Emgu CV: 基礎影像容器Mat－天天向上

專案名稱:MatStructureEx

using Emgu.CV;
using Emgu.CV.Structure;
using Emgu.CV.CvEnum;
using System.Runtime.InteropServices;
using System.Diagnostics;
using Emgu.CV.Util;

宣告

Image<Bgr, byte> img;

開啟一張圖檔

using (OpenFileDialog ofd = new OpenFileDialog())
           {
               if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
               {
                   img = new Image<Bgr, byte>(ofd.FileName);
                   imageBox1.Image = img;
               }
           }

======================================

img內每一點像素值儲存在Mat資料結構內:

宣告一個MCvMat資料格式: managed structure eqivalent to CvMat

MCvMat mImg = (MCvMat)Marshal.PtrToStructure(img.Ptr, typeof(MCvMat));
byte* ptr = (byte*)mImg.Data.ToPointer();

private void DispMCvMatInfo(Mat img, DataGridView dgv, int rows, int cols)
    {
        int i, j;
        unsafe
        {
        
            MCvMat mImg = (MCvMat)Marshal.PtrToStructure(img.Ptr, typeof(MCvMat));
            byte* ptr = (byte*)mImg.Data.ToPointer();
            byte Red, Green, Blue;
            for (i = 0; i < rows; i++)
            {
                for (j = 0; j < cols; j++)
                {
                    Blue = ptr[0];
                    ptr++;
                    Green = ptr[0];
                    ptr++;
                    Red = ptr[0];
                    dgv[j, i].Value = string.Format("({0},{1} = ({2},{3},{4})", i + 1, j + 1, Red, Green, Blue);
                    ptr++;
                }

            }
            
        }
    }

主程式呼叫DispMCvMatInfo(),

可以將像素顯示在dataGridView1元件上, 語法如下:

DispMCvMatInfo(img.Mat, dataGridView1, rows, cols);

===================================

利用Split()函式抽取R,G,B

可以宣告一個Mat陣列, 其中

Mat[] mat = img.Mat.Split();

mat[0]: blue channel

mat[1]: green channel

mat[2]: red channel

Mat[] mat = img.Mat.Split();

可以將像素R,G,B顯示在dataGridView1元件上, 語法如下:

DispRGBMatInfo(mat[2], mat[1], mat[0], dataGridView1, rows, cols);

private void DispRGBMatInfo(Mat RedMat, Mat GreenMat, Mat BlueMat, DataGridView dgv, int rows, int cols)
        {
            int i, j;
            unsafe
            {
                MCvMat MCvMatRed = (MCvMat)Marshal.PtrToStructure(RedMat.Ptr, typeof(MCvMat));
                MCvMat MCvMatGreen = (MCvMat)Marshal.PtrToStructure(GreenMat.Ptr, typeof(MCvMat));
                MCvMat MCvMatBlue = (MCvMat)Marshal.PtrToStructure(BlueMat.Ptr, typeof(MCvMat));
                byte* pRed = (byte*)MCvMatRed.Data.ToPointer();
                byte* pGreen = (byte*)MCvMatGreen.Data.ToPointer();
                byte* pBlue = (byte*)MCvMatBlue.Data.ToPointer();
              
                byte red, green, blue;
                for (i = 0; i < rows; i++)
                {
                    for (j = 0; j < cols; j++)
                    {
                        red = pRed[0]; 
                        green = pGreen[0];
                        blue = pBlue[0]; 
                        pRed++;
                        pGreen++;
                        pBlue++;
                        dgv[j, i].Value = string.Format("({0},{1} = ({2},{3},{4})", i + 1, j + 1, red, green, blue);
                    }
                }
            }
        }

Split()可以用上面提到Mat陣列, 也可以用Image<Gray, byte>陣列去接收

Mat[] mat = img.Mat.Split();

改成

Image<Gray, byte>[] channels = img.Split();

imageBox2.Image = channels[2];
imageBox3.Image = channels[1];
imageBox4.Image = channels[0];

Red channel intensity

Blue channel intensity

Green channel intensity

如果要將R,G,B灰階強度改成對應紅色colormap,綠色colormap,藍色colormap顯示呢?

GetRedChannel();

GetGreenChannel();

GetBlueChannel();

以GetRedChannel為例,

1. 利用img.Split()先丟到channels

2. 將不感興趣的channel設定為零

3. 宣告一個VectorofMat資料型態, 可以輸入三個Gray level的資料,

即VectorofMat vm = new VectorofMat(channels[0].Mat, channels[1].Mat, channels[2].Mat)

其中0,1 channel已經被設定為0

private Image<Gray, byte>[] GetRedChannel()
       {
           // remove blue and green channels, ie. only red channel is saved
           int[] zeroCHs = new int[2] { 0, 1 };
           
           Image<Gray, byte>[] channels;
           Mat outMat = new Mat();
           channels = img.Split();    // img: original image(color)
           for(int i=0; i<2; i++)
               channels[ zeroCHs[i] ].SetZero();
           
           using (VectorOfMat vm = new VectorOfMat(channels[0].Mat, channels[1].Mat, channels[2].Mat))
           {
               CvInvoke.Merge(vm, outMat);
           }
           imageBox2.Image = outMat;
           return channels;
       }

private Image<Gray, byte>[] GetGreenChannel()
       {
           // remove blue and red channels, ie. only green channel is saved
           int[] zeroCHs = new int[2] { 0, 2 };

           Image<Gray, byte>[] channels;
           Mat outMat = new Mat();
           channels = img.Split();    // img: original image(color)
           for (int i = 0; i < 2; i++)
               channels[zeroCHs[i]].SetZero();

           using (VectorOfMat vm = new VectorOfMat(channels[0].Mat, channels[1].Mat, channels[2].Mat))
           {
               CvInvoke.Merge(vm, outMat);
           }
           imageBox3.Image = outMat;
           return channels;
       }

private Image<Gray, byte>[] GetBlueChannel()
       {
           // remove green and red channels, ie. only blue channel is saved
           int[] zeroCHs = new int[2] { 1, 2 };

           Image<Gray, byte>[] channels;
           Mat outMat = new Mat();
           channels = img.Split();    // img: original image(color)
           for (int i = 0; i < 2; i++)
               channels[zeroCHs[i]].SetZero();

           using (VectorOfMat vm = new VectorOfMat(channels[0].Mat, channels[1].Mat, channels[2].Mat))
           {
               CvInvoke.Merge(vm, outMat);
           }
           imageBox4.Image = outMat;
           return channels;
       }

=========================================

彩色影像整張進行每個像素點簡單減法運算

blue channel – 10

green channel – 20

red channel - 255

Mat dstMat = new Mat();
        
           Image<Gray, byte>[] channels;
           channels = img.Split();
           channels[0] -= 10;
           channels[1] -= 20;
           channels[2] -= 255;
           using (VectorOfMat vm = new VectorOfMat(channels[0].Mat, channels[1].Mat, channels[2].Mat))
           {
               CvInvoke.Merge(vm, dstMat); 
           }
           imageBox2.Image = dstMat;