在ASP.NET中实现图片上传，并按比例生成缩略图

private void btnUploadPicture_Click(object sender, System.EventArgs e)

{

//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

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 = 100; //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)

{

tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));

}

else

{

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();

}

}