.NET 3.5

Converting and customizing XAML to PNG with server-side WPF

Laurent Bugnion — Thu, 09 Oct 2008 22:48:54 GMT

One Tweet by Oliver Sturm (http://twitter.com/olivers) the other day got me to thinking. He was asking about the possibility to host graphics for a web site in XAML format, and the best way to render it.

Currently, there are 3 possible ways that I know of to render XAML in a web browser

Loading the XAML file directly in an IFRAME will trigger Windows Presentation Foundation on the client (if available). The IFRAME can be positioned in the page so the it "blends" with the HTML page. That's only for Windows (IE and Firefox) and requires .NET 3.0 (or preferably 3.5/3.5 SP1) installed on the client. I wouldn't recommend that solution.
Silverlight can load loose XAML files. However, Silverlight XAML is less powerful than WPF XAML. Not all controls and features are supported. Also, it requires a plug-in to be installed on the client. The plug-in is available for a number of platforms, but still. More lightweight than solution 1, but still not ideal to render static images.
Rendering the XAML on the web server. This solution has the advantage to require installation of the .NET framework only on the web server (a controlled environment). WPF can render in memory, which is very convenient. No need for a visual, you can just load the XAML in a stream, and render as a bitmap image it in a memory stream, which in turn can be passed to the Response. Multiple bitmap formats are supported. In this example, we will use PNG.

I really want to write a more in-depth article about that, but for now I already post source code demonstrating 3 possible uses for this technique. To install the demo, follow the steps below.

Note: I am having some issues installing this on my web server, and trying to clear things up now. It works fine locally however.

Download the source code (Zip)
Unzip to a folder on your PC.
Open the Solution file in Visual Studio 2008. Note: This is targetting .NET 3.0.
Make sure that the web application "GalaSoft.Web.ConvertXamlToPng" is set as startup project.
Make sure that the file "index.html" is set as StartUp page.
Run the application by pressing Ctrl-F5.

The demo has 3 parts:

Localizing an image: In this sample, some strings are fetched from the resources (using a standard .NET resource manager) and set in the XAML scene after it has been loaded in memory. This solves a recurrent problem for web site managers: How can we design pictures in various languages without having to create (and store) one picture per supported language. In this demo, the same XAML file is localized in 3 different languages, and rendered to PNG.

Scaling an image: WPF and XAML are great for flow layout and element composition. Using tools like Expression Design and Expression Blend, it is easy to create compelling graphics that resize neatly. The second sample demonstrates this and allows the use to specify any size for an image. The XAML is loaded and rendered to that size directly on the server. Note that if you choose a very large size (thousands of pixels), the image appears pixellated. I am not sure yet what is the reason for it.

Customizing an image. In this last sample, you can parameterize multiple elements of the XAML scene. It's all a matter of finding the right element after the XAML has been loaded (FindName helps), finding the right DependencyPropertyand reflection are needed) and then setting the right object.

Just a word on the technology

One thing that WPF requires when it is being rendered (visually or in memory) is a STA (single threaded apartment). However, ASP.NET pages are typically rendered in MTA (multi threaded appatment). To solve this, you can either force an ASPX web page to run in STA (by using the <%@ ASPCOMPAT="true" %>directive in the Page) but that will degrade the performances. A much better way is to create a worker thread and to render the XAML in this thread.

One problem with that is that WPF is very particular with threads: To put it simply, a visual element created in a thread may not be used in another thread. We run into that problem when we parameterize the SolidColorBrush used by the last sample. In that sample, the replacement brush is created on the main thread, but used in the worker thread which creates an Exception. To avoid this issue, we "freeze" the SolidColorBrush after it is created. Frozen objects cannot be modified anymore, but they can be shared between threads.

What's missing?

Some things are still missing to this demo. I really would like to get it to work on my web server, but I am getting some issues. My understanding so far is that some assemblies are missing on the web server, which creates exceptions.

Another thing I would love to support is zoomability. Since XAML elements are vector graphics, and since ScaleTransform is supported, it is rather easy to add zoomability to an image. I experimented with that already and with good results, but it's not ripe for distribution yet. The problem here is that dimensions get all kind of wacky when you zoom an image (a 500 pixels wide image zoomed with a factor of 200% is suddenly 1000 pixels wide) and I am still looking for the best way to implement this in a generic way.

The XamlToPngConverter class

This is the main component used for the conversion. I won't write too much about it now, but it's implemented in a generic way, so that XAML can be loaded from any stream, and rendered to any stream. This allows for saving static images to a file, for example, rendering to a web response like here, etc... More details will follow.

I hope you like this demo and that it is useful. While it requires .NET 3.0 on the web server (and while it's not as straightforward on remote web servers as I was hoping for), it's a useful technique that I will be playing with more in the close future.

Microsoft to add jQuery in Visual Studio: Why I think it's great

Laurent Bugnion — Sun, 28 Sep 2008 22:44:28 GMT

The news took the community by surprise and the reactions are overwhelmingly positive: Microsoft is going to ship jQuery with the ASP.NET MVC framework (very soon) and with Visual Studio (in a near future). For more details, ScottGu and Scott Hanselman are talking about that in a very complete way.

I think it's great news on many levels. First, because I hear that jQuery is a great framework. I must admit I never used it, because I didn't do much web development lately (but I will get back to it in a number of private projects soon) and also because I am usually wary of frameworks and prefer to develop my own JavaScript. Of course this is only viable because I used JavaScript mainly on small private projects for the past few years, and I wanted to have the learning effect of programming against it directly instead of having a higher level framework to "talk to". I think that now is the time for me to look more into it, however, and this is just what I will do for my site www.galasoft.ch which needs a rather heavy facelift anyway.

But more importantly, it's a major step forward for Microsoft. There was a request for similar functionality in ASP.NET AJAX. This was on the list of requirements for a future version. And yet, instead of using the vast resources at their disposal, Microsoft decided to use an existing, widely acknowledged open source framework. They also plan to contribute patches to jQuery, but will do so following the standard procedure that this open source framework is already using.

This is really newsworthy because there are many other areas where such a decision could also be taken. I don't even want to talk about the Entity Framework vs NHibernate fiasco that so many others already dissected. But think about all the other areas: Testability immediately comes to mind...

Of course this also raises questions. Scott Koon already mentioned some of them, the one that I particularly appreciate being: "How will companies who are normally allergic to OSS code react to this [...]". After having worked for almost 13 years for Siemens, I know what he means. Every time we proposed an OSS technology, the question was always: Is that really safe. And I have to admit that, given the development timespan of some of our projects (typically 2 years between variant analysis and first release) and the lifespan of our products (typically more than 10 years and often much more than that), sometimes I have been careful with that too. See what happened to NDoc for example.

Still, there are so many other projects where OSS totally makes sense, and where Microsoft can save time and energy instead of reinventing the wheel. I am really glad to see that happening today, and think it's a great sign for Microsoft and for all .NET developers out there.

Silverlight 2 Release Candidate 0 for developers only

Laurent Bugnion — Fri, 26 Sep 2008 14:14:04 GMT

So many people blogged about it already (time difference, and fun dinner last night, so I am late :) that I prefer to just point the reader to the best possible source of information: Scott Guthrie's blog.

It cannot be stressed enough that this release is for developers only. It might very well be the last release before the final is made available, so it's a chance for people with Silverlight content to update their code. The public runtime will not be updated to RC0 automatically. So do *not* publish RC0 code to your web servers yet, because it will break the user experience!

I played with these bits quite a lot and they're really good. Many bugs have been fixed, and many corrections have been added to make it more compatible with WPF, which is really a must. Also added are some new controls (check Scott's blog for more details).

With that milestone, the Silverlight team did a really great job. The final version is getting closer and that's really exciting!

Silverlight 2 Unleashed: Table of Content

Laurent Bugnion — Sun, 14 Sep 2008 14:38:59 GMT

I am currently attending a workshop for Siemens in Chicago's suburb, and also staying for the weekend. In fact it feels pretty weird because for the first time since a year, I don't feel the pressure of "must write" on my shoulders, and I can actually spend some time thinking of something else than Silverlight 2 Unleashed... Which is why I am now writing a book about Silverlight 2 Unleashed (available on pre-order at Amazon and to be published really soon :)

I finished reviewing the very last chapters day on Friday and sent it to the editor. I still have one last round of review to just clean up some URLs, give a last look at the code and maybe find a typo or two... We're really close from the final version, and once this is done, the only occasion I will have to correct errors will be through errata on this blog, so stay posted. The book will also have a dedicated website at Sams, but I don't know the URL yet. I'll post it as soon as possible.

In the mean time, I posted the final table of content of the book in PDF format. Since the chapters are being laid out now, I don't have the page numbers yet, neither the page count (but it's probably going to be very similar to the WPF unleashed by Adam Nathan that many of you have, I am sure).

There has been a slight confusion on Amazon due to the fact that the book went from "Teach Yourself" to "Unleashed", but at least the cover and the price look right as well as the first part of the title. Our marketing guy (hey Curt!) is working on resolving this small issue.

It's pretty scary to let the work of a whole year go live, pretty much like what you feel when you have kids and they go to the playground alone for the first time, you know what I mean. I am terrified at the errors that I am sure that some of you will find :) and really if you do, I would love feedback (even negative) and will post corrections here if needed.

I'll be in Chicago until next Thursday and after that the next big trip will be PDC08. I am always interested in meeting new people so if you go too and want to say hello, drop a note here or (even better) on my Twitter feed at http://twitter.com/LBugnion. I am really excited about meeting again my client application development friends (I hear that many of the WPF Disciples will be there) and of course meeting new faces.

Sams Silverlight 2 Unleashed (was: Teach Yourself Silverlight in 24 Hours)

Laurent Bugnion — Mon, 01 Sep 2008 20:20:52 GMT

My editor at Sams (hey Neil :)) and I decided to convert the book I am almost done writing into an Unleashed. There are multiple reasons for that, the most important being that the book addresses multiple audiences, and has a broad range of coverage, which is typical of the Unleashed series. The content goes enough in depth (according to Neil) to be placed in the Unleashed series.

While the Unleashed series usually targets more advanced users than the Teach Yourself one, this book has lots of content that can be useful for a variety of
audiences with chapters that lead the user from the start of their journey through Silverlight. We put a great deal of attention in explaining complex concepts such as Object Oriented Programming, Data Binding, Templates, Transforms, the Animation system, Media integration, and so on with many practical descriptions, hands-on demos and figures which is typical of the books from Sams.

I was not too sure about that move at first, but after thinking about it I am pretty happy about it. Because Silverlight is such a new technology, Silverlight 2 Unleashed will maybe remind you of the famous WPF Unleashed by Adam Nathan, a book that was also published a very short time after WPF was released. And we all know that this book was a great success.

For those of you who already pre-ordered the book at Amazon, you should see the details about the new Unleashed book coming up soon. Sorry about any confusion caused, I am sure the change is for the best and I hope you'll love the book! I just checked the Amazon page and saw that they already updated the picture, but not the title yet, so don't get confused.

Oh, and since Amazon spilled the beans, I can now officially tell you that the book is in color. I won't start again the Petzold vs Nathan debate (sparkled by Jeff Atwood), but let's just say that I am really happy that the book is color coded. I think it makes understanding the code, especially for beginners, easier when it appears just as you see it in Visual Studio.

Preorder my Silverlight book on Amazon

Laurent Bugnion — Mon, 25 Aug 2008 22:24:31 GMT

Wow. That's an incredible feeling, seeing my name on Amazon :) The book is in pre-order!! I'd better get back to editing it then :)

Sams Teach Yourself Silverlight in 24 Hours, Table of Contents

Laurent Bugnion — Thu, 21 Aug 2008 13:38:59 GMT

I've been working since September 2007 (more or less) on an upcoming Silverlight book titled "Teach Yourself Silverlight in 24 Hours" at Sams. This book will be aimed at beginners with the technology (and maybe even beginners in programming). The reader is walked (with a lot of code samples and step-by-step examples) through most features of this amazing technology. The book has 24 chapters, each of them taking more or less (maybe rather a little more than a little less, to be honest :)) one hour to read. There are really tons of demos and cool examples, and so far the feedback I got has been really great.

Update: The book is now "SIlverlight 2 Unleashed". See the full Table of Content here.

Silverlight 2 beta 2 is live!

Laurent Bugnion — Sat, 07 Jun 2008 06:23:40 GMT

Here we go, Silverlight 2 beta 2 can be downloaded and installed! I had the chance to take part to an "insiders" program at Microsoft, and to play with SL2 b2 for a couple of weeks, and it's a good one. You should switch to b2 as soon as you can!

There are obviously incompatibilities between b1 and b2, but much, much less than between the alpha version and b1. We're getting there!!

Silverlight 2 beta 2 will be used to build applications related to the Beijing olympics, so it's going to be a real nature test for that version. As for the final release.... it's still very much hush hush, so let's leave it for now :)

The best place to start is ScottGu's blog. As usual, Scott describes the new features at length, and has links to all the places where you can download the good stuff.

Note that there is also a new version of Blend 2.5 which can be installed next to a "normal" Expression Blend V2. There is supposed to be a new version of Deep Zoom Composer too, but the download seems to be down currently.

Enjoy!!

Microsoft, you're kidding me, right??

Laurent Bugnion — Thu, 05 Jun 2008 17:48:48 GMT

You got to be kidding me. What if I want Expression in the US locale, I can't buy it just because my IP is not in the US? Honestly? You are *that* stupid?

My talk at the "Internet Briefing RIA conference" in Zurich

Laurent Bugnion — Thu, 29 May 2008 21:11:28 GMT

I just posted today's talk at the RIA conference in the World Trade Center, Zurich. Unfortunately it was not recorded, but the slides and the demos' source code is available on my site.

The talk went really good, even though the crowd was rather tough :) Trying to "sell" Windows Presentation Foundation, a desktop Windows-only technology, to an audience of web developers, many of them using Java and open source technologies (and even one Adobe employee) sparkled some very interesting discussions. I can't say I convinced everyone (and it was most certainly not my intention), but I think everybody had a really good time. I know for sure that I did!

To all those who stayed until the end of my presentation, and even though mine was the last presentation of the day, thank you very much!! To those who couldn't stay, I hope you'll have fun checking the slides and the demos, and contact me if anything is unclear!!