View Code 
/// <summary> 
/// 按照比例缩小图片 
/// </summary> 
/// <param name="srcImage">要缩小的图片</param> 
/// <param name="percent">缩小比例</param> 
/// <returns>缩小后的结果</returns> 
public static Bitmap PercentImage(Image srcImage, double percent) 
{ 
// 缩小后的高度 
int newH = int.Parse(Math.Round(srcImage.Height * percent).ToString()); 
// 缩小后的宽度 
int newW = int.Parse(Math.Round(srcImage.Width * percent).ToString()); 
try 
{ 
// 要保存到的图片 
Bitmap b = new Bitmap(newW, newH); 
Graphics g = Graphics.FromImage(b); 
// 插值算法的质量 
g.InterpolationMode = InterpolationMode.Default; 
g.DrawImage(srcImage, new Rectangle(0, 0, newW, newH), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel); 
g.Dispose(); 
return b; 
} 
catch (Exception) 
{ 
return null; 
} 
} 

View Code 
/// <summary> 
/// 按照指定大小缩放图片 
/// </summary> 
/// <param name="srcImage"></param> 
/// <param name="iWidth"></param> 
/// <param name="iHeight"></param> 
/// <returns></returns> 
public static Bitmap SizeImage(Image srcImage, int iWidth, int iHeight) 
{ 
try 
{ 
// 要保存到的图片 
Bitmap b = new Bitmap(iWidth, iHeight); 
Graphics g = Graphics.FromImage(b); 
// 插值算法的质量 
g.InterpolationMode = InterpolationMode.HighQualityBicubic; 
g.DrawImage(srcImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, srcImage.Width, srcImage.Height), GraphicsUnit.Pixel); 
g.Dispose(); 
return b; 
} 
catch (Exception) 
{ 
return null; 
} 
} 

View Code 
/// <summary> 
/// 按照指定大小缩放图片，但是为了保证图片宽高比自动截取 
/// </summary> 
/// <param name="srcImage"></param> 
/// <param name="iWidth"></param> 
/// <param name="iHeight"></param> 
/// <returns></returns> 
public static Bitmap SizeImageWithOldPercent(Image srcImage, int iWidth, int iHeight) 
{ 
try 
{ 
// 要截取图片的宽度（临时图片） 
int newW = srcImage.Width; 
// 要截取图片的高度（临时图片） 
int newH = srcImage.Height; 
// 截取开始横坐标（临时图片） 
int newX = 0; 
// 截取开始纵坐标（临时图片） 
int newY = 0; 
// 截取比例（临时图片） 
double whPercent = 1; 
whPercent = ((double)iWidth / (double)iHeight) * ((double)srcImage.Height / (double)srcImage.Width); 
if (whPercent > 1) 
{ 
// 当前图片宽度对于要截取比例过大时 
newW = int.Parse(Math.Round(srcImage.Width / whPercent).ToString()); 
} 
else if (whPercent < 1) 
{ 
// 当前图片高度对于要截取比例过大时 
newH = int.Parse(Math.Round(srcImage.Height * whPercent).ToString()); 
} 
if (newW != srcImage.Width) 
{ 
// 宽度有变化时，调整开始截取的横坐标 
newX = Math.Abs(int.Parse(Math.Round(((double)srcImage.Width - newW) / 2).ToString())); 
} 
else if (newH == srcImage.Height) 
{ 
// 高度有变化时，调整开始截取的纵坐标 
newY = Math.Abs(int.Parse(Math.Round(((double)srcImage.Height - (double)newH) / 2).ToString())); 
} 
// 取得符合比例的临时文件 
Bitmap cutedImage = CutImage(srcImage, newX, newY, newW, newH); 
// 保存到的文件 
Bitmap b = new Bitmap(iWidth, iHeight); 
Graphics g = Graphics.FromImage(b); 
// 插值算法的质量 
g.InterpolationMode = InterpolationMode.Default; 
g.DrawImage(cutedImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, cutedImage.Width, cutedImage.Height), GraphicsUnit.Pixel); 
g.Dispose(); 
return b; 
} 
catch (Exception) 
{ 
return null; 
} 
} 

View Code 
/// <summary> 
/// jpeg图片压缩 
/// </summary> 
/// <param name="sFile"></param> 
/// <param name="outPath"></param> 
/// <param name="flag"></param> 
/// <returns></returns> 
public static bool GetPicThumbnail(string sFile, string outPath, int flag) 
{ 
System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile); 
ImageFormat tFormat = iSource.RawFormat; 
//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) 
{ 
iSource.Save(outPath, jpegICIinfo, ep);//dFile是压缩后的新路径 
} 
else 
{ 
iSource.Save(outPath, tFormat); 
} 
return true; 
} 
catch 
{ 
return false; 
} 
finally 
{ 
iSource.Dispose(); 
iSource.Dispose(); 
} 
} 

View Code 
/// <summary> 
/// 剪裁 -- 用GDI+ 
/// </summary> 
/// <param name="b">原始Bitmap</param> 
/// <param name="StartX">开始坐标X</param> 
/// <param name="StartY">开始坐标Y</param> 
/// <param name="iWidth">宽度</param> 
/// <param name="iHeight">高度</param> 
/// <returns>剪裁后的Bitmap</returns> 
public static Bitmap CutImage(Image b, int StartX, int StartY, int iWidth, int iHeight) 
{ 
if (b == null) 
{ 
return null; 
} 
int w = b.Width; 
int h = b.Height; 
if (StartX >= w || StartY >= h) 
{ 
// 开始截取坐标过大时，结束处理 
return null; 
} 
if (StartX + iWidth > w) 
{ 
// 宽度过大时只截取到最大大小 
iWidth = w - StartX; 
} 
if (StartY + iHeight > h) 
{ 
// 高度过大时只截取到最大大小 
iHeight = h - StartY; 
} 
try 
{ 
Bitmap bmpOut = new Bitmap(iWidth, iHeight); 
Graphics g = Graphics.FromImage(bmpOut); 
g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel); 
g.Dispose(); 
return bmpOut; 
} 
catch 
{ 
return null; 
} 
}