【OpenCV】直方图——一维

int main()
{
IplImage* src = cvLoadImage("J:\\baboon.jpg", CV_LOAD_IMAGE_COLOR);//加载原始图像，路径根据实际情况替换
IplImage* gray_plan = cvCreateImage(cvGetSize(src), IPL_DEPTH_8U, 1);//创建单通道的灰度图像对象
IplImage* b_plan = cvCreateImage(cvGetSize(src), 8, 1);//创建蓝色通道的图像对象
IplImage* g_plan = cvCreateImage(cvGetSize(src), 8, 1);//创建绿色通道的灰度图像对象
IplImage* r_plan = cvCreateImage(cvGetSize(src), 8, 1);//创建红色通道的灰度图像对象
IplImage* ept_plan = cvCreateImage(cvGetSize(src), 8, 1);//创建单通道的“空白”图像对象，用来合成RGB3通道图像对象
cvZero(ept_plan);//将图像所有通道所有元素都设置为0，否则在用cvMerge合并图像时，得到的结果不是“正色”。感兴趣可以自己cvShowImage ept_plan看看什么样子。
cvCvtColor(src, gray_plan, CV_BGR2GRAY);//将原始图像（BGR）转换成灰度图像

IplImage* bImg = cvCreateImage(cvGetSize(src), IPL_DEPTH_8U, 3);//创建3通道图像
IplImage* gImg = cvCreateImage(cvGetSize(src), 8, 3);
IplImage* rImg = cvCreateImage(cvGetSize(src), 8, 3);

cvSplit(src, b_plan, g_plan, r_plan, 0);//将原始图像分离成B、G、R 3个单通道的图像
cvMerge(b_plan, ept_plan, ept_plan, 0, bImg);//合并3通道蓝色图像
cvMerge(ept_plan, g_plan, ept_plan, 0, gImg);
cvMerge(ept_plan, ept_plan, r_plan, 0, rImg);
cvNamedWindow("B-Image", 1);
cvShowImage("B-Image", bImg);
cvNamedWindow("G-Image", 1);
cvShowImage("G-Image", gImg);
cvNamedWindow("R-Image", 1);
cvShowImage("R-Image", rImg);

int dims = 1;//直方图维数
int hist_size = 256;//直方图维数的长度
int hist_height = 256;//源图像尺寸 512*512

//灰度直方图
float range[] = {0, 255};//直方图中每个维数对应的取值范围，该值会影响直方图统计结果
float* ranges[] = { range };//数组的长度与维数相同
CvHistogram* gray_hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, ranges, 1);//创建直方图对象
cvCalcHist(&gray_plan, gray_hist, 0, 0);//计算图像直方图
cvNormalizeHist(gray_hist, 1.0);//归一化直方图元素
float max_value = 0;
cvGetMinMaxHistValue(gray_hist, 0, &max_value, 0, 0);//获取直方图中最大值

//蓝色直方图
float rangeB[] = {0, 255};
float* rangesB[] = {rangeB};
CvHistogram* b_hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, rangesB, 1);
cvCalcHist(&b_plan, b_hist, 0, 0);
cvNormalizeHist(b_hist, 1.0);
float max_value_b = 0;
cvGetMinMaxHistValue(b_hist, 0, &max_value_b, 0, 0);

//绿色直方图
float rangeG[] = { 0, 255 };
float* rangesG[] = { rangeG };
CvHistogram* g_hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, rangesG, 1);
cvCalcHist(&g_plan, g_hist, 0, 0);
cvNormalizeHist(g_hist, 1.0);
float max_value_g = 0;
cvGetMinMaxHistValue(g_hist, 0, &max_value_g, 0, 0);

//红色直方图
float rangeR[] = { 0, 255 };
float* rangesR[] = { rangeR };
CvHistogram* r_hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, rangesR, 1);
cvCalcHist(&r_plan, r_hist, 0, 0);
cvNormalizeHist(r_hist, 1.0);
float max_value_r = 0;
cvGetMinMaxHistValue(r_hist, 0, &max_value_r, 0, 0);

int scale = 2;//生成的直方图图像的比例向量
int split = 5;//灰度、蓝色、绿色、红色 四个类型直方图在直方图图像中的间隔像素
IplImage* hist_image = cvCreateImage(cvSize(hist_size * scale * 2 + split, hist_height * 2 + split), 8, 3);//创建直方图图像对象（在一张图里面显示四种直方图）
cvZero(hist_image);

for (int i = 0; i < hist_size; i++)//画灰度直方图
{
float bin_val = cvQueryHistValue_1D(gray_hist, i);
int intensity = cvRound(bin_val*hist_height / max_value);//要绘制的高度
cvRectangle(hist_image,//矩形画在直方图图像内
cvPoint(i*scale, hist_height),//矩形对角线中的一个点
cvPoint((i + 1) * scale - 1, hist_height - intensity),//矩形对角线中的另一个点
CV_RGB(255, 255, 255));
}

for (int i = 0; i < hist_size; i++)//画蓝色通道直方图
{
float bin_val = cvQueryHistValue_1D(b_hist, i);
int intensity = cvRound(bin_val * hist_height / max_value_b);
cvRectangle(hist_image,
cvPoint(i * scale + (split + hist_size * scale), hist_height),
cvPoint((i + 1) * scale - 1 + (split + hist_size * scale), hist_height - intensity),
CV_RGB(0, 0, 255));
}

for (int i = 0; i < hist_size; i++)//画绿色通道直方图
{
float bin_val = cvQueryHistValue_1D(g_hist, i);
int intensity = cvRound(bin_val * hist_height / max_value_g);
cvRectangle(hist_image,
cvPoint(i * scale + split, hist_height * 2 + split),
cvPoint((i + 1) * scale - 1 + split, hist_height * 2 + split - intensity),
CV_RGB(0, 255, 0));
}

for (int i = 0; i < hist_size; i++)//画红色通道直方图
{
float bin_val = cvQueryHistValue_1D(r_hist, i);
int intensity = cvRound(bin_val * hist_height / max_value_r);
cvRectangle(hist_image,
cvPoint(i * scale + (split + hist_size * scale), hist_height * 2 + split),
cvPoint((i + 1) * scale - 1 + (split + hist_size * scale), hist_height * 2 + split - intensity),
CV_RGB(255, 0, 0));
}

cvNamedWindow("Gray Source", 1);
cvNamedWindow("Histogram", 1);
cvShowImage("Gray Source", gray_plan);
cvShowImage("Histogram", hist_image);

cvWaitKey(0);

cvDestroyAllWindows();
cvReleaseImage(&gray_plan);
cvReleaseImage(&hist_image);
}