Asp.net 实现图片缩放 无水印（方法一）

/// <summary>

        /// 图片缩放   无水印

        /// </summary>

        /// <param name="sourceFile">图片源路径</param>

        /// <param name="destFile">缩放后图片输出路径</param>

        /// <param name="destHeight">缩放后图片高度</param>

        /// <param name="destWidth">缩放后图片宽度</param>

        /// <returns></returns>

        public static bool GetThumbnail(string sourceFile, string destFile, int destHeight, int destWidth)

        {

            System.Drawing.Image imgSource = System.Drawing.Image.FromFile(sourceFile);

            System.Drawing.Imaging.ImageFormat thisFormat = imgSource.RawFormat;

            int sW = 0, sH = 0;

            // 按比例缩放

            int sWidth = imgSource.Width;

            int sHeight = imgSource.Height;



            if (sHeight > destHeight || sWidth > destWidth)

            {

                if ((sWidth * destHeight) > (sHeight * destWidth))

                {

                    sW = destWidth;

                    sH = (destWidth * sHeight) / sWidth;

                }

                else

                {

                    sH = destHeight;

                    sW = (sWidth * destHeight) / sHeight;

                }

            }

            else

            {

                sW = sWidth;

                sH = sHeight;

            }



            Bitmap outBmp = new Bitmap(destWidth, destHeight);

            Graphics g = Graphics.FromImage(outBmp);

            g.Clear(Color.WhiteSmoke);



            // 设置画布的描绘质量

            g.CompositingQuality = CompositingQuality.HighQuality;

            g.SmoothingMode = SmoothingMode.HighQuality;

            g.InterpolationMode = InterpolationMode.HighQualityBicubic;



            g.DrawImage(imgSource, new Rectangle((destWidth - sW) / 2, (destHeight - sH) / 2, sW, sH), 0, 0, imgSource.Width, imgSource.Height, GraphicsUnit.Pixel);

           



            // 以下代码为保存图片时，设置压缩质量

            EncoderParameters encoderParams = new EncoderParameters();

            long[] quality = new long[1];

            quality[0] = 100;



            EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);

            encoderParams.Param[0] = encoderParam;



            try

            {

                //获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。

                ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();

                ImageCodecInfo jpegICI = null;

                for (int x = 0; x < arrayICI.Length; x++)

                {

                    if (arrayICI[x].FormatDescription.Equals("JPEG"))

                    {

                        jpegICI = arrayICI[x];//设置JPEG编码

                        break;

                    }

                }



                if (jpegICI != null)

                {

                    outBmp.Save(destFile, jpegICI, encoderParams);

                }

                else

                {

                    outBmp.Save(destFile, thisFormat);

                }

                imgSource.Dispose();

                outBmp.Dispose();

                g.Dispose();

                return true;

            }

            catch

            {

                return false;

            }

            finally

            {

            }

        }