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I have been having issues with the DownloadCompleted and DownloadFailed events failing to fire correctly from the BitmapImage object. This is a huge issue as the asynchronous processing of images is central to many types of WPF apps. Having events failing to fire correctly will likely have a rather large negative impact on these apps.

The problem is easily recreated. Iterate through any number of BitmapImage creations, subscribe to the DownloadCompleted and DownloadFailed events, and track the number of DownloadCompleted + DownloadFailed events which fire vs the number of events subscribed to. Those numbers should always add up.

In my testing the events only fire correctly on the first full iteration. After the first iteration they will never fire again. Ever. The event subscriptions are simply going into a black hole. Verify for yourself. You can create your own app or just use my test app.

I’d be interested to hear the results of everyones testing.

-MGE

The framework is coming along nicely. In the screenshots above you can see the before and after for my test image. The after image is composed of 800 photos pulled from flickr.

I’ve been focusing on the color matching algorithms, which I’m now pretty happy with. Although in the processed image you will notice that the halo around his head does not quite match, that is the result of settting a fairly high color tolorance of 20 rather than problems with color matching. Setting to a lower tolorance will result in closer matches (and also more difficulty in finding matches).

My next focus will be to improve rendering. For example, the overall look of the composite image will be a closer match if the same replacement image is not used more than once-or at least used only a very few times and not directly next to each other. Using the same images in succession results in too much of a pattern appearing in the image, as is the case with the processed image above. Less pattern is better. Think pointillism, like Matisse’s “La Maison verte, Venice” and you will have a good idea of what I’m striving for.

It’s interesting to note just how closely the composite will often match the original image. For example, the boy’s nose in the processed image is clearly visible. His ears and hair shading are distinct as well as the shadow under his chin. Some of the feather patterns on the left wing are even rendered…although in this case the wing pattern may be an example of the resuse of images working in favor of the composite image.

That’s it for now. More to come soon!

-MGE

Here is the updated source code for the PostItBoard WPF example app so that it compiles and runs on the latest NET 3.0 / WPF RC1. Or if you are only inerested in the binaries you can grab those too. In addition, apologies to everyone who asked me about the source code for the flickr assemblies that were missing from the previous release. This release has all the source code and projects.

Please drop me a line if you have any problems running this WPF example application.

Note: I get quite a few emails asking me if the image above is an actual screenshot of the application or if it was photoshopped. The image was in no way photoshopped. It is the application as it appears at runtime.

Cheers!

Michael G. Emmons

Click the image to run the WPF ScrollingCanvas example xbap or you can get the source code for it. This example creates a custom user control based on the Canvas container. This ScrollingCanvas allows you to scroll any FrameworkElement: text, video, shapes, or even whole scenes. Moreover, you can scroll multiple FrameworkElement objects at the same time in a single scroll container.Both speed and direction of the scroll is controllable via dependency properties. Simply drop the ScrollingCanvas control on the design surface or add it in XAML, add any FrameworkElements you want to scroll to the ScrollingCanvas container and call the ScrollBegin() method. All object scrolling is handled through local animations in the C# codebehind.

Greetings from Italy! I’m still on vacation enjoying Rome, so no new examples from me. However, Kevin Moore left a note indicating that the KevinButton source code, which my SmileyButton was based on, is now available from Kevin’s  Bag-o-Tricks RC1. It has a lot of cool stuff besides the KevinButton, so check it out! Head on over to Kevin’s Blog and peruse some screen shots of it.

 -MGE

Programmatically scrolling to a particular item in a ListView has become absurdly easy in WPF. However, it seems that this is not a well-known feature. I've had a number of people ask me about how to do this and if you google on "wpf ScrollIntoView" you will find almost nothing. All you need to do is get a reference to the item you are trying to scroll to and call the ScrollIntoView method, like so:

Easy, eh? To demonstrate the functionality, I've included this cheezy XBAP example...

Here are the project files for the SmileyButton WPF example. Enjoy!

 If you have any problems with this or any of my other WPF examples, drop me a line.

-Michael G. Emmons

Here is the XAML source code for the SmileyButton control templating xbap example which I showed in my previous post.

A few weeks ago there was a good humored Channel 9 video named "Reskin Your Application with the KevinButton". While the video is lighthearted, it makes a very important point: Control templates are one of the most powerful and important reasons why we should all look at WPF as our future development platform. I've had discussions with many people who are just starting to look seriously at WPF. Their initial response to the new platform is very similar and can be summed up by, "WPF has some cool features and nice eye-candy, but I don't find it particularly ground-breaking." Invariably these same people completely reconsider their initial impressions once they "get" what control templates are all about.

To get an understanding of exactly why control templates are so powerful you need to know that, with a very few exceptions, in WPF controls do not own their presentation. The presentation of a control is almost completely separated from the business logic of that control. By using a control template the presentation can be overridden to be almost anything.

In the Channel 9 video, Kevin Moore and Robby Ingebretsen create a new button template that animates a button using a grid, some rectangles and a few images. Check out the video. I was unable to find the source code for their example so I quickly created a similar SmileyButton xbap example for everyone to peruse. Just click on the picture below to run the xbap app. This does exactly the same thing as the KevinButton, but using different images. The smiley will animate according to which part of the button the mouse is over. This has been built using the July CTP.

If you haven't had a chance to watch the video, the important thing to note about this example is that the single control in the application is a button: it captures and hooks into all the events and methods that a standard button inherits. It just has its presentation changed to be something other than the default.

The xaml source code for this WPF example can be found in the next post.

I am currently looking at ideas for how text can be incorporated into an application in interesting ways by incorporating 3D surfaces. My proof-of-concept will be an xbap application which gives a hands-on review of the features of the Nokia N80 phone. My initial idea is to have a 3D representation of the phone which can be rotated. As the point-of-view of the phone changes documents related to the currently viewed face of the phone will rotate onto the viewing surface.

This is currently in the planning stages; I should have something to show in the next few days.

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