这道题是利用OpenCV例子程序里自带的人脸检测程序，做点图像的复制操作以及alpha融合。
说明：人脸检测的程序我参照了网上现有的例子程序，没有用我用的OpenCV版本（2.4.5）的facedetect.c，人脸检测部分是一个月前写的程序，这次做了点改动，以前的部分注释了起来。
代码：
1 #include <opencv/cv.h>
2 #include <opencv/highgui.h>
3 #include <opencv_libs.h>
4
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8 #include <assert.h>
9 #include <math.h>
10 #include <float.h>
11 #include <limits.h>
12 #include <time.h>
13 #include <ctype.h>
14
15 /*
16 *《学习OpenCV》第四章第八题
17 * 完成时间：3:43 10/5 星期六 2013
18 * 作者：qdsclove@163.com
19 */
20
21
22 /* Result window title */
23 #define WND_RESULT "result"
24
25 static CvMemStorage* storage = 0;
26 static CvHaarClassifierCascade* cascade = 0;
27
28 void detect_and_draw( IplImage* image );
29
30 const char* cascade_name =
31 "haarcascade_frontalface_alt.xml";
32
33 /* Skull image */
34 IplImage* g_skullImage;
35
36 /* Trackbar initial value */
37 int g_trackbar_value = 5;
38 /* Tackbar total values */
39 int g_trackbar_total = 10;
40
41 /* Alpha blend's alpha */
42 double g_alpha = 0;
43
44 /* Trackbar callback function */
45 void switch_callback(int pos)
46 {
47 printf("Trackbar event. pos: %d\n", pos);
48 g_alpha = (double)pos / g_trackbar_total;
49 }
50
51 int main( )
52 {
53 CvCapture* capture = cvCreateCameraCapture(0);
54 if(!capture)
55 {
56 printf("Camera error.\n");
57 return -1;
58 }
59 cascade_name = "haarcascade_frontalface_alt2.xml";
60 cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 );
61
62 if( !cascade )
63 {
64 printf( "ERROR: Could not load classifier cascade\n" );
65 return -1;
66 }
67
68 storage = cvCreateMemStorage(0);
69 cvNamedWindow( WND_RESULT, 1 );
70
71 IplImage* frame = cvQueryFrame(capture);
72 if(!frame)
73 {
74 return -1;
75 }
76
77 // Load skull image
78 IplImage* skullImage = cvLoadImage("skull.jpg", CV_LOAD_IMAGE_UNCHANGED);
79 if(!skullImage)
80 {
81 printf("ERROR: Can't load skull image.\n");
82 return -1;
83 }
84 g_skullImage = cvCreateImage(cvGetSize(skullImage), skullImage->depth, 3);
85 if(skullImage->nChannels != 3)
86 {
87 cvCvtColor(skullImage, g_skullImage, CV_GRAY2BGR);
88 }
89 else
90 {
91 cvCopy(skullImage, g_skullImage);
92 }
93
94 // Create trackbar
95 cvCreateTrackbar("Switch", WND_RESULT, &g_trackbar_value,
96 g_trackbar_total, switch_callback );
97 // Initialize Alpha-Blend's alpha
98 g_alpha = (double)g_trackbar_value / g_trackbar_total;
99
100 char c;
101 while( 1 )
102 {
103 frame = cvQueryFrame(capture);
104 if(!frame)
105 {
106 return -1;
107 }
108
109 detect_and_draw( frame );
110
111 c = cvWaitKey(50);
112 if(c == 27)
113 {
114 break;
115 }
116 }
117
118 cvDestroyWindow(WND_RESULT);
119 cvReleaseImage(&frame);
120 cvReleaseCapture(&capture);
121 cvReleaseImage(&skullImage);
122 cvReleaseImage(&g_skullImage);
123
124 return 0;
125 }
126
127
128 void detect_and_draw(IplImage* img )
129 {
130 double scale=1.2;
131 static CvScalar colors[] = {
132 {{0,0,255}},{{0,128,255}},{{0,255,255}},{{0,255,0}},
133 {{255,128,0}},{{255,255,0}},{{255,0,0}},{{255,0,255}}
134 };//Just some pretty colors to draw with
135
136 //Image Preparation
137 //
138 IplImage* gray = cvCreateImage(cvSize(img->width,img->height),8,1);
139 IplImage* small_img=cvCreateImage(cvSize(cvRound(img->width/scale),cvRound(img->height/scale)),8,1);
140 cvCvtColor(img,gray, CV_BGR2GRAY);
141 cvResize(gray, small_img, CV_INTER_LINEAR);
142
143 cvEqualizeHist(small_img,small_img); //直方图均衡
144
145 //Detect objects if any
146 //
147 cvClearMemStorage(storage);
148 double t = (double)cvGetTickCount();
149 CvSeq* objects = cvHaarDetectObjects(small_img,
150 cascade,
151 storage,
152 1.1,
153 2,
154 0/*CV_HAAR_DO_CANNY_PRUNING*/,
155 cvSize(30,30));
156
157 t = (double)cvGetTickCount() - t;
158 printf( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) );
159
160 //Loop through found objects and draw boxes around them
161 for(int i=0;i<(objects? objects->total:0);++i)
162 {
163 CvRect* r=(CvRect*)cvGetSeqElem(objects,i);
164
165 CvRect r_scale = cvRect( r->x * scale, r->y * scale, r->width * scale, r->height * scale );
166 // 改变骷髅头图像大小
167 IplImage * skullResize = cvCreateImage( cvSize(r_scale.width, r_scale.height),
168 g_skullImage->depth, g_skullImage->nChannels );
169 cvResize(g_skullImage, skullResize, CV_INTER_LINEAR);
170
171 // 将人脸检测区域用骷髅头图像代替
172 cvSetImageROI(img, r_scale);
173 // b -- Alpha blend
174 printf("Alpha: %f\t", g_alpha);
175 cvAddWeighted( img, g_alpha, skullResize, 1.0 - g_alpha, 0.0, img);
176 /* This is a part
177 cvCopy(skullResize, img); */
178 cvResetImageROI(img);
179 cvReleaseImage(&skullResize);
180
181 // cvRectangle(img, cvPoint(r->x*scale,r->y*scale), cvPoint((r->x+r->width)*scale,(r->y+r->height)*scale), colors[i%8]);
182 }
183 /* for( int i = 0; i < (objects? objects->total : 0); i++ )
184 {
185 CvRect* r = (CvRect*)cvGetSeqElem( objects, i );
186 CvPoint center;
187 int radius;
188 center.x = cvRound((r->x + r->width*0.5)*scale);
189 center.y = cvRound((r->y + r->height*0.5)*scale);
190 radius = cvRound((r->width + r->height)*0.25*scale);
191 cvCircle( img, center, radius, colors[i%8], 3, 8, 0 );
192 } */
193
194 cvShowImage( WND_RESULT, img );
195 cvReleaseImage(&gray);
196 cvReleaseImage(&small_img);
197 }
运行结果（此时的alpha为0.2）：
