C#图像处理OpenCV开发指南（CVStar，06）——图片光滑处理之高斯滤波（GaussianBlur）的实现代码

1 高斯滤波

原理就不讲了，文章很多。

基础代码请参阅：

C#图像处理OpenCV开发指南（CVStar，03）——基于.NET 6的图像处理桌面程序开发实践第一步https://blog.csdn.net/beijinghorn/article/details/134684471?spm=1001.2014.3001.5502

1.1 函数原型

void GaussianBlur(src, dst, ksize, sigmaX, sigmaY, borderType)

1.2 参数说明

src 是需要处理的图像，即原始图像。它能够有任意数量的通道，并能对各个通道独立处理。图像深度应该是CV_8U、CV_16U、CV_16S、CV_32F 或者 CV_64F中的一种。
dst 是返回值，表示进行高斯滤波后得到的处理结果。
ksize 是滤波核的大小。滤波核大小是指在滤波处理过程中其邻域图像的高度和宽度。需要注意，滤波核的值必须是奇数。
sigmaX 是卷积核在水平方向上（X 轴方向）的标准差，其控制的是权重比例。
sigmaY 是卷积核在垂直方向上（Y轴方向）的标准差。如果将该值设置为0，则只采用sigmaX的值
如果sigmaX和sigmaY都是0，则通过ksize.width和ksize.height计算得到。其中：
sigmaX=0.3 × [（ksize.width-1）×0.5-1] + 0.8
sigmaY=0.3 × [（ksize.height-1）×0.5-1] + 0.8
borderType是边界样式，该值决定了以何种方式处理边界。一般情况下，不需要考虑该值，直接采用默认值即可。

在该函数中，sigmaY和borderType是可选参数。
sigmaX是必选参数，但是可以将该参数设置为0，让函数自己去计算sigmaX的具体值。

1.3 C++例子程序

#include <iostream>
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
using namespace std;
using namespace cv;
int DELAY_CAPTION = 1500;
int DELAY_BLUR = 100;
int MAX_KERNEL_LENGTH = 31;
Mat src; Mat dst;
char window_name[] = "Smoothing Demo";
int display_caption( const char* caption );
int display_dst( int delay );
int main( int argc, char ** argv )
{
    namedWindow( window_name, WINDOW_AUTOSIZE );
    const char* filename = argc >=2 ? argv[1] : "lena.jpg";
    src = imread( samples::findFile( filename ), IMREAD_COLOR );
    if (src.empty())
    {
        printf(" Error opening image\n");
        printf(" Usage:\n %s [image_name-- default lena.jpg] \n", argv[0]);
        return EXIT_FAILURE;
    }
    if( display_caption( "Original Image" ) != 0 )
    {
        return 0;
    }
    dst = src.clone();
    if( display_dst( DELAY_CAPTION ) != 0 )
    {
        return 0;
    }
    if( display_caption( "Homogeneous Blur" ) != 0 )
    {
        return 0;
    }
    for ( int i = 1; i < MAX_KERNEL_LENGTH; i = i + 2 )
    {
        blur( src, dst, Size( i, i ), Point(-1,-1) );
        if( display_dst( DELAY_BLUR ) != 0 )
        {
            return 0;
        }
    }
    if( display_caption( "Gaussian Blur" ) != 0 )
    {
        return 0;
    }
    for ( int i = 1; i < MAX_KERNEL_LENGTH; i = i + 2 )
    {
        GaussianBlur( src, dst, Size( i, i ), 0, 0 );
        if( display_dst( DELAY_BLUR ) != 0 )
        {
            return 0;
        }
    }
    if( display_caption( "Median Blur" ) != 0 )
    {
        return 0;
    }
    for ( int i = 1; i < MAX_KERNEL_LENGTH; i = i + 2 )
    {
        medianBlur ( src, dst, i );
        if( display_dst( DELAY_BLUR ) != 0 )
        {
            return 0;
        }
    }
    if( display_caption( "Bilateral Blur" ) != 0 )
    {
        return 0;
    }
    for ( int i = 1; i < MAX_KERNEL_LENGTH; i = i + 2 )
    {
        bilateralFilter ( src, dst, i, i*2, i/2 );
        if( display_dst( DELAY_BLUR ) != 0 )
        {
            return 0;
        }
    }
    display_caption( "Done!" );
    return 0;
}
int display_caption( const char* caption )
{
    dst = Mat::zeros( src.size(), src.type() );
    putText( dst, caption,
             Point( src.cols/4, src.rows/2),
             FONT_HERSHEY_COMPLEX, 1, Scalar(255, 255, 255) );
    return display_dst(DELAY_CAPTION);
}
int display_dst( int delay )
{
    imshow( window_name, dst );
    int c = waitKey ( delay );
    if( c >= 0 ) { return -1; }
    return 0;
}

2 高斯滤波的代码

2.1 参数输入的界面相关代码


if (abKSize == null) abKSize = new Label();
abKSize.Parent = panelTop;
abKSize.Left = btnFunction.Left;
abKSize.Top = btnFunction.Top + btnFunction.Height + 5;
abKSize.Text = "Radium: ";

if (txtKSize == null) txtKSize = new TextBox();
txtKSize.Parent = panelTop;
txtKSize.Left = abKSize.Left + abKSize.Width + 5;
txtKSize.Top = abKSize.Top;
txtKSize.Text = "15";

if (abSigmaX == null) abSigmaX = new Label();
abSigmaX.Parent = panelTop;
abSigmaX.Left = txtKSize.Left + txtKSize.Width + 5;
abSigmaX.Top = btnFunction.Top + btnFunction.Height + 5;
abSigmaX.Text = "SigmaX: ";

if (txtSigmaX == null) txtSigmaX = new TextBox();
txtSigmaX.Parent = panelTop;
txtSigmaX.Left = abSigmaX.Left + abSigmaX.Width + 5;
txtSigmaX.Top = abKSize.Top;
txtSigmaX.Text = "0.0";

if (abSigmaY == null) abSigmaY = new Label();
abSigmaY.Parent = panelTop;
abSigmaY.Left = txtSigmaX.Left + txtSigmaX.Width + 5;
abSigmaY.Top = btnFunction.Top + btnFunction.Height + 5;
abSigmaY.Text = "SigmaX: ";

if (txtSigmaY == null) txtSigmaY = new TextBox();
txtSigmaY.Parent = panelTop;
txtSigmaY.Left = abSigmaY.Left + abSigmaY.Width + 5;
txtSigmaY.Top = abKSize.Top;
txtSigmaY.Text = "0.0";

2.2 核心代码

private void GaussianBlur(object? sender, EventArgs? e)
{
    if (txtKSize.Text.Trim().Length < 1) { MessageBox.Show("rad Required!"); return; }
    if (!int.TryParse(txtKSize.Text.Trim(), out int ksize)) { MessageBox.Show("Invalid rad number!"); return; }
    if (ksize < 1 || ksize > 100) { MessageBox.Show("Invalid rad number!"); return; }
    if ((ksize % 2) != 1) { MessageBox.Show("Odd number required for rad!"); return; }

    if (txtSigmaX.Text.Trim().Length < 1) { MessageBox.Show("SigmaX Required!"); return; }
    if (!double.TryParse(txtSigmaX.Text.Trim(), out double sigmax)) { MessageBox.Show("Invalid SigmaX!"); return; }
    if (sigmax < -1.0 || sigmax > 1.0) { MessageBox.Show("Invalid sigmaX（-1.0---1.0）!"); return; }
    
    if (txtSigmaY.Text.Trim().Length < 1) { MessageBox.Show("SigmaY Required!"); return; }
    if (!double.TryParse(txtSigmaY.Text.Trim(), out double sigmay)) { MessageBox.Show("Invalid SigmaY!"); return; }
    if (sigmay < -1.0 || sigmay > 1.0) { MessageBox.Show("Invalid sigmaY（-1.0---1.0）!"); return; }

    Mat src = Cv2.ImRead(sourceImage);
    Mat dst = new Mat();
    Cv2.GaussianBlur(
        src: src,
        dst: dst,
        ksize: new OpenCvSharp.Size(ksize, ksize),
        sigmaX: sigmax,
        sigmaY: sigmay,
        borderType: BorderTypes.Default);
    picResult.Image = CVUtility.Mat2Bitmap(dst);
    PicAutosize(picResult);
}

3 完整的 Form1.cs 代码

using OpenCvSharp;

#pragma warning disable CS8602

namespace Legal.Truffer.CVStar
{
    public partial class Form1 : Form
    {
        string[] ImgExtentions = {
            "*.*|*.*",
            "JPEG|*.jpg;*.jpeg",
            "GIF|*.gif",
            "PNG|*.png",
            "TIF|*.tif;*.tiff",
            "BMP|*.bmp"
        };
        private int original_width { get; set; } = 0;
        private int original_height { get; set; } = 0;
        private string sourceImage { get; set; } = "";

        Panel? panelTop { get; set; } = null;
        Panel? panelBotton { get; set; } = null;
        PictureBox? picSource { get; set; } = null;
        PictureBox? picResult { get; set; } = null;
        Button? btnLoad { get; set; } = null;
        Button? btnSave { get; set; } = null;
        Button? btnFunction { get; set; } = null;

        Label? abKSize { get; set; } = null;
        TextBox? txtKSize { get; set; } = null;
        Label? abSigmaX { get; set; } = null;
        TextBox? txtSigmaX { get; set; } = null;
        Label? abSigmaY { get; set; } = null;
        TextBox? txtSigmaY { get; set; } = null;

        public Form1()
        {
            InitializeComponent();

            this.Text = "OPENCV C#编程入手教程 POWERED BY 深度混淆（CSDN.NET）";
            this.StartPosition = FormStartPosition.CenterScreen;

            GUI();
            this.Resize += FormResize;
        }

        private void FormResize(object? sender, EventArgs? e)
        {
            if (this.Width < 200) { this.Width = 320; return; }
            if (this.Height < 200) { this.Height = 320; return; }
            GUI();
        }

        private void GUI()
        {
            if (panelTop == null) panelTop = new Panel();
            panelTop.Parent = this;
            panelTop.Top = 5;
            panelTop.Left = 5;
            panelTop.Width = this.Width - 26;
            panelTop.Height = 85;
            panelTop.BorderStyle = BorderStyle.FixedSingle;
            panelTop.BackColor = Color.FromArgb(200, 200, 255);

            if (panelBotton == null) panelBotton = new Panel();
            panelBotton.Parent = this;
            panelBotton.Top = panelTop.Top + panelTop.Height + 3;
            panelBotton.Left = 5;
            panelBotton.Width = panelTop.Width;
            panelBotton.Height = this.Height - panelBotton.Top - 55;
            panelBotton.BorderStyle = BorderStyle.FixedSingle;

            if (picSource == null) picSource = new PictureBox();
            picSource.Parent = panelBotton;
            picSource.Left = 5;
            picSource.Top = 5;
            picSource.Width = (panelBotton.Width - 10) / 2;
            picSource.Height = (panelBotton.Height - 10);
            picSource.BorderStyle = BorderStyle.FixedSingle;

            if (picResult == null) picResult = new PictureBox();
            picResult.Parent = panelBotton;
            picResult.Left = picSource.Left + picSource.Width + 5;
            picResult.Top = picSource.Top;
            picResult.Width = picSource.Width;
            picResult.Height = picSource.Height;
            picResult.BorderStyle = BorderStyle.FixedSingle;

            original_width = picSource.Width;
            original_height = picSource.Height;

            if (btnLoad == null) btnLoad = new Button();
            btnLoad.Parent = panelTop;
            btnLoad.Left = 5;
            btnLoad.Top = 5;
            btnLoad.Width = 90;
            btnLoad.Height = 38;
            btnLoad.Cursor = Cursors.Hand;
            btnLoad.Text = "Load";
            btnLoad.Click += Load_Image;
            btnLoad.BackColor = Color.LightCoral;

            if (btnSave == null) btnSave = new Button();
            btnSave.Parent = panelTop;
            btnSave.Left = panelTop.Width - btnSave.Width - 25;
            btnSave.Top = btnLoad.Top;
            btnSave.Width = 90;
            btnSave.Height = 38;
            btnSave.Cursor = Cursors.Hand;
            btnSave.Text = "Save";
            btnSave.Click += Save;
            btnSave.BackColor = Color.LightCoral;

            if (btnFunction == null) btnFunction = new Button();
            btnFunction.Parent = panelTop;
            btnFunction.Left = btnLoad.Left + btnLoad.Width + 5;
            btnFunction.Top = btnLoad.Top;
            btnFunction.Width = 90;
            btnFunction.Height = 38;
            btnFunction.Cursor = Cursors.Hand;
            btnFunction.Text = "GaussianBlur";
            btnFunction.Click += GaussianBlur;
            btnFunction.BackColor = Color.LightCoral;

            if (abKSize == null) abKSize = new Label();
            abKSize.Parent = panelTop;
            abKSize.Left = btnFunction.Left;
            abKSize.Top = btnFunction.Top + btnFunction.Height + 5;
            abKSize.Text = "Radium: ";

            if (txtKSize == null) txtKSize = new TextBox();
            txtKSize.Parent = panelTop;
            txtKSize.Left = abKSize.Left + abKSize.Width + 5;
            txtKSize.Top = abKSize.Top;
            txtKSize.Text = "15";

            if (abSigmaX == null) abSigmaX = new Label();
            abSigmaX.Parent = panelTop;
            abSigmaX.Left = txtKSize.Left + txtKSize.Width + 5;
            abSigmaX.Top = btnFunction.Top + btnFunction.Height + 5;
            abSigmaX.Text = "SigmaX: ";

            if (txtSigmaX == null) txtSigmaX = new TextBox();
            txtSigmaX.Parent = panelTop;
            txtSigmaX.Left = abSigmaX.Left + abSigmaX.Width + 5;
            txtSigmaX.Top = abKSize.Top;
            txtSigmaX.Text = "0.0";

            if (abSigmaY == null) abSigmaY = new Label();
            abSigmaY.Parent = panelTop;
            abSigmaY.Left = txtSigmaX.Left + txtSigmaX.Width + 5;
            abSigmaY.Top = btnFunction.Top + btnFunction.Height + 5;
            abSigmaY.Text = "SigmaX: ";

            if (txtSigmaY == null) txtSigmaY = new TextBox();
            txtSigmaY.Parent = panelTop;
            txtSigmaY.Left = abSigmaY.Left + abSigmaY.Width + 5;
            txtSigmaY.Top = abKSize.Top;
            txtSigmaY.Text = "0.0";

            PicAutosize(picSource);
            PicAutosize(picResult);
        }

        private void Load_Image(object? sender, EventArgs? e)
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = String.Join("|", ImgExtentions);
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                sourceImage = openFileDialog.FileName;
                picSource.Image = Image.FromFile(sourceImage);
                picResult.Image = picSource.Image;
                PicAutosize(picSource);
                PicAutosize(picResult);
            }
        }

        private void PicAutosize(PictureBox pb)
        {
            if (pb == null) return;
            if (pb.Image == null) return;
            Image img = pb.Image;
            int w = original_width;
            int h = w * img.Height / img.Width;
            if (h > original_height)
            {
                h = original_height;
                w = h * img.Width / img.Height;
            }
            pb.SizeMode = PictureBoxSizeMode.Zoom;
            pb.Width = w;
            pb.Height = h;
            pb.Image = img;
            pb.Refresh();
        }

        private void Save(object? sender, EventArgs? e)
        {
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = String.Join("|", ImgExtentions);
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                picResult.Image.Save(saveFileDialog.FileName);
                MessageBox.Show("Image Save to " + saveFileDialog.FileName);
            }
        }

        private void GaussianBlur(object? sender, EventArgs? e)
        {
            if (txtKSize.Text.Trim().Length < 1) { MessageBox.Show("rad Required!"); return; }
            if (!int.TryParse(txtKSize.Text.Trim(), out int ksize)) { MessageBox.Show("Invalid rad number!"); return; }
            if (ksize < 1 || ksize > 100) { MessageBox.Show("Invalid rad number!"); return; }
            if ((ksize % 2) != 1) { MessageBox.Show("Odd number required for rad!"); return; }

            if (txtSigmaX.Text.Trim().Length < 1) { MessageBox.Show("SigmaX Required!"); return; }
            if (!double.TryParse(txtSigmaX.Text.Trim(), out double sigmax)) { MessageBox.Show("Invalid SigmaX!"); return; }
            if (sigmax < -1.0 || sigmax > 1.0) { MessageBox.Show("Invalid sigmaX（-1.0---1.0）!"); return; }
            
            if (txtSigmaY.Text.Trim().Length < 1) { MessageBox.Show("SigmaY Required!"); return; }
            if (!double.TryParse(txtSigmaY.Text.Trim(), out double sigmay)) { MessageBox.Show("Invalid SigmaY!"); return; }
            if (sigmay < -1.0 || sigmay > 1.0) { MessageBox.Show("Invalid sigmaY（-1.0---1.0）!"); return; }

            Mat src = Cv2.ImRead(sourceImage);
            Mat dst = new Mat();
            Cv2.GaussianBlur(
                src: src,
                dst: dst,
                ksize: new OpenCvSharp.Size(ksize, ksize),
                sigmaX: sigmax,
                sigmaY: sigmay,
                borderType: BorderTypes.Default);
            picResult.Image = CVUtility.Mat2Bitmap(dst);
            PicAutosize(picResult);
        }

    }
}