OpenCV第四章练习p126_1

 

#include <opencv/cv.h>
#include <opencv/highgui.h>

/* 显示灰度视频
int main(int argc, char *argv[])
{
    char src[] = "F:\\test\\p126_1\\p126_1\\tree.avi";
    CvCapture * capture = 0;
    IplImage * frame, *gray;

    capture = cvCreateFileCapture(src);
    if(capture == NULL)
    {
        cvNamedWindow("error",CV_WINDOW_AUTOSIZE);
        cvWaitKey(0);
        return 0;
    }
    while(1)
    {
        frame = cvQueryFrame(capture);
        if(frame == 0)
            break;
        gray = cvCreateImage(cvGetSize(frame),IPL_DEPTH_8U, 1);
        cvConvertImage(frame, gray, 1);
        cvNamedWindow("p126_1",CV_WINDOW_AUTOSIZE);
        cvShowImage("p126_1", gray);
        cvWaitKey(33);
    }

    cvReleaseImage(&frame);
    cvReleaseImage(&gray);
    cvReleaseCapture(&capture);
    cvDestroyWindow("p126_1");
}
*/

// 在一张图片上显示出来
int main(int argc, char *argv[])
{
    char src[] = "F:\\test\\p126_1\\p126_1\\tree.avi";
    CvCapture *capture = 0;
    IplImage *frame, *gray, *merge;
    IplImage *head1, *head2, *head3;
//    char *ptr_img_data;
//    int i, j, k;

    capture = cvCreateFileCapture(src);
    if(capture == NULL)
    {
        cvNamedWindow("error",CV_WINDOW_AUTOSIZE);
        cvWaitKey(0);
        return 0;
    }
    frame = cvQueryFrame(capture);
    merge = cvCreateImage(cvSize(3*frame->width, frame->height), IPL_DEPTH_8U, 3);
    head1 = cvCreateImage(cvSize(frame->width, frame->height), IPL_DEPTH_8U, 3);
    head2 = cvCreateImage(cvSize(frame->width, frame->height), IPL_DEPTH_8U, 3);
    head3 = cvCreateImage(cvSize(frame->width, frame->height), IPL_DEPTH_8U, 3);

    head1->widthStep = merge->widthStep;
    head1->imageData = merge->imageData;
    head2->widthStep = merge->widthStep;
    head2->imageData = merge->imageData + frame->width*frame->nChannels;
    head3->widthStep = merge->widthStep;
    head3->imageData = merge->imageData + frame->width*frame->nChannels*2;

    gray = cvCreateImage(cvGetSize(frame),IPL_DEPTH_8U, 1);
    cvConvertImage(frame, gray, 1);

/* 像素颜色取反
    ptr_img_data = frame->imageData;
    for(i=0; i<frame->height; i++)
        for(j=0; j<frame->width; j++)
            for(k=0; k<frame->nChannels; k++)
                ptr_img_data[i*frame->widthStep+j*frame->nChannels+k] =
                        255 - ptr_img_data[i*frame->widthStep+j*frame->nChannels+k];
*/
    cvConvertImage(frame, head1, 0);// 注释1
    cvConvertImage(gray, head2, 1);
    cvCanny(gray, gray, 0, 255, 3);
    cvConvertImage(gray, head3, 1);

    cvNamedWindow("p126_1",CV_WINDOW_AUTOSIZE);
    cvShowImage("p126_1", merge);
    cvWaitKey(0);

//    cvReleaseImage(&frame);   // 不能释放cvQueryFrame返回的图像指针
    cvReleaseImageHeader(&head1);
    cvReleaseImageHeader(&head2);
    cvReleaseImageHeader(&head3);
    cvReleaseImage(&gray);
    cvReleaseImage(&merge);
    cvReleaseCapture(&capture);
    cvDestroyWindow("p126_1");
}

运行结果：

在上面代码中，因为要判断视频文件是否已经打开了，而messagebox我不会调用，所以当错误是我打开一个窗口，标题为error：

上面代码中cvConvertImage(frame, head1, 0);一开始我传递的第三个参数是3，显示如下：

第一个图像翻转了，且颜色不对，后来发现，cvConvertImage函数的第三个参数flags是转换的模式，可以取0：没有变化；1：垂直翻转，即沿x轴翻转；2：交换红蓝信道；取3时相当1&2，所以即翻转又交换红蓝信道。