《学习OpenCV》第四章课后题8

题目说明：
有趣的人脸程序。画一个骷髅头并保存在磁盘文件中。使之能读入骷髅头图像。
a、检测到人脸，便将人脸矩形区域中的图像用骷髅头图像代替。提示：cvConvertImage（）可以改变图像的大小，或者使用cvSize（）函数。可以将矩形区域设置成ROI，然后使用cvCopy（）复制缩放后的图像。
b、加入一个滑动条，在范围0.0~0.1之间设置10位置。使用滑动条来调节骷髅头与矩形区域内图像的alpha融合（使用cvAddweighted()函数）

#include <opencv/cv.h> #include <opencv/highgui.h>#include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <math.h> #include <float.h> #include <limits.h> #include <time.h> #include <ctype.h>/* Result window title */#define  WND_RESULT   "result"static CvMemStorage* storage = 0; static CvHaarClassifierCascade* cascade = 0;void detect_and_draw( IplImage* image );const char* cascade_name = "haarcascade_frontalface_alt.xml"; /* Skull image */IplImage* g_skullImage;/* Trackbar initial value */int g_trackbar_value = 5;/* Tackbar total values */int g_trackbar_total = 10;/* Alpha blend's alpha */double g_alpha = 0;/* Trackbar callback function */void switch_callback(int pos){    printf("Trackbar event.  pos: %d\n", pos);    g_alpha = (double)pos / g_trackbar_total;}int main( ) {     CvCapture* capture = cvCreateCameraCapture(0);    if(!capture)    {        printf("Camera error.\n");        return -1;    }    cascade_name = "haarcascade_frontalface_alt2.xml";     cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 );     if( !cascade )     {         printf( "ERROR: Could not load classifier cascade\n" );         return -1;     }     storage = cvCreateMemStorage(0);     cvNamedWindow( WND_RESULT, 1 );     cvWaitKey(1000);    IplImage* frame = cvQueryFrame(capture);    if(!frame)    {        return -1;    }    // Load skull image    IplImage* skullImage = cvLoadImage("F:/试验数据/kull2.jpg", CV_LOAD_IMAGE_UNCHANGED);    if(!skullImage)    {        printf("ERROR: Can't load skull image.\n");        return -1;    }    g_skullImage = cvCreateImage(cvGetSize(skullImage), skullImage->depth, 3);    if(skullImage->nChannels != 3)    {        cvCvtColor(skullImage, g_skullImage, CV_GRAY2BGR);    }    else    {        cvCopy(skullImage, g_skullImage);    }    // Create trackbar    cvCreateTrackbar("Switch", WND_RESULT, &g_trackbar_value, g_trackbar_total, switch_callback );    // Initialize Alpha-Blend's alpha    g_alpha = (double)g_trackbar_value / g_trackbar_total;    char c;    while( 1 )     {         frame = cvQueryFrame(capture);        if(!frame)        {            return -1;        }        detect_and_draw( frame );         c = cvWaitKey(50);        if(c == 27)        {            break;        }    }    cvDestroyWindow(WND_RESULT);     cvReleaseImage(&frame);    cvReleaseCapture(&capture);    cvReleaseImage(&skullImage);    cvReleaseImage(&g_skullImage);    return 0; }void detect_and_draw(IplImage* img ) {     double scale=1.2;     static CvScalar colors[] = {         {{0,0,255}},{{0,128,255}},{{0,255,255}},{{0,255,0}},         {{255,128,0}},{{255,255,0}},{{255,0,0}},{{255,0,255}}     };//Just some pretty colors to draw with    //Image Preparation     //     IplImage* gray = cvCreateImage(cvSize(img->width,img->height),8,1);     IplImage* small_img=cvCreateImage(cvSize(cvRound(img->width/scale),cvRound(img->height/scale)),8,1);     cvCvtColor(img,gray, CV_BGR2GRAY);     cvResize(gray, small_img, CV_INTER_LINEAR);    cvEqualizeHist(small_img,small_img); //直方图均衡    //Detect objects if any     //     cvClearMemStorage(storage);     double t = (double)cvGetTickCount();     CvSeq* objects = cvHaarDetectObjects(small_img,         cascade,         storage,         1.1,         2,         0/*CV_HAAR_DO_CANNY_PRUNING*/,         cvSize(30,30));    t = (double)cvGetTickCount() - t;     printf( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) );    //Loop through found objects and draw boxes around them     for(int i=0;i<(objects? objects->total:0);++i)     {         CvRect* r=(CvRect*)cvGetSeqElem(objects,i);         CvRect r_scale = cvRect( r->x * scale, r->y * scale, r->width * scale, r->height * scale );        // 改变骷髅头图像大小        IplImage * skullResize = cvCreateImage( cvSize(r_scale.width, r_scale.height),            g_skullImage->depth, g_skullImage->nChannels );        cvResize(g_skullImage, skullResize, CV_INTER_LINEAR);        // 将人脸检测区域用骷髅头图像代替        cvSetImageROI(img, r_scale);        // b -- Alpha blend         printf("Alpha: %f\t", g_alpha);        cvAddWeighted( img, g_alpha, skullResize, 1.0 - g_alpha, 0.0, img);       /* This is a part        cvCopy(skullResize, img); */        cvResetImageROI(img);        cvReleaseImage(&skullResize);    }     cvShowImage( WND_RESULT, img );     cvReleaseImage(&gray);     cvReleaseImage(&small_img); }

注：加入cvWaitKey（1000）是为了能让摄像机捕捉到图像，程序将捕捉后的图像缩放，然后进行人脸识别（为了加快速度），然后在显示的时候又恢复原始图像的大小（乘以之前的缩放系数）
其他：发现cvLoad返回的是空型指针，故可以将其强行转换成其他类型，这里学习了。

引用：qdsclove的专栏
http://blog.csdn.net/stk_overflow/article/details/12299963