Windows Forms:在C#中将图像转换成灰度图

本文翻译自Windows Forms: Convert an image into grayscale in C#
这篇文章向你展示在C# Windows窗体应用程序中如何将图像转换成灰度图。
创建一个新的Windows窗体应用程序项目，然后创建一个允许你可以打开图像，然后将图像转换成黑白图像的简单的UI，如下图所示：

Convert Image

private void btnOpen_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog openFileDlg = new OpenFileDialog() { Filter = "Images|*.jpg" })
            {
                if (openFileDlg.ShowDialog() == DialogResult.OK)
                {
                    picOriginal.Image = Image.FromFile(openFileDlg.FileName);
                }
            }
        }

下一步，创建一个MakeGrayscale方法允许你在C#中将图像转换成灰度图如下：

//  convert an image into grayscale in c#
        public Bitmap MakeGrayscale(Bitmap original)
        {
            // You need to create a new bitmap with size the same as image original, 
            // then create a color matrix and convert a color image to grayscale with C#.
            Bitmap newBmp = new Bitmap(original.Width, original.Height);
            Graphics g = Graphics.FromImage(newBmp);
            ColorMatrix colorMatrix = new ColorMatrix(
               new float[][]
               {
                   new float[] {.3f, .3f, .3f, 0, 0},
                   new float[] {.59f, .59f, .59f, 0, 0},
                   new float[] {.11f, .11f, .11f, 0, 0},
                   new float[] {0, 0, 0, 1, 0},
                   new float[] {0, 0, 0, 0, 1}
               });
            ImageAttributes img = new ImageAttributes();
            img.SetColorMatrix(colorMatrix);
            g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height), 0, 0, original.Width, original.Height, GraphicsUnit.Pixel, img);
            g.Dispose();
            return newBmp;
        }

你需要创建一个和原图像一样大小的位图，然后创建一个颜色矩阵，并在C#中将彩色图转换成灰度图。
最后，为Convert按钮添加事件处理，允许你将图像转换成灰度图：

private void btnConvert_Click(object sender, EventArgs e)
        {
            picConvert.Image = MakeGrayscale((Bitmap)picOriginal.Image);
        }

下面是窗体的完整实现代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace ConvertImageIntoGrayscale
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //  convert an image into grayscale in c#
        public Bitmap MakeGrayscale(Bitmap original)
        {
            // You need to create a new bitmap with size the same as image original, 
            // then create a color matrix and convert a color image to grayscale with C#.
            Bitmap newBmp = new Bitmap(original.Width, original.Height);
            Graphics g = Graphics.FromImage(newBmp);
            ColorMatrix colorMatrix = new ColorMatrix(
               new float[][]
               {
                   new float[] {.3f, .3f, .3f, 0, 0},
                   new float[] {.59f, .59f, .59f, 0, 0},
                   new float[] {.11f, .11f, .11f, 0, 0},
                   new float[] {0, 0, 0, 1, 0},
                   new float[] {0, 0, 0, 0, 1}
               });
            ImageAttributes img = new ImageAttributes();
            img.SetColorMatrix(colorMatrix);
            g.DrawImage(original, new Rectangle(0, 0, original.Width, original.Height), 0, 0, original.Width, original.Height, GraphicsUnit.Pixel, img);
            g.Dispose();
            return newBmp;
        }

        private void btnOpen_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog openFileDlg = new OpenFileDialog() { Filter = "Images|*.jpg" })
            {
                if (openFileDlg.ShowDialog() == DialogResult.OK)
                {
                    picOriginal.Image = Image.FromFile(openFileDlg.FileName);
                }
            }
        }

        private void btnConvert_Click(object sender, EventArgs e)
        {
            picConvert.Image = MakeGrayscale((Bitmap)picOriginal.Image);
        }
    }
}

lena图像素材下载

图像处理中经常使用到的Lena图片 下载地址：
https://bellard.org/bpg/lena.html

http://www.lenna.org/

Lena的图片

http://www.lenna.org/

程序效果

程序效果展示

参考资料

• Windows Forms: Convert an image into grayscale in C#
• https://bellard.org/bpg/lena.html
• http://www.lenna.org/