c# 生成自定义图片

using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
using System;

namespace treads
{
    /// <summary>
    /// 生成略缩图
    /// </summary>
    public class Class2
    {
        private Image srcImage;
        private string srcFileName= @"X";//获取图片的路径
        private string srcFileName1 = @"x";//要保持图片的新路径

        /// <summary>
        /// 回调
        /// </summary>
        /// <returns></returns>
        public bool ThumbnailCallback()
        {
            return false;
        }
        /// <summary>
        /// 保存缩略图
        /// </summary>
        /// <param name="Width"></param>
        /// <param name="Height"></param>
        public void SaveThumbnailImage(int Width, int Height)
        {
            switch (Path.GetExtension(srcFileName).ToLower())
            {
                case ".png":
                    SaveImage(Width, Height, ImageFormat.Png);
                    break;
                case ".gif":
                    SaveImage(Width, Height, ImageFormat.Gif);
                    break;
                default:
                    SaveImage(Width, Height, ImageFormat.Jpeg);
                    break;
            }
        }

        /// <summary>
        /// 生成缩略图并保存
        /// </summary>
        /// <param name="Width">缩略图的宽度</param>
        /// <param name="Height">缩略图的高度</param>
        /// <param name="imgformat">保存的图像格式</param>
        /// <returns>缩略图的Image对象</returns>
        public void SaveImage(int Width, int Height, ImageFormat imgformat)
        {
            srcImage = Image.FromFile(srcFileName);
            if (imgformat != ImageFormat.Gif && (srcImage.Width > Width) || (srcImage.Height > Height))
            {
                Image img;
                Image.GetThumbnailImageAbort callb = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                img = srcImage.GetThumbnailImage(Width, Height, callb, IntPtr.Zero);
                srcImage.Dispose();
                img.Save(srcFileName1, imgformat);
                img.Dispose();
            }
        }

    }
}

 制作网络下载的略缩图

  /// <summary>
        /// 制作远程缩略图
        /// </summary>
        /// <param name="url">图片URL</param>
        /// <param name="newFileName">新图路径</param>
        /// <param name="maxWidth">最大宽度</param>
        /// <param name="maxHeight">最大高度</param>
        public static void MakeRemoteThumbnailImage(string url, string newFileName, int maxWidth, int maxHeight)
        {
            Stream stream = GetRemoteImage(url);
            if (stream == null)
                return;
            Image original = Image.FromStream(stream);
            stream.Close();
            MakeThumbnailImage(original, newFileName, maxWidth, maxHeight);
        }

   /// <summary>
        /// 获取图片流
        /// </summary>
        /// <param name="url">图片URL</param>
        /// <returns></returns>
        private static Stream GetRemoteImage(string url)
        {
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
            request.Method = "GET";
            request.ContentLength = 0;
            request.Timeout = 20000;
            HttpWebResponse response = null;

            try
            {
                response = (HttpWebResponse)request.GetResponse();
                return response.GetResponseStream();
            }
            catch
            {
                return null;
            }
        }

 /// <summary>
        /// 裁剪图片并保存
        /// </summary>
        /// <param name="fileName">源图路径（绝对路径）</param>
        /// <param name="newFileName">缩略图路径（绝对路径）</param>
        /// <param name="maxWidth">缩略图宽度</param>
        /// <param name="maxHeight">缩略图高度</param>
        /// <param name="cropWidth">裁剪宽度</param>
        /// <param name="cropHeight">裁剪高度</param>
        /// <param name="X">X轴</param>
        /// <param name="Y">Y轴</param>
        public static bool MakeThumbnailImage(string fileName, string newFileName, int maxWidth, int maxHeight, int cropWidth, int cropHeight, int X, int Y)
        {
            byte[] imageBytes = File.ReadAllBytes(fileName);
            Image originalImage = Image.FromStream(new System.IO.MemoryStream(imageBytes));
            Bitmap b = new Bitmap(cropWidth, cropHeight);
            try
            {
                using (Graphics g = Graphics.FromImage(b))
                {
                    //设置高质量插值法
                    g.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    //设置高质量,低速度呈现平滑程度
                    g.SmoothingMode = SmoothingMode.AntiAlias;
                    g.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    //清空画布并以透明背景色填充
                    g.Clear(Color.Transparent);
                    //在指定位置并且按指定大小绘制原图片的指定部分
                    g.DrawImage(originalImage, new Rectangle(0, 0, cropWidth, cropHeight), X, Y, cropWidth, cropHeight, GraphicsUnit.Pixel);
                    Image displayImage = new Bitmap(b, maxWidth, maxHeight);
                    SaveImage(displayImage, newFileName, GetCodecInfo("image/" + GetFormat(newFileName).ToString().ToLower()));
                    return true;
                }
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                b.Dispose();
            }
        }