Version 2.1b released!

Better performance, better installation, better samples, more features!


  • I finally tracked down a simple, yet elusive performance bug  that was particularly problematic for users with many thousands of images. Performance should be much better for everyone now, so upgrading is highly suggested.  This bug was introduced with version 2.0., and caused a filesystem listing hit for each request.
  • All requests are now forced to pass through the UrlAuthorizationModule now. Previously, any URL rewriting (like customfolders.cs) caused URL auth rules to be circumvented. This was documented behavior, but a secure solution has now been found.


  • New users will find it much easier to get things working - Messing with IIS is now completely optional! :D :D Instead of writing  "image.jpg?width=500" as you normally would, type "image.jpg.axd?width=500". If you use the new syntax, you won't be forced to configure wildcard mapping on IIS6/IIS7 classic. Both syntaxes will be supported in the future. The suggested extension is .axd, but that can be changed or disabled using the ResizeExtension application setting.
  • Dithering support added! You can dither an 8-bit image using the ?dither= command. You can specify a dither percent, "true", or "4pass".
  • UploadSample  project (in VB). Resizing images as they are uploaded is now trivally easy. ImageManager.BuildImage now accepts an HttpPostedFile instance for resizing.
  • DisableCustomQuantization setting to allow GIFs to be generated on servers where the Marshal class is prohibited.
  • PerfTests project to run benchmarks on the image resizing and encoding code.

Upgrade proccess

  1. Replace the old files with the new files from the ImageResizer folder. If you are using the .DLL, replace the DLL in the bin folder. Keep your old CustomFolders.cs and WatermarkSettings.cs files if you have modified them.
  2. Delete the /imagecache directory.
  3. Insert/change the following application settings in web.config if you want to use the new syntax.
<add key="ResizeExtension" value=".axd"/>
<add key="AllowURLRewriting" value="true"/>
If you are upgrading from 1.2, follow the 1.2->2.0 upgrade instructions first.

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About Nathanael

Nathanael Jones is a software engineer, father, consultant, and computer linguist with unreasonably high expectations of inanimate objects. He refines .NET, ruby, and javascript libraries full-time at Imazen, but can often be found on stack overflow or participating in W3C community groups.


If you develop websites, and those websites have images, ImageResizer can make your life much eaiser. Find out more at


I run Imazen, a tiny software company that specializes in web-based image processing and other difficult engineering problems. I spend most of my time writing image-processing code in C#, web apps in Ruby, and documentation in Markdown. Check out some of my current projects.

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