【练习4.3】在图片上画矩形并高亮显示矩形区域、统计矩形区域中像素情况并绘制直方图

《学习OpenCV》中文版第4章第3题

题目要求

程序代码

结果图片

题目要求：

①允许用户在图片上选择一个矩形区域，当鼠标放开，高亮显示矩形区域

②在另一个独立窗口中，使用绘图函数绘制一个图表，分别用蓝、绿和红色表示选中区域中各种颜色的像素在指定数值范围内的数量。

程序代码：

#include "stdafx.h"
#include <cv.h>
#include <highgui.h>
using namespace std;
using namespace cv;

//函数声明-->--->-->--->-->--->-->--->//

void MouseCallBack(int event, int x, int y, int flags, void *param);
void HighLight(IplImage * img, CvRect *rect);
void DrawHistogram(IplImage * colorImage, CvRect *rect, IplImage * imgHistogram);
int RangeCalculate(int value);

//<--<--<--<--<--<--<--<--<--函数声明//

CvRect box;
bool drawingBox = false;

void DrawBox(IplImage *img, CvRect rect)
{
    cvRectangle(img, cvPoint(rect.x, rect.y), cvPoint(rect.x + rect.width, rect.y + rect.height), cvScalar(255, 0, 0));
}

int _tmain(int argc, _TCHAR* argv[])
{
    box = cvRect(-1, -1, 0, 0);

    const char * fileName = "D:\Work\Work_Programming\Source\Image\introduction.jpg";
    IplImage * img = cvLoadImage(fileName, CV_LOAD_IMAGE_UNCHANGED);
    IplImage *drawHistogram = cvCreateImage(cvSize(240, img->width*img->height), IPL_DEPTH_8U, 3);

    cvNamedWindow("ExerciseWindow", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("区域直方图", 0);
    
    assert(img && drawHistogram);

    cvSetZero(drawHistogram);
    drawHistogram->origin = IPL_ORIGIN_BL;    //将图片原点设置为左下角

    IplImage * temp=cvCloneImage(img);
    IplImage * tempHist = cvCloneImage(drawHistogram);
    cvSetMouseCallback("ExerciseWindow", MouseCallBack, temp);
    
    while (true)
    {
        if (drawingBox)
        {
            cvCopyImage(img, temp);
            DrawBox(temp, box);

            cvCopyImage(drawHistogram, tempHist);
            DrawHistogram(img, &box, tempHist);
        }

        cvShowImage("ExerciseWindow", temp);
        cvShowImage("区域直方图", tempHist);

        if (waitKey(15) == 27)
        {
            break;
        }
    }

    cvWaitKey(0);

    cvReleaseImage(&img);
    cvReleaseImage(&drawHistogram);
    cvReleaseImage(&temp);
    cvReleaseImage(&tempHist);
    cvDestroyWindow("区域直方图");
    cvDestroyWindow("ExerciseWindow");     

    return 0;
}

//鼠标事件回调函数
void MouseCallBack(int event, int x, int y, int flags, void *param)
{
    IplImage * img = (IplImage *)param;
 
    switch (event)
    {
    case CV_EVENT_LBUTTONDOWN:
    {         
        drawingBox = true;
        box = cvRect(x, y, 0, 0);
    }
        break;
    case CV_EVENT_MOUSEMOVE:
    {     
        if (drawingBox)
        {
            box.width = x - box.x;
            box.height = y - box.y;
        }
    }
        break;
    case CV_EVENT_LBUTTONUP:
    {    
        drawingBox = false;
        if (box.width < 0)
        {
            box.x += box.width;
            box.width *= -1;
        }
        if (box.height < 0)
        {
            box.y += box.height;
            box.height *= -1;
        }
        HighLight(img, &box);
    }
        break;
    default:
        break;
    }      
}

//高亮显示矩形区域
void HighLight(IplImage * img, CvRect *rect)
{
    int startX = rect->x;
    int startY = rect->y;
    int boxWidth = rect->width;
    int boxHeight = rect->height;

    for (int h = startY; h < (startY+boxHeight); ++h)
    {
        uchar *ptr = (uchar *)(img->imageData + h*img->widthStep);    
        for (int w = startX; w < (startX+boxWidth); ++w)
        {
            ptr[3 * w + 2] = 255;
        }
    }
}

//统计矩形区域内像素情况并绘制直方图
void DrawHistogram(IplImage * colorImage,CvRect *rect,IplImage * imgHistogram)
{
    int arrCountB[8];    //存储B通道值在0-31、32-63....223-255这八段各段像素的个数
    int arrCountG[8];
    int arrCountR[8];

    for (int i = 0; i < 8; ++i)
    {
        arrCountB[i] = 0;
        arrCountG[i] = 0;
        arrCountR[i] = 0;
    }

    int startX = rect->x;
    int startY = rect->y;
    int boxWidth = rect->width;
    int boxHeight = rect->height;

    for (int h = startY; h < (startY + boxHeight); ++h)
    {
        uchar *ptr = (uchar *)(colorImage->imageData + h*colorImage->widthStep);
        for (int w = startX; w < (startX + boxWidth); ++w)
        {
            int rangeB = RangeCalculate(ptr[3 * w + 0]);    //判断B通道的当前值在哪个范围内，就将对应的arrCountB数组元素加一
            arrCountB[rangeB]++;

            int rangeG = RangeCalculate(ptr[3 * w + 1]);
            arrCountG[rangeG]++;

            int rangeR = RangeCalculate(ptr[3 * w + 2]);
            arrCountR[rangeR]++;
        }
    }

    int histWidth = 10;

    //分别绘制八个区间B、G、R柱
    for (int i = 0; i < 8; ++i)
    {
        cvRectangleR(imgHistogram, cvRect(3 * histWidth*i, 0, histWidth, arrCountB[i]), cvScalar(255, 0, 0), CV_FILLED);
        cvRectangleR(imgHistogram, cvRect(3 * histWidth*i + histWidth, 0, histWidth, arrCountG[i]), cvScalar(0, 255, 0), CV_FILLED);
        cvRectangleR(imgHistogram, cvRect(3 * histWidth*i + 2*histWidth, 0, histWidth, arrCountR[i]), cvScalar(0, 0, 255), CV_FILLED);
    }    
}

//判断值所在的区域段
int RangeCalculate(int value)
{
    if (value >= 0 && value <= 31)
    {
        return 0;
    }

    if (value >= 32 && value <= 63)
    {
        return 1;
    }

    if (value >= 64 && value <= 95)
    {
        return 2;
    }

    if (value >= 96 && value <= 127)
    {
        return 3;
    }

    if (value >= 128 && value <= 159)
    {
        return 4;
    }

    if (value >= 160 && value <= 191)
    {
        return 5;
    }

    if (value >= 192 && value <= 223)
    {
        return 6;
    }

    if (value >= 224 && value <= 255)
    {
        return 7;
    }
}

结果图片：