C#的图片处理类，生成高质量缩略图,代码已测试过,效果很好

 

 public static void MakeSmallPic(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {

            try
            {

                System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

                int towidth = width;
                int toheight = height;

                int x = 0;
                int y = 0;
                int ow = originalImage.Width;
                int oh = originalImage.Height;

                switch (mode)
                {
                    case "HW"://指定高宽缩放（可能变形）                
                        break;
                    case "W"://指定宽，高按比例                    
                        toheight = originalImage.Height * width / originalImage.Width;
                        break;
                    case "H"://指定高，宽按比例
                        towidth = originalImage.Width * height / originalImage.Height;
                        break;
                    case "Cut"://指定高宽裁减（不变形）                
                        if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                        {
                            oh = originalImage.Height;
                            ow = originalImage.Height * towidth / toheight;
                            y = 0;
                            x = (originalImage.Width - ow) / 2;
                        }
                        else
                        {
                            ow = originalImage.Width;
                            oh = originalImage.Width * height / towidth;
                            x = 0;
                            y = (originalImage.Height - oh) / 2;
                        }
                        break;
                    default:
                        break;
                }

                //新建一个bmp图片
                System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

                //新建一个画板
                System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);

                //设置高质量插值法
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

                //设置高质量,低速度呈现平滑程度
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                //清空画布并以透明背景色填充
                g.Clear(System.Drawing.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 System.Drawing.Rectangle(0, 0, towidth, toheight),
                    new System.Drawing.Rectangle(x, y, ow, oh),
                    System.Drawing.GraphicsUnit.Pixel);

                try
                {
                    //以jpg格式保存缩略图
                    bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                }
                catch (System.Exception e)
                {
                    throw e;
                }
                finally
                {
                    originalImage.Dispose();
                    bitmap.Dispose();
                    g.Dispose();
                }
            }
            catch
            {
                throw;
            }
        }

 

C#的图片处理类，生成高质量缩略图,代码已测试过,效果很好