在ASP.NET中上传图片并生成缩略图

1、using System.Drawing;

2、protected void BtnLoadImage_Click(object sender, EventArgs e)
{
//UploadFile文件上传控件的ID.
//检查上传文件的格式是否有效
if(this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)
{
Response.Write("上传图片格式无效！"); return;
}
//生成原图
//获取上传文件的大小。
Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength];
System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream;
System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

int oWidth = oImage.Width;
//原图宽度
int oHeight = oImage.Height;
//原图高度
int tWidth =200;
//设置缩略图初始宽度
int tHeight = 100;
//设置缩略图初始高度
//按比例计算出缩略图的宽度和高度
if(oWidth >= oHeight)
{
//如果原图的宽度大于设置的宽度，用下列算法：原图高度*(设置的宽度/原图宽度).
tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));
}
else
{
//如果原图的宽度小于设置的宽度，用下列算法：原图宽度*(设置的高度/原图高度).
tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));
}
//生成缩略原图
Bitmap tImage = new Bitmap(tWidth,tHeight);
Graphics g = Graphics.FromImage(tImage);
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//设置高质量插值法
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//设置高质量,低速度呈现平滑程度
g.Clear(Color.Transparent);
//清空画布并以透明背景色填充
g.DrawImage(oImage,new Rectangle(0,0,tWidth,tHeight),new Rectangle(0,0,oWidth,oHeight),GraphicsUnit.Pixel);
string oFullName = Server.MapPath(".") + "/" + "o" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg";
//保存原图的物理路径
string tFullName = Server.MapPath(".") + "/" + "t" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg";
//保存缩略图的物理路径
try {
//以JPG格式保存图片
oImage.Save(oFullName,System.Drawing.Imaging.ImageFormat.Jpeg);
tImage.Save(tFullName,System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch(Exception ex)
{
throw ex;
}
finally
{
//释放资源
oImage.Dispose();
g.Dispose();
tImage.Dispose();
}

}