摄像头标定

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，也许需要图像增强处理。

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： 

代码下载

代码： <c>#include "stdafx.h"

1. include <stdio.h>
2. include <stdlib.h>
3. include <string.h>

// OpenCV

1. include <cxcore.h>
2. include <cv.h>
3. include <highgui.h>
4. 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...\n"); 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("\n");

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

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 ); } } </c>