利用OpenCV的人脸检测给头像带上圣诞帽

原图：

效果：

    原理其实很简单：

采用一张圣诞帽的png图像作为素材，

    利用png图像背景是透明的，贴在背景图片上就是戴帽子的效果了。

人脸检测的目的主要是为了确定贴帽子的位置，类似ps中自由变换的功能，检测到人脸中间的位置，resize圣诞帽子和人脸大小匹配，确定位置，贴上去，ok！

代码：非常简洁，根据参考博客给出的代码，由OpenCV自带的人脸检测代码经过简单修改即可。

// getheader.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"

#include <iostream>
#include <stdio.h>

using namespace std;
using namespace cv;


#pragma comment(lib,"opencv_core2410d.lib")                
#pragma comment(lib,"opencv_highgui2410d.lib")                
//#pragma comment(lib,"opencv_objdetect2410d.lib")   
#pragma comment(lib,"opencv_imgproc2410d.lib")  

/** Function Headers */
void detectAndDisplay( Mat frame );

/** Global variables */
//-- Note, either copy these two files from opencv/data/haarscascades to your current folder, or change these locations
String face_cascade_name = "D:\\Program Files\\opencv\\sources\\data\\haarcascades\\haarcascade_frontalface_alt.xml";
String eyes_cascade_name = "D:\\Program Files\\opencv\\sources\\data\\haarcascades\\haarcascade_eye_tree_eyeglasses.xml";
CascadeClassifier face_cascade;
CascadeClassifier eyes_cascade;
string window_name = "Capture - Face detection";
RNG rng(12345);

const int FRAME_WIDTH = 1280;
const int FRAME_HEIGHT = 240;
/**
* @function main
*/
int main( void )
{
	CvCapture* capture;
	//VideoCapture capture;
	Mat frame;

	//-- 1. Load the cascades
	if( !face_cascade.load( face_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };
	if( !eyes_cascade.load( eyes_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };

			frame = imread("19.jpg");//背景图片

			//-- 3. Apply the classifier to the frame
			if( !frame.empty() )
			{ detectAndDisplay( frame ); }
			
			waitKey(0);
	
	return 0;
}

void mapToMat(const cv::Mat &srcAlpha, cv::Mat &dest, int x, int y)
{
	int nc = 3;
	int alpha = 0;

	for (int j = 0; j < srcAlpha.rows; j++)
	{
		for (int i = 0; i < srcAlpha.cols*3; i += 3)
		{
			alpha = srcAlpha.ptr<uchar>(j)[i / 3*4 + 3];
			//alpha = 255-alpha;
			if(alpha != 0) //4通道图像的alpha判断
			{
				for (int k = 0; k < 3; k++)
				{
					// if (src1.ptr<uchar>(j)[i / nc*nc + k] != 0)
					if( (j+y < dest.rows) && (j+y>=0) &&
						((i+x*3) / 3*3 + k < dest.cols*3) && ((i+x*3) / 3*3 + k >= 0) &&
						(i/nc*4 + k < srcAlpha.cols*4) && (i/nc*4 + k >=0) )
					{
						dest.ptr<uchar>(j+y)[(i+x*nc) / nc*nc + k] = srcAlpha.ptr<uchar>(j)[(i) / nc*4 + k];
					}
				}
			}
		}
	}
}

/**
* @function detectAndDisplay
*/
void detectAndDisplay( Mat frame )
{
	std::vector<Rect> faces;
	Mat frame_gray;
	Mat hatAlpha;

	hatAlpha = imread("2.png",-1);//圣诞帽的图片

	cvtColor( frame, frame_gray, COLOR_BGR2GRAY );
	equalizeHist( frame_gray, frame_gray );
	//-- Detect faces
	face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE, Size(30, 30) );

	for( size_t i = 0; i < faces.size(); i++ )
	{

		Point center( faces[i].x + faces[i].width/2, faces[i].y + faces[i].height/2 );
		// ellipse( frame, center, Size( faces[i].width/2, faces[i].height/2), 0, 0, 360, Scalar( 255, 0, 255 ), 2, 8, 0 );

		// line(frame,Point(faces[i].x,faces[i].y),center,Scalar(255,0,0),5);

		Mat faceROI = frame_gray( faces[i] );
		std::vector<Rect> eyes;

		//-- In each face, detect eyes
		eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CV_HAAR_SCALE_IMAGE, Size(30, 30) );

		for( size_t j = 0; j < eyes.size(); j++ )
		{
			Point eye_center( faces[i].x + eyes[j].x + eyes[j].width/2, faces[i].y + eyes[j].y + eyes[j].height/2 );
			int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
			// circle( frame, eye_center, radius, Scalar( 255, 0, 0 ), 3, 8, 0 );
		}

		// if(eyes.size())
		{
			resize(hatAlpha,hatAlpha,Size(faces[i].width, faces[i].height),0,0,INTER_LANCZOS4);
			// mapToMat(hatAlpha,frame,center.x+2.5*faces[i].width,center.y-1.3*faces[i].height);
			mapToMat(hatAlpha,frame,faces[i].x,faces[i].y-0.8*faces[i].height);
		}
	}
	//-- Show what you got
	imshow( window_name, frame );
	imwrite("merry christmas.jpg",frame);
}

参考文献：

http://blog.csdn.net/lonelyrains/article/details/50388999

http://docs.opencv.org/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html