庞峰Opencv学习(三)--灰度直方图

  灰度直方图是一个帮助分析图像很有力的工具吧，今天学习了下，一天不敲代码就生疏啊- -

  灰度直方图这个程序主要有几个函数和结构体先说一下：

  1.  CreateHIst

         CvHistogram* cvCreateHist( int dims, int* sizes, int type,  float** ranges=NULL, int uniform=1 );

          dims代表直方图是几维的，本程序是一个一维直方图，即bins只由x坐标索引

         sizes 代表有多少个bins

         type有两种类型一是稠密数组CV_HIST_ARRAY和稀疏数组CV_HIST_TREE，这里由于是一维直方图我们选择稠密数组

         ranges代表了bins中值得取值范围，这里我们的灰度值为0-255，所以选取0-255

         uniform归一化标识，默认为1，标识x方向被等分为sizes个bins

  2. CalcHist

        void cvCalcHist( IplImage** image, CvHistogram* hist, int accumulate=0, const CvArr* mask=NULL );

       image为输入图像s

       hist为直方图指针

      这里需要注意如果要计算的图像是多通道时，可以用多个单通道图来表示

    

#include "cv.h"#include "cxcore.h"#include "highgui.h"#include <stdio.h>IplImage* DisplayHist(CvHistogram* hist, float xscalar=1, float yscalar =1){float maxHist=0;cvGetMinMaxHistValue(hist, 0, &maxHist , 0 ,0);IplImage* histimg = cvCreateImage(cvSize(256*xscalar,64*yscalar),8 ,1);cvZero(histimg);//取出直方图中的灰度值，并进行归一化处理float currentVal=0;float nextVal=0;for (int i=0; i<255;i++){currentVal = cvQueryHistValue_1D(hist,i);nextVal = cvQueryHistValue_1D(hist,i+1);CvPoint pt[4];pt[1] = cvPoint(i*xscalar, 64*yscalar);pt[2] = cvPoint((i+1)*xscalar, 64*yscalar);pt[3] = cvPoint((i+1)*xscalar, (64-(nextVal/maxHist)*64)*yscalar);pt[4] = cvPoint(i*xscalar, (64-(currentVal/maxHist)*64)*yscalar);//填充凸多边形int npts = 5;CvPoint pts[5];pts[0]=pt[1];pts[1]=pt[2];pts[2]=pt[3];pts[3]=pt[4];pts[4]=pt[1];cvFillConvexPoly(histimg,pts,npts,cvScalar(255));//白色填充}return histimg;}void main(){IplImage* src = cvLoadImage("lena.jpg");cvNamedWindow("src");cvShowImage("src",src);CvHistogram* hist;int sizes = 256;//有256个binsint dims = 1;//一维直方图float range[] = {0,255}; //灰度图深度0-255float* ranges[] = {range};hist = cvCreateHist(dims, &sizes, CV_HIST_ARRAY/*稠密数组*/,ranges,1);cvClearHist(hist);IplImage* bimg = cvCreateImage(cvGetSize(src), 8 , 1);IplImage* gimg = cvCreateImage(cvGetSize(src), 8 , 1);IplImage* rimg = cvCreateImage(cvGetSize(src), 8 , 1);cvSplit(src,bimg,gimg,rimg,NULL);cvCalcHist(&bimg,hist,0,0);IplImage *bhist = DisplayHist(hist);cvNamedWindow("b");cvShowImage("b",bhist);cvClearHist(hist);cvCalcHist(&gimg,hist,0,0);IplImage *ghist = DisplayHist(hist);cvNamedWindow("g");cvShowImage("g",ghist);cvClearHist(hist);cvCalcHist(&rimg,hist,0,0);IplImage *rhist = DisplayHist(hist);cvNamedWindow("r");cvShowImage("r",rhist);cvClearHist(hist);cvWaitKey(0);cvReleaseImage(&src);cvReleaseImage(&bimg);cvReleaseImage(&gimg);cvReleaseImage(&rimg);}