C#圖片無損壓縮

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/// 使用方法：本方法由於內部統一設定dHeight，dWidth和原圖片的長寬一致，所以圖片的大小一樣。
/// flag:壓縮率，這裡僅僅壓縮像素，不改變圖片的外觀大小（既長寬）
/// 無損壓縮圖片
/// <param name="sFile">原圖片</param>
/// <param name="dFile">壓縮後儲存位置</param>
/// <param name="dHeight">高度</param>
/// <param name="dWidth"></param>
/// <param name="flag">壓縮品質(數字越小壓縮率越高) 1-100</param>
/// <returns></returns>

public static bool GetPicThumbnail(Stream sFile, string dFile, int dHeight, int dWidth, int flag)
{
Image iSource = Image.FromStream(sFile);
ImageFormat tFormat = iSource.RawFormat;
int sW = 0, sH = 0;

//如果需要調節圖片的長寬大小需要注釋下面兩行代碼
dHeight = iSource.Height;
dWidth = iSource.Width;
//按比例縮放
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 = 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();
//以下代碼為儲存圖片時，設定壓縮品質
EncoderParameters ep = new EncoderParameters();
long[] qy = new long[1];
qy[0] = flag;//設定壓縮的比例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是壓縮後的新路徑
}
else
{
ob.Save(dFile, tFormat);
}
return true;
}
catch
{
return false;
}
finally
{
iSource.Dispose();
ob.Dispose();
}

C#圖片無損壓縮