Alternatives to System.Drawing for use with ASP.NET?
After several days of tracking down bizarre GDI+ errors, I've stumbled across this little gem on MSDN:
Classes within the System.Drawing namespace are not supported for use within a Windows or ASP.NET service. Attempting to use these classes from within one of these application types may produce unexpected problems, such as diminished service performance and run-time exceptions.
I don't know whether "ASP.NET service" means "web application" in this context, but "diminished service performance" certainly seems to cover the random assortment of "A generic error occurred in GDI+" and "Out of memory" errors that my app is throwing - intermittent, non-reproducible errors reading and writing JPEG images that - in many cases - were actually created by System.Drawing.Imaging in the first place.
So - if GDI+ can't read and write JPEG files reliably in a Web app, what should I be using instead?
I want users to be able to upload images (JPEG required, other formats nice-to-have), resample them reliably, and display useful error messages if anything goes wrong. Any ideas? Are the System.Media namespaces from WPF worth considering?
EDIT: Yeah, I know GDI+ works "most of the time". That's not good enough, because when it fails, it does so in a way that's impossible to isolate or recover from gracefully. I am not interested in examples of GDI+ code that works for you: I am looking for alternative libraries to use for image processing.
Answer
There is an excellent blog post including C# code about using the ImageMagick graphics library through Interop over at TopTen Software Blog. This post deals specifically with running ASP.net on linux under mono; however, the C# code should be perfectly copy-paste-able, the only thing you'll need to change is the Interop attributes if you are running under windows referencing a window binary (DLL).
ImageMagick® is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats (over 100) including DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, and TIFF. Use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.
There is also an ImageMagick .Net development project on codeplex that wraps up everything for you. But it doesn't show active development since 2009, so it may be lagging behind the current ImageMagick library version. For a small trivial resizing routine, I'd probably stick with the interop. You just need to watch your implementation carefully for your own memory leak or unreleased resources (the library itself is well tested and vetted by the community).
The library is free and open source. The Apache 2 license appears to be compatible with both personal and commercial purposes. See ImageMagick License Page.
The library is totally cross platform and implements many powerful image handling and transformation routines that are not found in GDI+ (or not implemented under mono) and has a good reputation as an alternative for ASP.net image processing.
Update: Looks like there is an updated version of a .NET wrapper here: http://magick.codeplex.com/