C#对图片进行缩放变换

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.Windows.Forms;

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

        private void button1_Click(object sender, EventArgs e)
        {
            Image s = Image.FromFile("D:\\image\\22.jpg");
            Image bgImage = ZoomPicture(s, 0.5f, 0.5f);  //M,N大于1，为放大图片，小于1为缩小图片
            panel1.Width = bgImage.Width;  //设置画板宽度为图片宽度
            panel1.Height = bgImage.Height; //设置画板高度为图片高度
            panel1.BackgroundImage = bgImage;
            BitMap bmap = new BitMap(bgImage);    
            bmap.Save("D:\\image\\23.jpg", ImageFormt.Jpeg);
            bmap.Dispose();
        }

        // 按比例缩放图片
        public Image ZoomPicture(Image SourceImage, float M, float N)
        {
            int IntWidth; //新的图片宽
            int IntHeight; //新的图片高
            int TargetWidth = (int)(M * SourceImage.Width); //取整，是因为下面的Bitmap的两个参数只能为整数
            int TargetHeight = (int)(N * SourceImage.Height);
            try
            {
                ImageFormat format = SourceImage.RawFormat;
                Bitmap SaveImage = new Bitmap(TargetWidth, TargetHeight);
                Graphics g = Graphics.FromImage(SaveImage);
                g.Clear(Color.White);

                //计算缩放图片的大小
                IntHeight = TargetHeight;
                IntWidth = TargetWidth;
                g.DrawImage(SourceImage, 0, 0, IntWidth, IntHeight); //在指定坐标处画指定大小的图片
                SourceImage.Dispose();

                return SaveImage;
            }
            catch (Exception ex)
            {

            }

            return null;
        }
    }
}