C#图片无损压缩

//引用命名空间
using System.Drawing.Imaging;
using System.Drawing;
using System.Drawing.Drawing2D;

#region GetPicThumbnail

///

/// 无损压缩图片

///

/// 原图片

/// 压缩后保存位置

/// 高度

///

/// 压缩质量 1-100

///

public bool GetPicThumbnail(string sFile, string dFile, int dHeight, int dWidth, int flag)

{

System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);

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) //将**改成c#中的或者操作符号

{

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();

}

}

     #endregion