鸟瞰图实现代码--opencv

鸟瞰图变换实例

本文为《学习opencv（中文版）》第十二章第一个例子：鸟瞰图，原书上的第445页的代码是可以运行的，只是书中没有把输入的参数写清楚，需要自己动手。

• 1. mian()的参数，argc和argv说明

• 2. 本例中argv【1】~argv【5】的具体值

• 3. 代码展示

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1. main()的参数，argc和argv的说明

argc和argv这两个参数一般在用命令行编译程序时有用，int类型的argc，用来统计程序运行时发送给main函数的命令行参数的个数，char *类型的argv[]，为字符串数组，用来存放指向的字符串擦数的指针数组，每个元素指向一个参数。各成员含义：
- argv[0]指向成员运行的全路径名,
- argv[1 ]指向在dos命令行中执行程序名后的第一个字符串,
- argv[2 ]指向执行程序名后的第二个字符串,
- argv[3 ]指向执行程序名后的第三个字符串
- ……
在vs中argv的值对应于【项目】->【属性】->【配置属性】->【调试】->【命令参数】中的值。如果有多个字符串，则用空格隔开，argv[0]不需要输入，命令参数中的值从argv[1 ]开始。—— 《opencv3编程入门》（毛星云，冷雪飞等著）。

2.本例中argv【1】~argv【5】的具体值

argv[1 ]=12 //棋盘内点长
argv[2 ]=12 //棋盘内点宽
argv[3 ]=Intrinsics.xml //摄像机的内参数矩阵
argv[4 ]=Distortion.xml //摄像机的畸变系数
argv[5 ]=0.jpg //图片名
参数三和参数四是两个文件，文件由《学习opencv》第十一章的一次完成标定程序生成的，

3. 代码展示

#include 
#include 
#include 
#include 

void help(){
    printf("Birds eye view\n\n"
            "  birdseye board_w board_h intrinsics_mat.xml distortion_mat.xml checker_image \n\n"
            "Where: board_{w,h}    are the # of internal corners in the checkerboard\n"
            "       intrinsic      intrinsic path/name of matrix from prior calibration\n"
            "       distortion     distortion path/name of matrix from pror calibration\n"
            "       checker_image  is the path/name of image of checkerboard on the plane \n"
            "                      Frontal view of this will be shown.\n\n"
            " ADJUST VIEW HEIGHT using keys 'u' up, 'd' down. ESC to quit.\n\n");
}

int main(int argc, char* argv[]) {
    if(argc!=6)
        return -1;
    help();
    //INPUT PARAMETERS:
    int board_w = atoi(argv[1]);
    int board_h = atoi(argv[2]);
    int board_n  = board_w * board_h;
    CvSize board_sz = cvSize( board_w, board_h );
    CvMat *intrinsic = (CvMat*)cvLoad(argv[3]);
    CvMat *distortion = (CvMat*)cvLoad(argv[4]);
    IplImage *image = 0, *gray_image = 0;
    if((image = cvLoadImage(argv[5]))== 0){
        printf("Error: Couldn't load %s\n",argv[5]);
        return -1;
    }
    gray_image = cvCreateImage(cvGetSize(image),8,1);
    cvCvtColor(image, gray_image, CV_BGR2GRAY);

    //UNDISTORT OUR IMAGE
    IplImage* mapx = cvCreateImage( cvGetSize(image), IPL_DEPTH_32F, 1 );
    IplImage* mapy = cvCreateImage( cvGetSize(image), IPL_DEPTH_32F, 1 );
    cvInitUndistortMap(
      intrinsic,
      distortion,
      mapx,
      mapy
    );
    IplImage *t = cvCloneImage(image);
    cvRemap( t, image, mapx, mapy );

    //GET THE CHECKERBOARD ON THE PLANE
    cvNamedWindow("Checkers");
    CvPoint2D32f* corners = new CvPoint2D32f[ board_n ];
    int corner_count = 0;
    int found = cvFindChessboardCorners(
        image,
        board_sz,
        corners,
        &corner_count, 
        CV_CALIB_CB_ADAPTIVE_THRESH | CV_CALIB_CB_FILTER_QUADS
      );
    if(!found){
        printf("Couldn't aquire checkerboard on %s, only found %d of %d corners\n",
                argv[5],corner_count,board_n);
        return -1;
    }
    //Get Subpixel accuracy on those corners
    cvFindCornerSubPix(gray_image, corners, corner_count, 
              cvSize(11,11),cvSize(-1,-1), 
              cvTermCriteria( CV_TERMCRIT_EPS+CV_TERMCRIT_ITER, 30, 0.1 ));

    //GET THE IMAGE AND OBJECT POINTS:
    //Object points are at (r,c): (0,0), (board_w-1,0), (0,board_h-1), (board_w-1,board_h-1)
    //That means corners are at: corners[r*board_w + c]
    CvPoint2D32f objPts[4], imgPts[4];
    objPts[0].x = 0;         objPts[0].y = 0; 
    objPts[1].x = board_w-1; objPts[1].y = 0; 
    objPts[2].x = 0;         objPts[2].y = board_h-1;
    objPts[3].x = board_w-1; objPts[3].y = board_h-1; 
    imgPts[0] = corners[0];
    imgPts[1] = corners[board_w-1];
    imgPts[2] = corners[(board_h-1)*board_w];
    imgPts[3] = corners[(board_h-1)*board_w + board_w-1];

    //DRAW THE POINTS in order: B,G,R,YELLOW
    cvCircle(image,cvPointFrom32f(imgPts[0]),9,CV_RGB(0,0,255),3);
    cvCircle(image,cvPointFrom32f(imgPts[1]),9,CV_RGB(0,255,0),3);
    cvCircle(image,cvPointFrom32f(imgPts[2]),9,CV_RGB(255,0,0),3);
    cvCircle(image,cvPointFrom32f(imgPts[3]),9,CV_RGB(255,255,0),3);

    //DRAW THE FOUND CHECKERBOARD
    cvDrawChessboardCorners(image, board_sz, corners, corner_count, found);
    IplImage *image_temp = cvCreateImage(cvSize(image->width/2, image->height/2),image->depth,image->nChannels);
    cvResize(image, image_temp);
    cvShowImage( "Checkers", image_temp );

    //FIND THE HOMOGRAPHY
    CvMat *H = cvCreateMat( 3, 3, CV_32F);
    CvMat *H_invt = cvCreateMat(3,3,CV_32F);
    cvGetPerspectiveTransform(objPts,imgPts,H);

    //LET THE USER ADJUST THE Z HEIGHT OF THE VIEW
    float Z = 25;
    int key = 0;
    IplImage *birds_image = cvCloneImage(image);
    cvNamedWindow("Birds_Eye");
    while(key != 27) {//escape key stops
       CV_MAT_ELEM(*H,float,2,2) = Z;
//     cvInvert(H,H_invt); //If you want to invert the homography directly
//     cvWarpPerspective(image,birds_image,H_invt,CV_INTER_LINEAR+CV_WARP_FILL_OUTLIERS );
       //USE HOMOGRAPHY TO REMAP THE VIEW
       cvWarpPerspective(image,birds_image,H,
            CV_INTER_LINEAR+CV_WARP_INVERSE_MAP+CV_WARP_FILL_OUTLIERS );
       IplImage *birds_image1 = cvCreateImage(cvSize(birds_image->width/2, birds_image->height/2),birds_image->depth,birds_image->nChannels);
       cvResize(birds_image, birds_image1);
       cvShowImage("Birds_Eye", birds_image1);
       key = cvWaitKey();
       if(key == 'u') Z += 0.5;
       if(key == 'd') Z -= 0.5;
    }

    //SHOW ROTATION AND TRANSLATION VECTORS
    CvMat* image_points  = cvCreateMat(4,1,CV_32FC2);
    CvMat* object_points = cvCreateMat(4,1,CV_32FC3);
    for(int i=0;i<4;++i){
        CV_MAT_ELEM(*image_points,CvPoint2D32f,i,0) = imgPts[i];
        CV_MAT_ELEM(*object_points,CvPoint3D32f,i,0) = cvPoint3D32f(objPts[i].x,objPts[i].y,0);
    }

    CvMat *RotRodrigues   = cvCreateMat(3,1,CV_32F);
    CvMat *Rot   = cvCreateMat(3,3,CV_32F);
    CvMat *Trans = cvCreateMat(3,1,CV_32F);
    cvFindExtrinsicCameraParams2(object_points,image_points,
            intrinsic,distortion,
            RotRodrigues,Trans);
    cvRodrigues2(RotRodrigues,Rot);

    //SAVE AND EXIT
    cvSave("Rot.xml",Rot);
    cvSave("Trans.xml",Trans);
    cvSave("H.xml",H);
    cvInvert(H,H_invt);
    cvSave("H_invt.xml",H_invt); //Bottom row of H invert is horizon line
    return 0;
}

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