C# 生成缩略图

/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="serverImagePath">图片地址</param>
/// <param name="thumbnailImagePath">缩略图地址</param>
/// <param name="width">图片宽度</param>
/// <param name="height">图片高度</param>
/// <param name="p"></param>
public void GetThumbnail(string serverImagePath, string thumbnailImagePath, int width, int height)
{
System.Drawing.Image serverImage = System.Drawing.Image.FromFile(serverImagePath);
//画板大小
int towidth = width;
int toheight = height;
//缩略图矩形框的像素点
int x = 0;
int y = 0;
int ow = serverImage.Width;
int oh = serverImage.Height;

if (ow > oh)
{
toheight = serverImage.Height * width / serverImage.Width;
}
else
{
towidth = serverImage.Width * height / serverImage.Height;
}
//新建一个bmp图片
System.Drawing.Image bm = new System.Drawing.Bitmap(width, height);
//新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bm);
//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
g.Clear(System.Drawing.Color.White);
//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(serverImage, new System.Drawing.Rectangle((width - towidth) / 2, (height - toheight) / 2, towidth, toheight),
0, 0, ow, oh,
System.Drawing.GraphicsUnit.Pixel);
try
{
//以jpg格式保存缩略图
bm.Save(thumbnailImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
serverImage.Dispose();
bm.Dispose();
g.Dispose();
}
}