C和opencv实现图像显示图像的紫色的直方图，使用IplImage

以下是使用C和OpenCV实现图像显示图像紫色直方图的示例代码，使用IplImage结构体：

#include <stdio.h>
#include <stdlib.h>
#include <cv.h>
#include <highgui.h>

int main(int argc, char** argv)
{
    // Load image
    IplImage* img = cvLoadImage(argv[1], CV_LOAD_IMAGE_UNCHANGED);
    if (!img)
    {
        printf("Error loading image\n");
        return -1;
    }

    // Create grayscale image
    IplImage* gray = cvCreateImage(cvGetSize(img), IPL_DEPTH_8U, 1);
    cvCvtColor(img, gray, CV_BGR2GRAY);

    // Create histogram
    int histSize = 256;
    float range[] = { 0, 256 };
    float* ranges[] = { range };
    CvHistogram* hist = cvCreateHist(1, &histSize, CV_HIST_ARRAY, ranges, 1);

    // Calculate histogram
    cvCalcHist(&gray, hist, 0, 0);

    // Find bin for purple color
    int purpleBin = cvRound(cvQueryHistValue_1D(hist, 140)); // Purple color range: 120-160

    // Display histogram
    int histWidth = 512;
    int histHeight = 400;
    int binWidth = cvRound((double)histWidth / histSize);
    IplImage* histImg = cvCreateImage(cvSize(histWidth, histHeight), 8, 3);
    cvZero(histImg);
    for (int i = 0; i < histSize; i++)
    {
        int binValue = cvRound(cvGetReal1D(hist->bins, i));
        CvScalar color;
        if (i == purpleBin)
            color = CV_RGB(255, 0, 255); // Purple bin
        else
            color = CV_RGB(255, 255, 255); // Other bins
        cvRectangle(histImg, cvPoint(i*binWidth, histHeight), cvPoint((i+1)*binWidth, histHeight - binValue/10), color, -1, 8, 0);
    }
    cvNamedWindow("Histogram", CV_WINDOW_AUTOSIZE);
    cvShowImage("Histogram", histImg);

    // Display image
    cvNamedWindow("Image", CV_WINDOW_AUTOSIZE);
    cvShowImage("Image", img);

    cvWaitKey(0);

    // Release resources
    cvReleaseImage(&img);
    cvReleaseImage(&gray);
    cvReleaseImage(&histImg);
    cvReleaseHist(&hist);

    return 0;
}

该程序首先加载图像，然后创建灰度图像，并使用OpenCV的cvCalcHist函数计算直方图。然后找到紫色直方图的bin，并创建一个新的IplImage对象，用于显示直方图。在该图像中，紫色的直方图bin被突出显示。最后，程序显示原始图像和直方图，并等待用户按下任意键以退出。