图片的缩放以及剪切

借鉴的，总结下放一起拉。

public static class Imgs
    {
        /// <summary>
        /// 对上传的图片进行等比缩放
        /// </summary>
        /// <param name="fromFile">获取文件流Stream</param>
        /// <param name="fileSaveUrl">缩略图保存完整路径</param>
        /// <param name="targetWidth">模板宽度</param>
        /// <param name="targetHeight">模板高度</param>
        public static void ZoomPic(System.IO.Stream fromFile, string fileSaveUrl, System.Double targetWidth, System.Double targetHeight)
        {
            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
            Image initImage = Image.FromStream(fromFile, true);
            //原图宽高均小于模版，不作处理，直接保存
            if (initImage.Width <= targetWidth && initImage.Height <= targetHeight)
            {
                //保存
                initImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            else
            {
                //缩略图宽、高计算
                double newWidth = initImage.Width;
                double newHeight = initImage.Height;
                //宽大于高或宽等于高（横图或正方）
                if (initImage.Width > initImage.Height || initImage.Width == initImage.Height)
                {
                    //如果宽大于模版
                    if (initImage.Width > targetWidth)
                    {
                        //宽按模版，高按比例缩放
                        newWidth = targetWidth;
                        newHeight = initImage.Height * (targetWidth / initImage.Width);
                    }
                }
                //高大于宽（竖图）
                else
                {
                    //如果高大于模版
                    if (initImage.Height > targetHeight)
                    {
                        //高按模版，宽按比例缩放
                        newHeight = targetHeight;
                        newWidth = initImage.Width * (targetHeight / initImage.Height);
                    }
                }

                //生成新图
                //新建一个bmp图片
                Image newImage = new Bitmap((int)newWidth, (int)newHeight);
                //新建一个画板
                Graphics newG = Graphics.FromImage(newImage);
                //设置质量
                newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                //置背景色
                newG.Clear(Color.White);
                //画图
                newG.DrawImage(initImage, new Rectangle(0, 0, newImage.Width, newImage.Height), new Rectangle(0, 0, initImage.Width, initImage.Height), GraphicsUnit.Pixel);

                //保存缩略图
                newImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);
                //释放资源
                newG.Dispose();
                newImage.Dispose();
                initImage.Dispose();
            }
        }


        /// <summary>
        /// 无损压缩图片
        /// </summary>
        /// <param name="sFile">原图片</param>
        /// <param name="dFile">压缩后保存位置</param>
        /// <param name="dHeight">高度</param>
        /// <param name="dWidth">宽度</param>
        /// <param name="flag">压缩质量 1-100</param>
        /// <returns></returns>
        public static bool CompressImage(Stream stream, string dFile, int dHeight, int dWidth, int flag)
        {

            System.Drawing.Image iSource = System.Drawing.Image.FromStream(stream);
            ImageFormat tFormat = iSource.RawFormat;
            int sW = 0, sH = 0;
            //按比例缩放
            Size tem_size = new Size(iSource.Width, iSource.Height);

            if (tem_size.Width > dHeight || tem_size.Width > dWidth)
            {
                if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))
                {
                    sW = dWidth;
                    sH = (dWidth * tem_size.Height) / tem_size.Width;
                }
                else
                {
                    sH = dHeight;
                    sW = (tem_size.Width * dHeight) / tem_size.Height;
                }
            }
            else
            {
                sW = tem_size.Width;
                sH = tem_size.Height;
            }
            Bitmap ob = new Bitmap(dWidth, dHeight);
            Graphics g = Graphics.FromImage(ob);
            g.Clear(Color.WhiteSmoke);
            g.CompositingQuality = CompositingQuality.HighQuality;
            g.SmoothingMode = SmoothingMode.HighQuality;
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
            g.Dispose();
            //以下代码为保存图片时，设置压缩质量
            EncoderParameters ep = new EncoderParameters();
            long[] qy = new long[1];
            qy[0] = flag;//设置压缩的比例1-100
            EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
            ep.Param[0] = eParam;
            try
            {
                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                ImageCodecInfo jpegICIinfo = null;
                for (int x = 0; x < arrayICI.Length; x++)
                {
                    if (arrayICI[x].FormatDescription.Equals("JPEG"))
                    {
                        jpegICIinfo = arrayICI[x];
                        break;
                    }
                }
                if (jpegICIinfo != null)
                {
                    ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
                }
                else
                {
                    ob.Save(dFile, tFormat);
                }
                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                iSource.Dispose();
                ob.Dispose();
            }

        }


        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            WebRequest wr = WebRequest.Create(originalImagePath);
            WebResponse res = wr.GetResponse();
            Image originalImage = Image.FromStream(res.GetResponseStream());
            //System.Drawing.Image.FromFile(originalImagePath);
            //originalImagePath 来源路径
            //thumbnailPath 目的路径
            //width 源图片宽
            //height 源图片高
            //mode 缩放模式

            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;
                case "D":
                    if ((double)originalImage.Width > (double)originalImage.Height)
                    {
                        toheight = originalImage.Height * width / originalImage.Width;
                    }
                    else
                    {
                        towidth = originalImage.Width * height / originalImage.Height;
                    }
                    break;
                default:
                    break;
            }

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

            //新建一个画板
            Graphics g = 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(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, towidth, toheight),
             new Rectangle(x, y, ow, oh),
             GraphicsUnit.Pixel);

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

    }