第11集 一维直方图
1.把彩***像分成3个图像(cvSplit)
2.创建直方图并且分配内存（CvHistogram* hist=cvCreateHist）
3.读取图像的直方图，把数据存放在直方图结构体中（cvCapcHist）
4.读取直方图结构体中每个值的点数（cvQueryHistValue_1D）
5.描点，画图（cvPoint，cvFillConvexPoly）
直方图的其它操作：
1.cvNorMalizeHist(CvHistogram* hist,double factor)
归一化直方图，factor表示直方图归一化后的数字
2.cvThreshHist(CvHistogram* hist,double factor);
factor是一个开关阀值，小于该阀值的各个bin的值都被设为0
3.void cvCopyHist(const CvHistogram* src,CvHistogram** dst);
复制一个直方图的信息到另一个直方图，如果设置*dst为NULL，那么生成一个与src一样大小的新直方图，*dst被分配给一个指向新分配的直方图的指针
4.cvGetMinMaxHistValue(const CvHistogram* hist,float* min_value,float* max_value,int min_idx=NULL,int max_idx=NULL)
求直方图hist中的最小最大值及其索引
5.cvCalcHist(IplImage** image,CvHistogram* hist,int accumulate=0,const CvArr* mask=NULL);
从图像中自动计算直方图，图像要转换为单通道图像，accumulate如果非零，表示直方图hist在读入图像之前没有被清零，允许cvCalcHist()在一个数据采集循环中被多次调用，mask如果非零，则只有与mask非零元素对应
6.double cvCompareHist(const CvHistogram* hist1,const CvHistogram* hist2,int method)
比较两个大小相同的直方图的相似度
程序1（自己）：
#include "cv.h"
#include "cxcore.h"
#include "highgui.h"
IplImage* cvDrawHist(IplImage *image,int x=1,int y=1)
{
int dim=1;
int size=256;
float range[]={0,255};
float *ranges[]={range}; //数组的个数等于维数，这里是一维
CvHistogram *hist=cvCreateHist(dim,&size,CV_HIST_ARRAY,ranges,1);
cvClearHist(hist);
cvCalcHist(&image,hist);
float max=0;
cvGetMinMaxHistValue(hist,NULL,&max);
IplImage *HistImage=cvCreateImage(cvSize(256*x,64*y),8,1);
cvZero(HistImage);
CvPoint pts[5];
for(int i=0;i<255;i++)
{
float num=cvQueryHistValue_1D(hist,i);
float nextnum=cvQueryHistValue_1D(hist,i+1);
pts[0]=cvPoint(i*x,0);
pts[1]=cvPoint((i+1)*x,0);
pts[2]=cvPoint((i+1)*x,64*y-nextnum/max*64*y);
pts[3]=cvPoint(i*x,64*y-num/max*64*y);
pts[4]=cvPoint(i*x,0);
cvFillConvexPoly(HistImage,pts,5,cvScalar(255));
}
return HistImage;
}
void main()
{
IplImage *src=cvLoadImage("c:\\1.jpg");
cvNamedWindow("src");
cvShowImage("src",src);
IplImage *red=cvCreateImage(cvGetSize(src),8,1);
IplImage *green=cvCreateImage(cvGetSize(src),8,1);
IplImage *blue=cvCreateImage(cvGetSize(src),8,1);
cvSplit(src,red,green,blue,NULL);
cvNamedWindow("red");
cvNamedWindow("green");
cvNamedWindow("blue");
cvShowImage("red",red);
cvShowImage("green",green);
cvShowImage("blue",blue);
IplImage *r_hist=cvDrawHist(red);
IplImage *b_hist=cvDrawHist(blue);
IplImage *g_hist=cvDrawHist(blue);
cvNamedWindow("r_hist");
cvNamedWindow("g_hist");
cvNamedWindow("b_hist");
cvShowImage("r_hist",r_hist);
cvShowImage("g_hist",b_hist);
cvShowImage("b_hist",g_hist);
cvWaitKey(0);
cvDestroyWindow("red");
cvReleaseImage(&red);
cvDestroyWindow("green");
cvReleaseImage(&green);
cvDestroyWindow("blue");
cvReleaseImage(&blue);
cvDestroyWindow("r_hist");
cvReleaseImage(&r_hist);
cvDestroyWindow("g_hist");
cvReleaseImage(&g_hist);
cvDestroyWindow("b_hist");
cvReleaseImage(&b_hist);
}
程序2：
#include "cv.h"
#include "cxcore.h"
#include "highgui.h"
//绘制直方图
IplImage* DrawHistogram(CvHistogram* hist , float scaleX = 1 , float scaleY = 1)
{
//获取直方图中极大值
float histMax = 0;
cvGetMinMaxHistValue(hist , 0 ,&histMax ,0 ,0);
//创建图像 该图像用于显示直方图
IplImage* imgHist = cvCreateImage(cvSize(256*scaleX , 64*scaleY) , 8 ,1);
//图像置零
cvZero(imgHist);
//依次绘制直方图的bin
for(int i=0;i<255;i++)
{
//获取直方图的值
float histValue = cvQueryHistValue_1D(hist , i);
float nextValue = cvQueryHistValue_1D(hist , i+1);
//获取四边形的四个点的坐标 详情请观看视频的讲解
CvPoint pt1 = cvPoint( i*scaleX , 64*scaleY);
CvPoint pt2 = cvPoint( (i+1)*scaleX , 64*scaleY);
CvPoint pt3 = cvPoint( (i+1)*scaleX , (64 - (nextValue/histMax)*64) *scaleY );
CvPoint pt4 = cvPoint ( i*scaleX , (64 - (histValue/histMax)*64) *scaleY );
int numPts = 5;
CvPoint pts[5];
pts[0] = pt1;
pts[1] = pt2;
pts[2] = pt3;
pts[3] = pt4;
pts[4] = pt1;
//填充四边形
cvFillConvexPoly(imgHist , pts ,numPts , cvScalar(255));
}
return imgHist;
}
int main(int argc, char* argv[])
{
//加载图像
IplImage* src = cvLoadImage("c:\\1.jpg");
cvNamedWindow("sr");
cvShowImage("sr" , src);
int dims = 1; // 一维直方图
int size =256; //bin的个数
float range[] = {0,255}; //取值范围
float* ranges[] = {range};
CvHistogram* hist;
//创建直方图
hist = cvCreateHist(dims , &size , CV_HIST_ARRAY , ranges , 1 );
//清空直方图
cvClearHist(hist);
//给B G R 三个通道的图像分配空间
IplImage* imgRed = cvCreateImage(cvGetSize(src) , 8 ,1);
IplImage* imgGreen = cvCreateImage(cvGetSize(src) , 8 ,1);
IplImage* imgBlue = cvCreateImage(cvGetSize(src) , 8 ,1);
//将图像src 分解成B G R 三个通道
cvSplit(src , imgBlue , imgGreen , imgRed , NULL);
//计算B通道 直方图
cvCalcHist(&imgBlue , hist , 0 , 0 );
//绘制B通道直方图 结果保存在histBlue
IplImage* histBlue = DrawHistogram(hist);
//将B通道的直方图数据清空
cvClearHist(hist);
//计算G通道直方图
cvCalcHist(&imgGreen , hist , 0 , 0 );
//绘制G通道直方图 histGreen
IplImage* histGreen = DrawHistogram(hist);
//将G通道的直方图数据清空
cvClearHist(hist);
//计算R通道 直方图
cvCalcHist(&imgRed , hist , 0 , 0 );
//绘制R通道直方图 histRed
IplImage* histRed = DrawHistogram(hist);
//将R通道的直方图数据清空
cvClearHist(hist);
cvNamedWindow("B");
cvNamedWindow("G");
cvNamedWindow("R");
cvShowImage("B" , histBlue);
cvShowImage("G" , histGreen);
cvShowImage("R" , histRed);
cvWaitKey(0);
//释放资源
//(1) 释放源图像
cvReleaseImage(&src);
//(2) 释放三个通道的图像
cvReleaseImage(&imgRed);
cvReleaseImage(&imgGreen);
cvReleaseImage(&imgBlue);
//(3)释放三个通道直方图
cvReleaseImage(&histBlue);
cvReleaseImage(&histGreen);
cvReleaseImage(&histRed);
//(4)释放直方图空间
cvReleaseHist(&hist);
return 0;
}