14. September 2010
Recently I have been working on a tile serving utility that would generate tiles on the fly but also cache them at the same time for future usage. After releasing our map tiling tool for manifold this was the next step.
The tile rendering functions were working nicely and the process was fairly quick so enabling data caching functionality could only speed things up ;-) So far so good... It was supposed to be just a matter of saving the output bitmap to a file... So I did it the way I usually do and tried to save my tile this way:
Apparently this was throwing an error. A very descriptive one: A generic error occurred in GDI+... Not very helpful, is it?
After googling for a while it looked like this was supposed to be a permissions problem but allowing my IUSR to write to the specified folder did not help at all. What's worse I have found some info on the msdn that one should avoid using the System.Drawing namespace in ASP.NET: 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.
Another solution I found on the web was to clone the bitmap in question and then save it, though that gave the same error. No avail in my case.
Luckily after messing with the problem a bit more I have discovered that writing a bitmap to a memory stream and then saving the data using Sytem.IO.File.WriteAllBytes did the trick:
System.IO.MemoryStream outStream = new System.IO.MemoryStream();