不是判断的是点（i,j）吗？
为什么写入的时候变成了(j,i)
那应该是如何理解，谢谢各位大牛

所有源码：
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/ml/ml.hpp>
using namespace cv;
int main()
{
// Data for visual representation
int width = 512, height = 512;
Mat image = Mat::zeros(height, width, CV_8UC3);
// Set up training data
float labels[5] = {1.0, -1.0, -1.0, -1.0,1.0};
Mat labelsMat(5, 1, CV_32FC1, labels);
float trainingData[5][2] = { {501, 10}, {255, 10}, {501, 255}, {10, 501},{501,128} };
Mat trainingDataMat(5, 2, CV_32FC1, trainingData);
//设置支持向量机的参数
CvSVMParams params;
params.svm_type = CvSVM::C_SVC;//SVM类型：使用C支持向量机
params.kernel_type = CvSVM::LINEAR;//核函数类型：线性
params.term_crit = cvTermCriteria(CV_TERMCRIT_ITER, 100, 1e-6);//终止准则函数：当迭代次数达到最大值时终止
//训练SVM
//建立一个SVM类的实例
CvSVM SVM;
//训练模型，参数为：输入数据、响应、XX、XX、参数（前面设置过）
SVM.train(trainingDataMat, labelsMat, Mat(), Mat(), params);
Vec3b green(0,255,0), blue (255,0,0);
//显示判决域
for (int i = 0; i < image.rows; ++i)
for (int j = 0; j < image.cols; ++j)
{
Mat sampleMat = (Mat_<float>(1,2) << i,j);
//predict是用来预测的，参数为：样本、返回值类型（如果值为ture而且是一个2类问题则返回判决函数值，否则返回类标签）、
float response = SVM.predict(sampleMat);
if (response == 1)
image.at<Vec3b>(j, i) = green;
else if (response == -1)
image.at<Vec3b>(j, i) = blue;
}
//画出训练数据
int thickness = -1;
int lineType = 8;
circle( image, Point(501, 10), 5, Scalar( 0, 0, 0), thickness, lineType);//画圆
circle( image, Point(255, 10), 5, Scalar(255, 255, 255), thickness, lineType);
circle( image, Point(501, 255), 5, Scalar(255, 255, 255), thickness, lineType);
circle( image, Point( 10, 501), 5, Scalar(255, 255, 255), thickness, lineType);
circle(image, Point( 501, 128), 5, Scalar(0, 0, 0), thickness, lineType);
//显示支持向量
thickness = 2;
lineType = 8;
//获取支持向量的个数
int c = SVM.get_support_vector_count();
for (int i = 0; i < c; ++i)
{
//获取第i个支持向量
const float* v = SVM.get_support_vector(i);
//支持向量用到的样本点，用灰色进行标注
circle( image, Point( (int) v[0], (int) v[1]), 6, Scalar(128, 128, 128), thickness, lineType);
}
imwrite("result.png", image); // save the image
imshow("SVM Simple Example", image); // show it to the user
waitKey(0);
}

你知道图像坐标系怎么建的吗？然后看看rows 和cols 代表y和x