C和opencv实现图像显示图像的蓝色的直方图，使用IplImage

以下是使用C和OpenCV实现图像显示图像的蓝色直方图的示例代码：

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

int main(int argc, char** argv)
{
    // 读取图像
    IplImage* img = cvLoadImage(argv[1], CV_LOAD_IMAGE_COLOR);

    // 分离通道
    IplImage* blue = cvCreateImage(cvGetSize(img), IPL_DEPTH_8U, 1);
    cvSplit(img, blue, NULL, NULL, NULL);

    // 计算直方图
    CvHistogram* hist;
    int hist_size = 256;
    float range[] = {0, 256};
    float* ranges[] = {range};
    hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, ranges, 1);
    cvCalcHist(&blue, hist, 0, NULL);

    // 获取最大值
    float max_value = 0;
    cvGetMinMaxHistValue(hist, NULL, &max_value, NULL, NULL);

    // 创建画布
    int width = 512, height = 400;
    IplImage* canvas = cvCreateImage(cvSize(width, height), IPL_DEPTH_8U, 3);
    cvZero(canvas);

    // 绘制直方图
    int bin_width = cvRound((double) width / hist_size);
    for (int i = 0; i < hist_size; i++) {
        float bin_value = cvGetReal1D(hist->bins, i);
        int intensity = cvRound(bin_value * height / max_value);
        cvRectangle(canvas, cvPoint(i * bin_width, height), cvPoint((i + 1) * bin_width, height - intensity), CV_RGB(0, 0, 255), -1);
    }

    // 显示图像和直方图
    cvNamedWindow("Image", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("Histogram", CV_WINDOW_NORMAL);
    cvShowImage("Image", img);
    cvShowImage("Histogram", canvas);
    cvWaitKey(0);

    // 释放内存
    cvReleaseImage(&img);
    cvReleaseImage(&blue);
    cvReleaseImage(&canvas);
    cvReleaseHist(&hist);
    cvDestroyAllWindows();

    return 0;
}

该代码会读取一张图像，将其蓝色通道分离出来，计算蓝色直方图，并在窗口中显示原始图像和蓝色直方图。请注意，该示例代码使用的是IplImage而不是Mat。如果使用Mat，代码会有所不同。