你可以使用C#中的System.Drawing命名空间来实现图片的压缩。下面是一个简单的示例代码，演示如何将图片压缩到指定的大小：

using System;using System.Drawing;using System.Drawing.Imaging;using System.IO;public class ImageCompressor{public void CompressImage(string sourcePath, string outputPath, int maxWidth, int maxHeight){using (Image sourceImage = Image.FromFile(sourcePath)){double aspectRatio = (double)sourceImage.Width / sourceImage.Height;int newWidth = maxWidth;int newHeight = (int)(maxWidth / aspectRatio);if (newHeight > maxHeight){newHeight = maxHeight;newWidth = (int)(maxHeight * aspectRatio);}using (Bitmap compressedImage = new Bitmap(newWidth, newHeight)){using (Graphics graphics = Graphics.FromImage(compressedImage)){graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;graphics.DrawImage(sourceImage, 0, 0, newWidth, newHeight);}compressedImage.Save(outputPath, ImageFormat.Jpeg);}}}}class Program{static void Main(){ImageCompressor compressor = new ImageCompressor();compressor.CompressImage("source.jpg", "compressed.jpg", 800, 600);}}

在上面的示例代码中，CompressImage方法接受源图片的路径、输出路径以及目标宽度和高度作为参数。算法会计算出适合目标宽度和高度的图片尺寸，并将源图片按照这个尺寸进行压缩保存为JPEG格式。您可以根据需要调整压缩质量和输出格式。