Question

我正在使用EmguCV 3.0.0包装器来使用OpenCV 3.0。 EmguCV PCACompute方法包装了OpenCV PCA::operator()方法。

以下代码编译并运行。评论应该很好地解释意图。

// Populate the 5 row by 8 column input array (5 samples of 8 dimensions).
// The sample dimensions (columns) vary like this:
//   - low variance: 0, 1, 4, 5, 6, 7
//   - high variance: 2, 3
Matrix<double> input = new Matrix<double>(5, 8);
var r = new Random();
for (int row = 0; row < 5; row++) {
    input.Data[row,0] = r.Next(0, 10);     // low variance
    input.Data[row,1] = r.Next(0, 20);     // low variance
    input.Data[row,2] = r.Next(80, 210);   // high variance
    input.Data[row,3] = r.Next(0, 240);    // highest variance
    input.Data[row,4] = r.Next(20, 21);    // very low variance
    input.Data[row,5] = r.Next(0, 10);     // low variance
    input.Data[row,6] = r.Next(0, 10);     // low variance
    input.Data[row,7] = r.Next(200, 210);  // low variance
}

// create output array for PCACompute()
var eigenvectors = new Matrix<double>(8, 8);

// create *empty* mean array so that PCACompute() calculates its own means
var means = new Mat();

// HERE IS THE MAGIC.
CvInvoke.PCACompute(input, means, eigenvectors);

但魔法被打破了。毕竟eigenvectors全是零。这个漂亮的打印代码：

// print each eigenvector on its own line
for (int vectorIdx = 0; vectorIdx < eigenvectors.Rows; vectorIdx++) {
    string vectorStr = "";
    for(int dimension = 0; dimension < eigenvectors.Cols; dimension++) {
        vectorStr += eigenvectors.Data[vectorIdx, dimension].ToString() + ", ";
    }
    Console.WriteLine("{ " + vectorStr.Substring(0, vectorStr.Length - 2) + " }");
}

给出了这个输出：

{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }
{ 0, 0, 0, 0, 0, 0, 0, 0 }

事实上，如果我在之前将eigenvectors 的成员设置为PCACompute：

eigenvectors.Data[1,1] = 42; CvInvoke.PCACompute(input, means, eigenvectors);

漂亮的图片显示 eigenvectors完全不受PCACompute影响：

{ 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 42, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 } { 0, 0, 0, 0, 0, 0, 0, 0 }

这是一个错误，还是我做错了？

PCACompute（）不会触及Matrix＆lt;＆gt;输出数组参数

0 个答案: