DeflateStream in Silverlight

Another circumvented area in the Silverlight core libraries is compression and decompression of streams. The entire System.IO.Compression namespace that can be found in the regular .NET Framework is missing in Silverlight.

But of course, this limitation has been recognized. In the dotnetzip project on Codeplex, there is a Silverlight branch that among other things provide a DeflateStream replacement. This was a very welcome finding in my efforts of adapting as much as possible of the mdcm C# DICOM library to Silverlight.

My thanks go to the Codeplex user cheeso for this contribution!

WriteableBitmap extensions in Silverlight

The Silverlight WriteableBitmap class, intended for user-defined bitmap design, has very limited functionality by itself. It really only provides the Pixels property for direct modification of the editable bitmap.

Fortunately, this limitation has been recognized and mitigated by René Schule. René has initiated WriteableBitmapEx, which is a library of extension methods for the WriteableBitmap class. The entire project is open source (Microsoft Public License) and can be found on Codeplex.

I most urgently needed methods for rotation and flipping of the bitmap image, but there are also various methods for cropping, resizing, individual pixel editing, drawing shapes on the bitmap etc. All in all some very helpful extension methods for this specific need.

Parallel operations in Silverlight

As far as I have been able to find out, Silverlight is fairly limited with respect to parallel and/or multithreaded computation support. The Parallel framework from .NET 4.0 is for example not present at all. However, it seems like the ThreadPool is a reasonable candidate for doing at least some work in parallel.

Based on the MSDN documentation for Silverlight, I have composed a very simple code snippet for separating larger computational work onto for example all available CPU cores.

int threads = Environment.ProcessorCount;

WaitHandle[] handles = new WaitHandle[threads];

for (int i = 0; i < threads; ++i)

{

handles[i] = new ManualResetEvent(false);

ThreadPool.QueueUserWorkItem(

delegate(object state)

{

...some long-running thread-able process...

((ManualResetEvent)state).Set();

}, handles[i]);

}

WaitHandle.WaitAll(handles);

I tested the above snippet on my eight CPU core computer, and repeated the same process throughout all iterations. The above parallel approach was then 2.5 times faster than the purely sequential one. Not a very impressive result, of course. There is certainly room for improvements, hopefully I will be able to implement more impressive speed-ups in due time.

DICOM and WPF

I have recently taken up the effort of adapting the C# DICOM class library mdcm to Silverlight, as can be seen on the forked project website at Github.

Initially, I excluded all imaging, codec, HL7 and network functionality in order to make the library build at all in Silverlight.

Just now I have begun looking at porting the mdcm image handling to Silverlight. The mdcm library uses the .NET System.Drawing library for image handling, which is not available in Silverlight. However, I have modified the source code so that when it compiles for Silverlight, it instead uses the BitmapSource and WriteableBitmap classes from the System.Windows.Media.Imaging namespace.

The added benefit of these modifications are that they are equally applicable to WPF, i.e. it would be a simple task to switch from Windows Forms (which the original mdcm library depends upon) to WPF, given these Silverlight motivated modifications.

I have not explicitly made any WPF adaptation yet, but this is clearly worth future exploration.

UPDATE AUG 21: WPF support is now implemented! Please have a look in the Github repository and this blog post.

Advanced calculations for the web!

In my efforts to bring further functionality to the web, I have today explored the possibility of porting the versatile Meta.Numerics class library to Silverlight. Luckily enough, this was quite an easy task.

I only had to omit serialization support via the Serializable attribute, and the ADO.NET coupling of the various statistical Sample classes, otherwise the Silverlight class library built without issues.

The Meta.Numerics class library is distributed under the Microsoft Public License. I soon hope to find a suitable way for making the Silverlight library modifications public, either via Github or CodePlex.

DICOM and Silverlight

Since I would like to provide DICOM functionality in a Silverlight environment, I have examined whether there are any obvious libraries or tools available that would facilitate. Leadtools provide a DICOM Silverlight software development kit as a component in some of their commercial products, but so far I have not been able to identify any open source DICOM toolkit for Silverlight.

I have been using Colby Dillion's C# DICOM library mdcm for a while. This library provides all the DICOM functionality I have had the need for, but it has only been available for desktop applications until now.

However, I have started exploring whether the mdcm library can be sufficiently migrated to Silverlight. My continuous efforts can be followed here. At this stage I have made all shortcuts necessary to make the Silverlight class library build at all, and I have only included the most central parts of the original library. In due time I will fine tune the shortcuts to mimic the original library as much as possible, and I will try to add as many missing parts as I can.

It will be exciting to see if this effort can eventually result in a true open source alternative for DICOM functionality in Silverlight!

Units of Measure in C#: Introduction

F# provides the feature Units of Measure for sufficiently handling measurable entities of different units and quantities. Unfortunately this functionality is not accessible from the other .NET languages.

I have searched the internet for a similar solution in C#, but the approaches I have found so far have been relatively heavy-weight and not easily extendable. In particular, the measure type is generally implemented as a class with several members.

I would prefer a more light-weight solution where the measure type is implemented as a struct, preferably with a single member representing the measured amount in some reference unit for each specific quantity. At the same time I would like to have quantity type safety during compile-time, and it should the library should be easily extendable with new quantities and units without affecting the implementation of the measure type.

Based on these requirements, I have now implemented a compact C# Units of Measure library. I have implemented the library using the .NET 3.5 profile, and I have verified that it is possible to build under Mono (2.8 or later) as well. As far as I can tell, there is nothing preventing use of this library from other .NET languages either.

To facilitate feedback from other developers with similar requests, I have made the library available as open source (under the Eclipse Public License). The library is denoted csunits and is available on Github. A quick introduction to the API and instructions for extending the library are also provided on this web site.

I plan to continuously extend the library with new quantities and units, as well as add more functionality to it. In particular, I plan to implement a measure array type for efficient numerical handling of large number of measures in the same unit.

Any feedback on the library is more than welcome. Issues are preferably reported on the Github project web site, but comments to this blog post are perfectly OK as well :-) And ideas on how to further extend the library are of course very much appreciated.