高质量无损图片压缩算法

using System.Drawing;using System.Drawing.Imaging;using System.IO;namespace CompressImageHelper{    public class CompressImage    {        /// 
        /// 无损压缩图片        /// 
        /// 原图片地址        /// 压缩后保存图片地址        /// 压缩质量（数字越小压缩率越高）1-100        /// 压缩后图片的最大大小        /// 是否是第一次调用        /// 
             public static bool CompressImg(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true)        {            //如果是第一次调用，原始图像的大小小于要压缩的大小，则直接复制文件，并且返回true            FileInfo firstFileInfo = new FileInfo(sFile);            if (sfsc == true && firstFileInfo.Length < size * 1024)            {                firstFileInfo.CopyTo(dFile);                return true;            }            Image iSource = Image.FromFile(sFile);            ImageFormat tFormat = iSource.RawFormat;            int dHeight = iSource.Height / 2;            int dWidth = iSource.Width / 2;            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.Width * 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 = System.Drawing.Drawing2D.CompositingQuality.HighQuality;            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;            g.InterpolationMode = System.Drawing.Drawing2D.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                    FileInfo fi = new FileInfo(dFile);                    if (fi.Length > 1024 * size)                    {                        flag = flag - 10;                        CompressImg(sFile, dFile, flag, size, false);                    }                }                else                {                    ob.Save(dFile, tFormat);                }                return true;            }            catch            {                return false;            }            finally            {                iSource.Dispose();                ob.Dispose();            }        }    }}

调用示例：

private void button1_Click(object sender, EventArgs e)        {            if (openFileDialog1.ShowDialog() == DialogResult.OK)            {                picfile1 = openFileDialog1.FileName;                string name = Path.GetFileName(picfile1);                CompressImage.CompressImg(picfile1, Common.gpath + "ClientFile\\" + name,50,500);            }            else                picfile1 = "";        }