFindChessboardCorners(  const   void *  image, CvSize pattern_size,
                             CvPoint2D32f *  corners,  int *  corner_count,
                              int  flags )

... {


    IplImage* eig = cvCreateImage( cvGetSize(image), 32, 1 );
    IplImage* temp = cvCreateImage( cvGetSize(image), 32, 1 );
    double quality = 0.01;
    double min_distance = 5;
    int win_size =10;

    int count = pattern_size.width * pattern_size.height;
    cvGoodFeaturesToTrack( image, eig, temp, corners, &count,
        quality, min_distance, 0, 3, 0, 0.04 );
    cvFindCornerSubPix( image, corners, count,
        cvSize(win_size,win_size), cvSize(-1,-1),
        cvTermCriteria(CV_TERMCRIT_ITER|CV_TERMCRIT_EPS,20,0.03));
    
    cvReleaseImage( &eig );
    cvReleaseImage( &temp );

    return 1;
}

void  makeChessBoard()
... {

  CvScalar e; 
  e.val[0] =255;
  e.val[1] =255;
  e.val[2] =255;
  cvSet(chessBoard_Img,e,0);
  for(int i = 0;i<ChessBoardSize.width+1;i++)
      for(int j = 0;j<ChessBoardSize.height+1;j++)
      ...{
          int w =(image_width)/2/(ChessBoardSize.width);
          int h = w; //(image_height)/2/(ChessBoardSize.height);

          int ii = i+1;
          int iii = ii+1;
          int jj =j+1;
          int jjj =jj+1;
          int s_x = image_width/6;          

        if((i+j)%2==1)
           cvRectangle( chessBoard_Img, cvPoint(w*i+s_x,h*j+s_x),cvPoint(w*ii-1+s_x,h*jj-1+s_x), CV_RGB(0,0,0),CV_FILLED, 8, 0 );
      }
}