OpenCV学习之椭圆曲线拟合

程序首先发现图像的轮廓，然后用椭圆逼近它。

//椭圆曲线拟合
#include "cv.h"
#include "highgui.h"
int slider_pos = 70;
IplImage *image02 = 0, *image03 = 0, *image04 = 0;
void process_image(int h);
int main(int argc, char** argv)
{
    // 读入图像，强制为灰度图像
    image03 = cvLoadImage("corner.tif", 0);
    // Create the destination images
    image02 = cvCloneImage(image03);
    image04 = cvCloneImage(image03);
    // Create windows.
    cvNamedWindow("Source", 1);
    cvNamedWindow("Result", 1);
    // Show the image.
    cvShowImage("Source", image03);
    // Create toolbars. HighGUI use.
    cvCreateTrackbar("Threshold", "Result", &slider_pos, 255, process_image);
    process_image(0);
    // Wait for a key stroke; the same function arranges events processing                
    cvWaitKey(0);
    cvReleaseImage(&image02);
    cvReleaseImage(&image03);
    cvDestroyWindow("Source");
    cvDestroyWindow("Result");
    return 0;
}
// Define trackbar callback functon. This function find contours,
// draw it and approximate it by ellipses.
void process_image(int h)
{
    CvMemStorage* stor;
    CvSeq* cont;
    CvBox2D32f* box;
    CvPoint* PointArray;
    CvPoint2D32f* PointArray2D32f;

    // 创建动态结构序列
    stor = cvCreateMemStorage(0);
    cont = cvCreateSeq(CV_SEQ_ELTYPE_POINT, sizeof(CvSeq), sizeof(CvPoint), stor);

    // 二值话图像.
    cvThreshold(image03, image02, slider_pos, 255, CV_THRESH_BINARY);

    // 寻找所有轮廓.
    cvFindContours(image02, stor, &cont, sizeof(CvContour),
        CV_RETR_LIST, CV_CHAIN_APPROX_NONE, cvPoint(0, 0));

    // Clear images. IPL use.
    cvZero(image02);
    cvZero(image04);

    // 本循环绘制所有轮廓并用椭圆拟合.
    for (; cont; cont = cont->h_next)
    {
        int i; // Indicator of cycle.
        int count = cont->total; // This is number point in contour
        CvPoint center;
        CvSize size;

        // Number point must be more than or equal to 6 (for cvFitEllipse_32f).        
        if (count < 6)
            continue;

        // Alloc memory for contour point set.    
        PointArray = (CvPoint*)malloc(count * sizeof(CvPoint));
        PointArray2D32f = (CvPoint2D32f*)malloc(count * sizeof(CvPoint2D32f));

        // Alloc memory for ellipse data.
        box = (CvBox2D32f*)malloc(sizeof(CvBox2D32f));

        // Get contour point set.
        cvCvtSeqToArray(cont, PointArray, CV_WHOLE_SEQ);

        // Convert CvPoint set to CvBox2D32f set.
        for (i = 0; i<count; i++)
        {
            PointArray2D32f[i].x = (float)PointArray[i].x;
            PointArray2D32f[i].y = (float)PointArray[i].y;
        }

        //拟合当前轮廓.
        cvFitEllipse(PointArray2D32f, count, box);

        // 绘制当前轮廓.
        cvDrawContours(image04, cont, CV_RGB(255, 255, 255),
            CV_RGB(255, 255, 255), 0, 1, 8, cvPoint(0, 0));

        // Convert ellipse data from float to integer representation.
        center.x = cvRound(box->center.x);
        center.y = cvRound(box->center.y);
        size.width = cvRound(box->size.width*0.5);
        size.height = cvRound(box->size.height*0.5);
        box->angle = -box->angle;

        // Draw ellipse.
        cvEllipse(image04, center, size,
            box->angle, 0, 360,
            CV_RGB(0, 0, 255), 1, CV_AA, 0);

        // Free memory.          
        free(PointArray);
        free(PointArray2D32f);
        free(box);
    }

    // Show image. HighGUI use.
    cvShowImage("Result", image04);
}