柯乐义图片压缩类，本类可以将图片按指定的宽和高生成缩略图，同时压缩文件，如果指定的高宽和原图一样则只压缩图片的大小不改变尺寸，还可以指定压缩的质量。
WinForm示例下载地址：http://download.keleyi.com/source/keleyithumbnail.rar
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
namespace Keleyi.Com.Framework
{
public class KeleyiThumbnail
{
#region SaveKeleyiThumbnail
/// <summary>
/// 无损压缩图片方法
/// </summary>
/// <param name="sFile">原图片全名</param>
/// <param name="dFile">压缩后保存文件全名，后缀请写.jpg</param>
/// <param name="dHeight">压缩后的宽度</param>
/// <param name="dWidth">压缩后的高度</param>
/// <param name="flag">压缩质量 1-100</param>
/// <returns>是否成功</returns>
public static bool SaveKeleyiThumbnail(string sFile, string dFile, int dWidth, int dHeight, int flag)
{
Image iSource = 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)
{
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
}
}