批量图片压缩工具

 /// <summary>
        /// 获取缩略图
        /// </summary>
        /// <param name="bitmap"></param>
        /// <param name="width"></param>
        /// <returns></returns>
        public static Image GetThumbnailImageByte(Image bitmap, int width)
        {
            System.Drawing.Image img = bitmap.Clone() as Image;

            if (bitmap.RawFormat == System.Drawing.Imaging.ImageFormat.Gif)
            {
                #region gif动态图缩放
                //不够100*100的不缩放
                if (img.Width > width)
                {
                    System.IO.MemoryStream stream = new System.IO.MemoryStream();
                    var height = (img.Height * width) / img.Width;
                    //新图第一帧
                    Image new_img = new Bitmap(width, height);
                    //新图其他帧
                    Image new_imgs = new Bitmap(width, height);
                    //新图第一帧GDI+绘图对象
                    Graphics g_new_img = Graphics.FromImage(new_img);
                    //新图其他帧GDI+绘图对象
                    Graphics g_new_imgs = Graphics.FromImage(new_imgs);
                    //配置新图第一帧GDI+绘图对象
                    g_new_img.CompositingMode = CompositingMode.SourceCopy;
                    g_new_img.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    g_new_img.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    g_new_img.SmoothingMode = SmoothingMode.HighQuality;
                    g_new_img.Clear(Color.FromKnownColor(KnownColor.Transparent));
                    //配置其他帧GDI+绘图对象
                    g_new_imgs.CompositingMode = CompositingMode.SourceCopy;
                    g_new_imgs.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    g_new_imgs.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    g_new_imgs.SmoothingMode = SmoothingMode.HighQuality;
                    g_new_imgs.Clear(Color.FromKnownColor(KnownColor.Transparent));
                    //遍历维数
                    foreach (Guid gid in img.FrameDimensionsList)
                    {
                        //因为是缩小GIF文件所以这里要设置为Time
                        //如果是TIFF这里要设置为PAGE
                        FrameDimension f = FrameDimension.Time;
                        //获取总帧数
                        int count = img.GetFrameCount(f);
                        //保存标示参数
                        System.Drawing.Imaging.Encoder encoder = System.Drawing.Imaging.Encoder.SaveFlag;
                        //
                        EncoderParameters ep = null;
                        //图片编码、解码器
                        ImageCodecInfo ici = null;
                        //图片编码、解码器集合
                        ImageCodecInfo[] icis = ImageCodecInfo.GetImageDecoders();
                        //为 图片编码、解码器 对象 赋值
                        foreach (ImageCodecInfo ic in icis)
                        {
                            if (ic.FormatID == ImageFormat.Gif.Guid)
                            {
                                ici = ic;
                                break;
                            }
                        }
                        //每一帧
                        for (int c = 0; c < count; c++)
                        {
                            //选择由维度和索引指定的帧
                            img.SelectActiveFrame(f, c);
                            //第一帧
                            if (c == 0)
                            {
                                //将原图第一帧画给新图第一帧
                                g_new_img.DrawImage(img, new Rectangle(0, 0, width, height), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);
                                //把振频和透明背景调色板等设置复制给新图第一帧
                                for (int i = 0; i < img.PropertyItems.Length; i++)
                                {
                                    new_img.SetPropertyItem(img.PropertyItems[i]);
                                }
                                ep = new EncoderParameters(1);
                                //第一帧需要设置为MultiFrame
                                ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.MultiFrame);
                                //保存第一帧
                                new_img.Save(stream, ici, ep);
                            }
                            //其他帧
                            else
                            {
                                //把原图的其他帧画给新图的其他帧
                                g_new_imgs.DrawImage(img, new Rectangle(0, 0, width, height), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);
                                //把振频和透明背景调色板等设置复制给新图第一帧
                                for (int i = 0; i < img.PropertyItems.Length; i++)
                                {
                                    new_imgs.SetPropertyItem(img.PropertyItems[i]);
                                }
                                ep = new EncoderParameters(1);
                                //如果是GIF这里设置为FrameDimensionTime
                                //如果为TIFF则设置为FrameDimensionPage
                                ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.FrameDimensionTime);
                                //向新图添加一帧
                                new_img.SaveAdd(new_imgs, ep);
                            }
                        }
                        ep = new EncoderParameters(1);
                        //关闭多帧文件流
                        ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.Flush);
                        new_img.SaveAdd(ep);
                    }
                    byte[] byData = new Byte[stream.Length];
                    stream.Position = 0;
                    stream.Read(byData, 0, byData.Length);
                    stream.Close();
                    //释放文件
                    img.Dispose();
                    new_img.Dispose();
                    new_imgs.Dispose();
                    g_new_img.Dispose();
                    g_new_imgs.Dispose();
                    return BytesToBitmap(byData);
                }
                #endregion
            }
            else
            {
                #region 静态缩略图
                if (img.Width > width)
                {
                    Graphics g = null;
                    try
                    {
                        var height = (img.Height * width) / img.Width;
                        Bitmap bmpDest = new Bitmap(width, height);
                        g = Graphics.FromImage(bmpDest);
                        //g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Default;
                        g.Clear(Color.White);
                        g.DrawImage(img, new Rectangle(0, 0, width, height), new Rectangle(0, 0, img.Size.Width, img.Size.Height), GraphicsUnit.Pixel);
                        g.Flush();
                        return bmpDest;
                    }
                    catch
                    {
                        return null;
                    }
                    finally
                    {
                        g.Dispose();
                        img.Dispose();
                    }
                }
                #endregion
            }
            return img;
        }