Stefan Wick's Weblog - Development with Silverlight, WPF and Tablet PC : Silverlight Samples

Silverlight 3 Beta: Perspective 3D

swick — Wed, 18 Mar 2009 10:24:00 GMT

Silverlight 3 Beta has been released today. This release includes a number of exciting new features that I want to illustrate with a series of quick samples on my blog. (more info on Silverlight 3 Beta and how to get the bits and tools).

The first new feature I want to show is Perspective 3D transformation. We have added a powerful new property 'Projection' to UIElement that lets you rotate and move any element in your tree in 3D space! The usage is very simple, no complicated math required - just set the Projection property to a PlaneProjection in XAML or code and specify how you want to rotate or move your elements. You can then change these properties dynamically at runtime, either through code or animations.

<Grid >

<Grid.Projection>

</Grid.Projection>

</Grid>

(More info on Perspective 3D in Silverlight 3 Beta)

Below is a live example of this new feature in action. The source is attached to this post. Note that you need the Silverlight 3 Beta Tools for VS in order to build the project. To view the live sample on this page you just need the Silverlight 3 Beta runtime installed. In the sample I have two surfaces back-to-back to each other, simulating a postcard in 3D space. Use the sliders to rotate the postcard around x, y or z axis. To demonstrate that the projected visuals are actually live and also take input, I have ink-enabled then, so you can draw on either side of the postcard.

The below sample has been update for the Silverlight 3 RTW Runtime (download)

Custom Ink Rendering in Silverlight 2

swick — Tue, 02 Dec 2008 00:26:00 GMT

Drawing ink with the built-in stroke objects works great for handwriting and annotations. In some scenarios, however, you may want something more fancy that takes advantage of Silverlight's rich graphics capabilities.

Creating ink strokes with a customized appearance is fairly straight forward with Silverlight 2. You basically collect StylusPoints in mouse events as usual, but instead of adding them to stroke objects, you just draw your own geometries or shapes at the stylus/mouse location.

When collecting sample points during the MouseMove event, please be sure to call the StylusDevice.GetStylusPoints() method and process all points returned from that call. This will ensure that stylus users will get the full fidelity of input points, since their pointing device reports points more often than the MouseMove events fires. Also it is good practice to interpolate points between sample points, since they won't usually be equidistant.

I have a attached a sample project that demonstrates the concept end-to-end using Ellipse shapes with a LinearGradientBrush to give my ink strokes a custom look. Below is live version of the sample for you to play with.

Erasing Ink in Silverlight 2

swick — Sun, 30 Nov 2008 18:09:00 GMT

Another frequently asked question around inking in Silverlight is about erasing Ink strokes after they have been collected or loaded. Unlike WPF or the Tablet SDK for COM & Winforms, Silverlight does not come with controls that have built-in eraser modes in the box. However, with a little bit of code-behind you can implement those modes and adjust them to your specific needs. The key APIs you will need for this are StrokeCollection.HitTest() and Stroke.HitTest(). Both APIs take a collection of StylusPoints as input and they return a value indicating whether or not the ink stroke(s) have been hit. Based on that you can then modify your collection accordingly to represent the result of the erase operation. Popular inking apps (e.g. Windows Journal) offer two different modes of erasing:

Erase By Stroke:
Implementing this mode is fairly straight forward. Just pass the stylus points collected along the eraser path into the HitTest() method of your collection of ink strokes and the API will tell you which strokes to remove from your collection.

Erase By Point:
This one takes a little more effort to get right. We start like above, but then we don't remove the hit strokes. Instead, we figure out which segment of the stroke was hit (by using the Stroke.HitTest() API) and then we split the stroke by removing that segment.

I have attached a sample that implements both modes. You can also check out a live version of the sample below. The simplistic implementation of "Erase By Point" in the sample leaves some areas of improvements for the reader (or for a future blog post). Most notably, the size the chunk erased in this mode is not very consistent as it depends on several factors (distance points, location of the hit point, thickness of the stroke, etc.). A good improvement would be to add some logic that ensures the eraser always cuts a consistent chunk out of the ink strokes.

Saving Ink to IsolatedStorage with Silverlight 2

swick — Sat, 01 Nov 2008 21:38:00 GMT

One of the questions I have seen quite a few times in the Silverlight.net forums is how to persists (and de-persists) ink in Silverlight 2. Unlike WPF, Silverlight does not support a binary persistence format (ISF), but you can write some code to save and load ink to and from XAML. To demonstrate how to do this in a real world example, I am using another very cool feature in Silverlight 2: IsolatedStorage

IsolatedStorage is a per application, per computer, per user storage that offers a powerful, easy to use way for your web applications to store data locally on the user's and retrieve it later when the user visits your sites again on the same computer. You can use it like a file system, or as in the case of this example, simply use it to store application settings in key/value pairs. Learn more about how to do the latter here.

The goal of my application is to store the ink as XAML in IsolatedStorage when the user navigates away from the site. Upon return, the app will retrieve the persisted data from the storage, depersist it and present the ink to the user. Here are the relevant pieces of code (full code project is attached to this post).

Serializing and de-serializing ink strokes using XAML:

public string InkXAML

{

get

{

// persists ink strokes to XAML

StringBuilder builder = new StringBuilder();

XmlWriter writer = XmlWriter.Create(builder);

writer.WriteStartElement("StrokeCollection",

"http://schemas.microsoft.com/winfx/2006/xaml/presentation");

foreach (Stroke stroke in _presenter.Strokes)

{

writer.WriteStartElement("Stroke");

writer.WriteStartElement("Stroke.DrawingAttributes");

writer.WriteStartElement("DrawingAttributes");

writer.WriteAttributeString("Width",

stroke.DrawingAttributes.Width.ToString(invCult));

writer.WriteAttributeString("Height",

stroke.DrawingAttributes.Height.ToString(invCult));

writer.WriteAttributeString("Color",

string.Format(invCult, "#{0:X2}{1:X2}{2:X2}{3:X2}",

stroke.DrawingAttributes.Color.A,

stroke.DrawingAttributes.Color.R,

stroke.DrawingAttributes.Color.G,

stroke.DrawingAttributes.Color.B));

writer.WriteAttributeString("OutlineColor",

string.Format(invCult, "#{0:X2}{1:X2}{2:X2}{3:X2}",

stroke.DrawingAttributes.OutlineColor.A,

stroke.DrawingAttributes.OutlineColor.R,

stroke.DrawingAttributes.OutlineColor.G,

stroke.DrawingAttributes.OutlineColor.B));

writer.WriteEndElement();

writer.WriteStartElement("Stroke.StylusPoints");

writer.WriteStartElement("StylusPointCollection");

foreach (StylusPoint sp in stroke.StylusPoints)

{

writer.WriteStartElement("StylusPoint");

writer.WriteAttributeString("X", sp.X.ToString(invCult));

writer.WriteAttributeString("Y", sp.Y.ToString(invCult));

writer.WriteEndElement();

}

writer.WriteEndElement();

}

writer.WriteEndElement();

writer.Flush();

return builder.ToString();

}

set

{

// depersist ink strokes from XAML

try

{

_presenter.Strokes = XamlReader.Load(value) as StrokeCollection;

}

catch (Exception exc) { Debug.WriteLine(exc.ToString()); }

}

Persisting data on Application exit:

void Application_Exit(object sender, EventArgs e)

{

IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;

string inkXAML = _inkCollector.InkXAML;

if (settings.Contains("Ink"))

{

settings["Ink"] = inkXAML;

}

else

{

settings.Add("Ink", inkXAML);

}

Loading data on Application startup:

public Page()

{

InitializeComponent();

_inkCollector = new InkCollector(inkNote);

IsolatedStorageSettings settings =

IsolatedStorageSettings.ApplicationSettings;

string inkXAML = "";

if (settings.Contains("Ink"))

{

inkXAML = settings["Ink"] as string;

_inkCollector.InkXAML = inkXAML;

}

If you have Silverlight 2 installed (who hasn't? :-)), you can try it out live below. Draw some ink, navigate away, close the browser, clear the cache, etc. Then return to my blog and see that your ink is back, due to the power of IsolatedStorage.

Silverlight 2 Released - Write On!

swick — Tue, 14 Oct 2008 08:45:00 GMT

Now that Silverlight 2 is released, I finally got around to updating my blog after a long time of silence. For those of you interested in handwriting and Tablet related technologies, I want to start out with a canonical example of a Silverlight 2 Inking application. There have been a couple of OM changes since Beta1 around ink and stylus in Silverlight, mostly in order to make the Silverlight API more consistent with the WPF Ink/Stylus APIs.

Just like in Silverlight 1.0, the key element to inking is the InkPresenter which is a Canvas-like element with the ability to render ink strokes. To bring it to live and actually enable ink collection (and eraser) funtionality you will need to write some code-behind that responds to the user's input. In my example I have encapsulated the required code into a re-usable 'InkCollector' class (in InkCollector.cs), so you can just instantiate and assign it to your InkPresenter in order to get started with inking in your own projects.

Here is my example - source code attached - try it out by using your mouse or stylus to write and erase ink:

Snipping Pictures with Silverlight

swick — Tue, 18 Dec 2007 20:45:00 GMT

One of my favorite tools on the Tablet PC is the 'Snipping Tool'. I have been using it frequently since the early XP days (back then we shipped it seperately as a Power Toy). Now in Vista, it's part of the main OS and I find myself using it quite often event on my desktop PC.

When I was using the tool recently, I got this idea for a new Silverlight sample app: wouldn't it be cool to snip pieces from various images and put them together as a collage in Silverlight - and then annotate the result with text, drawings and/or handwriting?

Silverlight's imaging and ink APIs make this fairly easy. Here are my results of this effort using Silverlight v1.0 - the sample demonstrates these features:

Select an image from an animated collection of pictures
Snip a piece of the selected image (free-form, rectangle or entire picture) and arrange it on the canvas
Use 'Image Tools' to control zoom, rotation and opacity of individual snippets
Use 'Text Tools' to add/change text annotations
Use 'Ink Tools' to add/change drawings and handwritten annotations
Full screen and embedded mode

Couple of notes and caveats:

The pictures are currently hardcoded (appropriate for the holiday season :-) ), but you can easily change that in the attached source code to use your own pictures or to pull images from the web.
When you launch the app from this blog, it opens up in full screen mode (since this is the best mode to view and use it). You can press the 'Esc' key or use the 'Miscellaneous' menu to go back to embedded mode.
In full screen mode Silverlight disables keyboard input (for security reasons). So if you want to enter some text annotations, please switch to embedded mode.
The 'Create Bitmap' button doesn't do anything in this version. The idea is to invoke some server-side code here to generate a bitmap of your collage. If there is interest in the community, this might be a good topic for a seperate blog post. But then again: if you are on Windows Vista, you can just use the Snipping Tool in the OS, to grab your collage and save it as bitmap :-)

The sample's complete source code is attached to this post. A live version, hosted via Silverlight Streaming, is included below for you try out. Click the button to launch the app:

Ink Reflections - in Silverlight

swick — Sun, 02 Dec 2007 08:25:00 GMT

I have received several question from folks about my earlier post on Ink Reflections in WPF. People were curious how to accomplish the same or a similar effect in Silverlight, in the absence of the VisualBrush object.

Clearly, WPF's VisualBrush is the main object that enables scenarios like this and it definitely makes their implementation straightforward. However, in Silverlight you can also accomplish effects like this with little bit of extra coding.

First of all, Silverlight has an ImageBrush and a VideoBrush, so as long as the visul you want to mirror is an image or a video, you can apply the same technique as used in my WPF sample and you are done.

If you want to mirror a different type of visual, you will have to manage the mirror yourself, meaning you have to create a secondary, mirrored visual and update it whenever the original changes.

I have created a sample that demonstrates both techniques together. The yellow background with silver border is an image that gets mirrored using an ImageBrush. The ink you draw (and erase) gets mirrored programmatically using some JavaScript code-behind.

The sample's source code is attached. A live version, hosted via Silverlight Streaming, is included below for you try out.

Annotating Video with Ink using Silverlight

swick — Thu, 15 Nov 2007 16:44:00 GMT

Silverlight makes delivering video content in the browser very easy. Silverlight also has ink support built-in. So why not combine these two features to enable some great new scenarios?

I have put together a little sample using Silverlight v1.0 to record and play back ink annotations, synchronized with the video playback. Below is the key piece of XAML markup for this application. We are using an InkPresenter that hosts the MediaElement with the video and takes care of the ink renderering. Also note the empty storyboard here as this is the magic sauce for the synchronized ink playback.

<InkPresenter Name='inkPresenter' Canvas.Left='10' Canvas.Top='10'

MouseLeftButtonDown='onInkPresenterDown'

MouseMove='onInkPresenterMove'

MouseLeftButtonUp='onInkPresenterUp'>

<InkPresenter.Resources>

<Storyboard Duration="0:0:0" Completed="onStrokePlaybackTimerTick"

x:Name="strokePlaybackTimer" />

</InkPresenter.Resources>

<MediaElement Name='mediaElement' Source='bear.wmv'

Width='720' Height='480'

AutoPlay='False' MediaEnded='onMediaEnded'/>

</InkPresenter>

The relevant pieces in the JavaScript code behind the XAML (in file events.js), are the following functions:

ConvertInkToString(strokes) - a function to serialize the point data for the ink strokes into a string for persistence purposes
ConvertStringToInk(serializedStylusPoints) - the reverse function that returns a StrokeCollection for a serialized ink string
onStrokePlaybackTimerTick() - during playback this function is called on every frame; when it is time to play back a stroke, we do so point by point

The full source code is attached to this post. I have also uploaded the sample to the Silverlight Streaming service, so I can pull it directly into my blog here. To check it out, just click the button below to load the sample. Once the video is loaded, you can click the 'Playback' button to replay my pre-recorded ink annotation - or you can click 'Start Recording' to record your own annotations, and then play them back afterwards.

Ink blogging - using Windows Journal and Silverlight Streaming!

swick — Sun, 04 Nov 2007 21:56:00 GMT

Are you using Windows Journal to jot down your thoughts on your Tablet PC? Did you ever wish to publish your handwritten notes to your blog?

Here is one way to do this: The TabletPC SDK provides a Journal Reader API that provides access to the content of the .jnt file. Now you can read all content and convert it into a 'blog-friendly' format. Since Silverlight offers great ways to present content in an attractive, interactive way, I decided to write a Journal -> Silverlight converter. The result of this test project is now available as SDK sample on microsoft.com/downloads.

The converter is easy enough to use. Just drop down to a command box and run "JntToSilverlight.exe MyNotes.jnt". This will produce a 'MyNotes' folder that contains the resulting Silverlight application. You can test the results now by double-clicking the 'default.htm' file to load the app into your browser.

OK, now how do I get all this onto my blog? Using Silverlight Streaming, it's very easy: just zip it up, upload it to the service and then stick an IFrame into your blog's HTML. See my previous post on this subject.

To summarize the steps:

1) Create a note in Windows Journal

2) Convert note to Silverlight app

3) Upload to Silverlight Streaming service

4) Insert IFrame into blog

This is still a lot of steps and a bit tedious, but it's a proof of concept. Steps 2-4 all have an API they so are automatable and one could create a tool that does all that in one step.

Here is one example of a converted note on my blog (the original .jnt is attached to this post, if you want to compare). Besides flipping through the pages, you can add more ink, move selected content around and erase ink. Also don't miss the full-screen mode and the mouse-wheel zoom feature!

Silverlight Ink SDK Sample - hosted through Silverlight Streaming

swick — Sat, 03 Nov 2007 16:40:00 GMT

With the 'Silverlight Streaming' service you can now invoke a hosted Silverlight application using an IFrame - without any JavaScript! This allows you to embed Silverlight content on sites that do not allow adding JavaScript, as long as they support IFrames. For details refer to this MSDN topic.

To demonstrate this great service, I have taken the Silverlight Ink SDK Sample, uploaded it to Silverlight Streaming and then embedded it on this blog using an IFrame, like this:

The highligthed part is the key: it specifies your Silverlight Streaming application ID and name of your app. For more information about Microsoft Silverlight Streaming, visit http://silverlight.live.com/.

Here is the sample for you to try out: