不多说了，直接看代码：
/// <summary>
/// 缩略图
/// </summary>
/// <param name="imgurl">大图片路径</param>
/// <param name="thumbnailPath">小图片路径</param>
public static void MakeThumbnail(string imgurl, string thumbnailPath)
{
int width = 100;//缩略图照片宽度
int height = 62;//缩略图照片高度
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(imgurl);
int towidth = 0;
int toheight = 0;
if (originalImage.Width > width && originalImage.Height < height)
{
towidth = width;
toheight = originalImage.Height;
}
if (originalImage.Width < width && originalImage.Height > height)
{
towidth = originalImage.Width;
toheight = height;
}
if (originalImage.Width > width && originalImage.Height > height)
{
towidth = width;
toheight = height;
}
if (originalImage.Width < width && originalImage.Height < height)
{
towidth = originalImage.Width;
toheight = originalImage.Height;
}
int x = 0;//左上角的x座标
int y = 0;//左上角的y座标
//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//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(Color.Transparent);
//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, x, y, towidth, toheight);
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}