asp.net picture upload to generate thumbnails of attention _ practical skills

Bitmap. Save (Imgpath,imageformat.jpeg);
This is a piece of code to save the thumbnail, where the imageformat.jpeg must not be omitted, even if you save the file is JPG format, it can not be removed. Because if removed, the resulting thumbnail is larger than the original picture!


In addition, Imgpath must be created first, or it will produce a generic error for GDI +.
Path=system.web.httpcontext.current.server.mappath (path);
Use if (! System.IO.Directory.Exists (path)) System.IO.Directiory.CreateDirectory (path);


Generate thumbnails, do not use the Getthumbnailimage method, this method produces a thumbnail image quality is extremely poor, can not be used!



The simple code is as follows:
String Path=system.web.httpcontext.current.server.mappath (strpath);
Sourcepath=system.web.httpcontext.current.server.mappath (SourcePath);

if (! System.IO.Directory.Exists (path)) System.IO.Directory.CreateDirectory (path);

String Sourceimage =sourcepath + fileName;
String thumbimage = path + fileName;

Original artwork (reference)
Image Img=image.fromfile (sourceimage,true);

Actual thumbnail size
System.Drawing.Size size=pic.imgsize (maxw,maxh,img. Width,img. Height);
int w=size. Width;
int h=size. Height;

Drawing thumbnails
Bitmap bitmap=new Bitmap (w,h);
Graphics g=graphics.fromimage (bitmap);

Set thumbnail rendering quality
g.compositingquality=system.drawing.drawing2d.compositingquality.highquality;
g.smoothingmode=system.drawing.drawing2d.smoothingmode.highquality;
G.interpolationmode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

Clean background
G.clear (Color.White);

Rectangle thumbrect=new Rectangle (0,0,w,h);
G.drawimage (Img,thumbrect);

Save thumbnails
Bitmap. Save (Thumbimage,imageformat.jpeg);

Free memory
Bitmap. Dispose ();
Img. Dispose ();
G.dispose ();