直方图（下）

// 直方图的RGB.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "opencv2/opencv.hpp"
#define cvQueryHistValue_1D( hist, idx0 ) \
    ((float)cvGetReal1D( (hist)->bins, (idx0)))


IplImage* DrawHistogram(CvHistogram* hist, int scaleX= 1, int scaleY= 1)
   {  
	   float histMax= 0;
	   cvGetMinMaxHistValue(hist, 0, &histMax, 0, 0);  //获取直方图的最大值
	   if(!histMax)
	   {
		   histMax= 1;
        }
	   IplImage* imgHist= cvCreateImage(cvSize(256* scaleX, 64* scaleY), 8, 1);
	   cvZero(imgHist);     //置零

	   for(int i=0; i< 255; i++)
	   {
	        float histValue= cvQueryHistValue_1D(hist, i);   //获取第i个bin 的值
			float nextValue= cvQueryHistValue_1D(hist, i+1);

			CvPoint pt1= cvPoint((i+ 100)* scaleX, 64* scaleY);  //构建四个点
			CvPoint pt2= cvPoint((i+ 101)* scaleX, 64* scaleY);
			CvPoint pt3= cvPoint((i+101)* scaleX, (int )((1- nextValue/ histMax)* 64* scaleY));
			CvPoint pt4= cvPoint((i+ 100)* scaleX, (int)((1-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;

			cvFillConvexPoly(imgHist, pts, numPts, cvScalar(255));
	   }

	   return imgHist;
   }

int _tmain(int argc, _TCHAR* argv[])
{ 
	IplImage* src0= cvLoadImage("F://Opencv_picture\\05.jpg");
	IplImage* src= cvCreateImage(cvGetSize(src0), IPL_DEPTH_8U, 3);

	cvConvertScale(src0, src, 1.0, 0);
	cvNamedWindow("Histogram");

	cvShowImage("Histogram", src);
	int dims= 1; //直方图的维度、
	int sizes = 256; //直方图数据个数
	float range[]= {0, 255}; //直方图每个维度取值范围
	float * ranges[]= {range};
	CvHistogram* hist;
	hist= cvCreateHist(dims, &sizes, CV_HIST_ARRAY, ranges, 1);

	cvClearHist(hist);
	IplImage* b_img= cvCreateImage(cvGetSize(src), 8, 1);
	IplImage* g_img= cvCreateImage(cvGetSize(src), 8, 1);
	IplImage* r_img= cvCreateImage(cvGetSize(src), 8, 1);

	cvSplit(src, b_img, g_img, r_img, NULL);   //分解图像到三个图像的内存空间
	cvCalcHist(&b_img, hist, 0, 0);    // 统计一个通道的数据额到hist
	b_img= DrawHistogram(hist);
	cvClearHist(hist);

	cvCalcHist(&b_img, hist, 0, 0);
	 g_img= DrawHistogram(hist);
	cvClearHist(hist);

	cvCalcHist(&r_img, hist, 0, 0);
	r_img= DrawHistogram(hist);
	cvClearHist(hist);

	cvNamedWindow("B");
	cvNamedWindow("G");
	cvNamedWindow("R");

     cvShowImage("B", b_img);
	 cvShowImage("G", g_img);
	 cvShowImage("R", r_img);

	 cvWaitKey(0);
	 cvReleaseImage(&src);
	 cvReleaseImage(&r_img);
	 cvReleaseImage(&b_img);
      cvReleaseImage(&g_img);

	  cvDestroyWindow("Histogram");
	  cvDestroyWindow("B");
	  cvDestroyWindow("G");
	  cvDestroyWindow("R");

	return 0;
}

FillConvexPoly
填充凸多边形

void cvFillConvexPoly( CvArr* img, CvPoint* pts, int npts,
CvScalar color, int line_type=8, int shift=0 );
img
图像。
pts
指向单个多边形的指针数组。
npts
多边形的顶点个数。
color
多边形的颜色。
line_type
组成多边形的线条的类型。参见cvLine
shift
顶点坐标的小数点位数。


函数cvFillConvexPoly填充凸多边形内部。这个函数比函数cvFillPoly 更快。它除了可以填充凸多边形区域还可以填充任何的单调多边形。例如：一个被水平线（扫描线）至多两次截断的多边形。