.net图片压缩的几种方法

方法一

private void button3_Click(object sender, EventArgs e)
{
using (OpenFileDialog ofd = new OpenFileDialog())
{
ofd.Filter = "图片|*.jpg;*.png;*.gif;*.jpeg;*.bmp";
if (ofd.ShowDialog() == DialogResult.OK)
{
using (FileStream file = new FileStream(ofd.FileName, FileMode.Open))
{
var img = CompressionImage(file, 50L);
MessageBox.Show(CreateImageFromBytes(AppDomain.CurrentDomain.BaseDirectory + @"" + Guid.NewGuid().ToString(), img));
}

}
}
}

/// <summary>
/// Convert Byte[] to Image
/// </summary>
/// <param name="buffer"></param>
/// <returns></returns>
public static Image BytesToImage(byte[] buffer)
{
MemoryStream ms = new MemoryStream(buffer);
Image image = System.Drawing.Image.FromStream(ms);
return image;
}

/// <summary>
/// Convert Byte[] to a picture and Store it in file
/// </summary>
/// <param name="fileName"></param>
/// <param name="buffer"></param>
/// <returns></returns>
public static string CreateImageFromBytes(string fileName, byte[] buffer)
{
string file = fileName;
Image image = BytesToImage(buffer);
ImageFormat format = image.RawFormat;
if (format.Equals(ImageFormat.Jpeg))
{
file += ".jpeg";
}
else if (format.Equals(ImageFormat.Png))
{
file += ".png";
}
else if (format.Equals(ImageFormat.Bmp))
{
file += ".bmp";
}
else if (format.Equals(ImageFormat.Gif))
{
file += ".gif";
}
else if (format.Equals(ImageFormat.Icon))
{
file += ".icon";
}
System.IO.FileInfo info = new System.IO.FileInfo(file);
System.IO.Directory.CreateDirectory(info.Directory.FullName);
File.WriteAllBytes(file, buffer);
return file;
}
/// <summary>
/// 壓縮圖片 /// </summary>
/// <param name="fileStream">圖片流</param>
/// <param name="quality">壓縮質量0-100之間 數值越大質量越高</param>
/// <returns></returns>
private byte[] CompressionImage(Stream fileStream, long quality)
{
using (System.Drawing.Image img = System.Drawing.Image.FromStream(fileStream))
{
using (Bitmap bitmap = new Bitmap(img))
{
ImageCodecInfo CodecInfo = GetEncoder(img.RawFormat);
System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
EncoderParameters myEncoderParameters = new EncoderParameters(1);
EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, quality);
myEncoderParameters.Param[0] = myEncoderParameter;
using (MemoryStream ms = new MemoryStream())
{
bitmap.Save(ms, CodecInfo, myEncoderParameters);
myEncoderParameters.Dispose();
myEncoderParameter.Dispose();
return ms.ToArray();
}
}
}
}

private static ImageCodecInfo GetEncoder(ImageFormat format)
{
ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
foreach (ImageCodecInfo codec in codecs)
{
if (codec.FormatID == format.Guid)
{ return codec; }
}
return null;
}

方法二

//string newImg = "images/MGoods/Detail_" + goods.ID + DateTime.Now.ToString("yyyyMMddHHmmssfff") + ext;
//Bitmap MyMap = new Bitmap(Server.MapPath(imgs.ImgUrl));
//if (!imghelper.GetPicThumbnail(path.TrimEnd('/') + imgs.ImgUrl, path + newImg, MyMap.Size.Height, MyMap.Size.Width, 1))
//{
// return Content("上传图片失败");
//}
//try
//{
// if (!string.IsNullOrEmpty(imgs.ImgUrl))
// {
// string delFile = Server.MapPath("~") + imgs.ImgUrl;
// System.IO.File.Delete(delFile);
// }
//}
//catch (Exception)
//{
//}

/// <summary>
/// 无损压缩图片 这样压缩后背景白色变为灰色？ 而且会截取一半主要是dHeight
/// </summary>
/// <param name="sFile">原图片</param>
/// <param name="dFile">压缩后保存位置</param>
/// <param name="dHeight">高度</param>
/// <param name="dWidth">宽度</param>
/// <param name="flag">压缩质量 1-100</param>
/// <returns></returns>
public static 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();

}
}