OpenCV 像素加入雜訊－天天向上

之前有寫過一篇關於OpenCV像素取/存值的方式[1]

彩色像素取值

image.at<cv::Vec3b>(row, col)[0]

image.at<cv::Vec3b>(row, col)[1]

image.at<cv::Vec3b>(row, col)[2]

灰階像素取值

image.at<uchar>(row, col) = 255;

加上另一篇[2] 利用C# 拉UI並傳參數給OpenCV C++ DLL

規劃如下:

C# 公開函數:

UI只需要傳入雜訊點數(numPts),

對使用者來說並不需要知道用哪一個Mat影像資料(這部分由C++實作)

C++私有函數:

針對圖像資料(image), 加入指定的雜訊點數(numPts),

該點數則C#公開函數傳來

宣告imageProcLib.hpp

實作imageProcLib.cpp

//----------------------------------------------------------------void ImageProc::AddNoise(int numPts){    imgDst = img.clone();    AddNoise(imgDst, numPts);}void ImageProc::AddNoise(Mat image, int numPts){    int i, row, col;    if(image.channels() == 3)    // 彩色    {        for(i=0; i<numPts; i++)        {            row = rand() % image.rows;            col = rand() % image.cols;            image.at<cv::Vec3b>(row, col)[0] = 255;            image.at<cv::Vec3b>(row, col)[1] = 255;            image.at<cv::Vec3b>(row, col)[2] = 255;        }    }else                       // 灰階     {        for(i=0; i<numPts; i++)        {            row = rand() % image.rows;            col = rand() % image.cols;            image.at<uchar>(row, col) = 255;        }    }}//----------------------------------------------------------------

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C# GUI如下

為了怕使用者未先載入圖像所以加入讀取檔案是否成功

imageProcLib.hpp

bool ImageProc::IsImgLoaded();                  // 檢查讀取檔案是否成功

imageProcLib.cpp

bool ImageProc::IsImgLoaded()                          // 檢查讀取檔案是否成功{    return (!img.data);}

C# UI選取一張照片, 然後傳入雜訊點數並顯示結果影像

private void openToolStripMenuItem_Click(object sender, EventArgs e)      {          using (OpenFileDialog ofd = new OpenFileDialog())          {              if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)              {                  unsafe                  {                      fixed (char* filename = ofd.FileName)                      {                          imgProc.imread(filename);                          int numPts = Convert.ToInt16(numericUpDown1.Value);                          if (!imgProc.IsImgLoaded())              // 檢查讀取檔案是否成功                          {                              imgProc.AddNoise(numPts);            // 加入雜訊點數                              imgProc.showImage();                 // 顯示影像                          }                      }                  }               }          }      }       // 動態更新      private void numericUpDown1_ValueChanged(object sender, EventArgs e)      {             int numPts = Convert.ToInt16(numericUpDown1.Value);             try             {                 if (!imgProc.IsImgLoaded())           // 檢查讀取檔案是否成功                 {                     imgProc.AddNoise(numPts);         // 加入雜訊點數                     imgProc.showImage();              // 顯示影像                 }                 else                 {                     MessageBox.Show("請先載入一張照片");                 }             }             catch (Exception ex)             {                 MessageBox.Show(ex.Message);             }              }

測試如下

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接下來, 練習[3] normally distributed random numbers (randn)

以下為原發問者問題描述節錄:

here's my problem: I'm trying to create a simple program which adds Gaussian noise to an input image. The only constraints are that the input image is of type CV_64F (i.e. double) and the values are and must be kept normalized between 0 and 1.

The code I wrote is the following:

Mat my_noise;
my_ noise = Mat (input.size(), input.type());

randn(noise, 0, 5); //mean and variance

input += noise;

The above code doesn't work, the resulting image doesn't get displayed properly. I think that happens because it gets out of the 0,1 range. I modified the code like this:

Mat my_noise;
my_ noise = Mat (input.size(), input.type());

randn(noise, 0, 5); //mean and variance

input += noise;

normalize(input, input, 0.0, 1.0, CV_MINMAX, CV_64F);

but it still doesn't work. Again, the resulting image doesn't get displayed properly. Where is the problem? Remember: the input image is of type CV_64F and the values are normalized between 0 and 1 before adding noise and have to remain like also after the noise addition.

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imageProcLib.hpp

void AddNoiseRandN();                           // 加入 normally distributed random numbersvoid AddNoiseRandN(double mean, double std);

imageProcLib.cpp

//----------------------------------------------------------------void ImageProc::AddNoiseRandN(double mean, double stddev){    if(img.channels() == 3)    {        vector<Mat> spl;        split(img, spl);        noise = Mat(spl[0].size(), CV_64F);        randn(noise, mean, stddev);                for(int i=0; i<3; i++)        {            normalize(spl[i], spl[i], 0.0, 1.0, CV_MINMAX, CV_64F);            spl[i] = spl[i] + noise;                                }        merge(spl, imgDst);     }}void ImageProc::AddNoiseRandN()                        // 加入 normally distributed random numbers{    AddNoiseRandN(0.0, 0.01); }

C# UI

private void randNToolStripMenuItem_Click(object sender, EventArgs e){    double mean = Convert.ToDouble(textBox1.Text);    double stddev = Convert.ToDouble(textBox2.Text);    using (OpenFileDialog ofd = new OpenFileDialog())    {        if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)        {            unsafe            {                fixed (char* filename = ofd.FileName)                {                    imgProc.imread(filename);                    if (!imgProc.IsImgLoaded())              // 檢查讀取檔案是否成功                    {                        imgProc.AddNoiseRandN(mean, stddev);                        imgProc.showImage();                 // 顯示影像                    }                }            }         }    }}