话不多说，请看代码：
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/// <summary>
/// 根据指定尺寸得到按比例缩放的尺寸,返回true表示以更改尺寸
/// </summary>
/// <param name="picWidth">图片宽度</param>
/// <param name="picHeight">图片高度</param>
/// <param name="specifiedWidth">指定宽度</param>
/// /// <param name="specifiedHeight">指定高度</param>
/// <returns>返回true表示以更改尺寸</returns>
private bool GetPicZoomSize(ref int picWidth, ref int picHeight, int specifiedWidth, int specifiedHeight)
{
int sW = 0, sH = 0;
Boolean isZoomSize = false;
//按比例缩放
Size tem_size = new Size(picWidth, picHeight);
if (tem_size.Width > specifiedWidth || tem_size.Height > specifiedHeight) //将**改成c#中的或者操作符号
{
if ((tem_size.Width * specifiedHeight) > (tem_size.Height * specifiedWidth))
{
sW = specifiedWidth;
sH = (specifiedWidth * tem_size.Height) / tem_size.Width;
}
else
{
sH = specifiedHeight;
sW = (tem_size.Width * specifiedHeight) / tem_size.Height;
}
isZoomSize = true;
}
else
{
sW = tem_size.Width;
sH = tem_size.Height;
}
picHeight = sH;
picWidth = sW;
return isZoomSize;
}
/// <summary>
/// 无损压缩图片
/// </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 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 = iSource.Width, sH = iSource.Height;
GetPicZoomSize(ref sW, ref sH, dWidth, dHeight);
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();
}
}
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以上就是本文的全部内容，希望本文的内容对大家的学习或者工作能带来一定的帮助，同时也希望多多支持服务器之家！
原文链接：http://www.cnblogs.com/tpfOfBlog/archive/2017/04/12/6700431.html