Very Simple .NET Thumbnail Creation Code

re: Very Simple .NET Thumbnail Creation Code

Richard — Thu, 10 Jul 2008 21:17:19 GMT

Due to a "feature" of GDI+, calling Image.FromFile will keep the file locked until your process exits. If you're creating thumbnails from a long-running process (ASP.NET, Windows Service, etc.), you may want to use Image.FromStream instead:

using (Stream fs = File.OpenRead(s))

using (Image i = Image.FromStream(fs))

{

...

}

NB: You can't dispose of the stream until you've finished with the image:

http://support.microsoft.com/kb/814675

re: Very Simple .NET Thumbnail Creation Code

Omer van Kloeten — Thu, 10 Jul 2008 23:12:00 GMT

AFAIK, running GDI+ in an ASP.NET process is considered harmful and is unsupported by Microsoft.

re: Very Simple .NET Thumbnail Creation Code

Otto — Fri, 11 Jul 2008 00:23:02 GMT

If you use this on GIF or PNG images with transparency, what happens?

Very Simple .NET Thumbnail Creation Code

拝啓、サカモトと申します。 — Fri, 11 Jul 2008 01:43:33 GMT

Very Simple .NET Thumbnail Creation Code

re: Very Simple .NET Thumbnail Creation Code

John S. — Fri, 11 Jul 2008 08:27:57 GMT

GetThumbnailImage has a few issues. I highly recommend the method described here: http://www.glennjones.net/Post/799/Highqualitydynamicallyresizedimageswithnet.htm

In my opinion, the .NET image handling libraries are lacking some simple abstractions for consistent handling of jpg, gif (both transparent and not) and png resizing. It is way more complicated than it should be.

re: Very Simple .NET Thumbnail Creation Code

Mike — Fri, 11 Jul 2008 12:16:25 GMT

Also, be careful because if you don't specify an image encodig, it will just create a png. You might not notice, because when you open the file (test.jpg) it will display most of the time, but it could be an actual png file, and in some programs it might not open.

Seriously, posting these "this is simple, do it in 3 lines of code" articles are a bad idea hmmkay. Programming is not simple, and image processing is not simple either.

re: Very Simple .NET Thumbnail Creation Code

Eric — Fri, 11 Jul 2008 15:16:25 GMT

And why not use Directory.Delete(path, true) for recursive deletion of everything in the directory instead of coding a subroutine to do that?

re: Very Simple .NET Thumbnail Creation Code

mihailik — Fri, 11 Jul 2008 18:12:27 GMT

I can't believe you've forgotten to call Dispose!

re: Very Simple .NET Thumbnail Creation Code

Nathanael Jones — Sun, 10 Aug 2008 04:25:24 GMT

You can generate resized thumbnail versions on-the-fly with this module:

http://nathanaeljones.com/products/asp-net-image-resizer/

It's very stable, and includes disk caching for scalability.

You would just add ?thumbnail=jpg&maxwidth=160&maxheight=120 to the image path.