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POBetter way to load image synchronously on Windows Phone?
 

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  1. POBetter way to load image synchronously on Windows Phone?
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    <p>I'm new to do C# Windows Phone programming.</p> <p>In a nutshell, I am currently building an app that will:</p> <p>Load <code>image A</code></p> <p>Load <code>image B</code></p> <p>and then Load <code>image C</code></p> <p>then use these 3 images to do some post processing.</p> <p>My Image B and Image C are build as <code>Content</code> within the project. Image A is chosen from Gallery or taken via camera, or we can simply assume that Image A is load from Isolated Storage.</p> <p>I am experiencing a problem which I believe caused by asynchronous image loading.</p> <p>Here's my code:</p> <pre><code>... // I intend to load the 3 pictures by calling the method: LoadImage(int id) and LoadCImage(); else if (ListBox.SelectedIndex == 0) { Debug.WriteLine("Selected 0"); PhotoProcessor pp = new PhotoProcessor(); WriteableBitmap imageA = new WriteableBitmap(AImage); WriteableBitmap imageB = LoadImage(0); WriteableBitmap imageC = LoadCImage(); WriteableBitmap mix = pp.Mix(pp.CalcAverageColour(0), imageA, imageB, imageC); resultPic.Source = mix; } ... </code></pre> <p>And:</p> <pre><code>private WriteableBitmap LoadImage(int id) { //String uriString = "/Assets/img0.jpg"; //BitmapImage img = new BitmapImage(new Uri(uriString, UriKind.Relative)); BitmapImage img = new BitmapImage(); img.CreateOptions = BitmapCreateOptions.None; //img.SetSource(Application.GetResourceStream(new Uri("/Assets/facetemplate0.jpg", UriKind.Relative)).Stream); img.UriSource = new Uri("/Assets/img" + id + ".jpg", UriKind.Relative); //img.UriSource = new Uri(uriString, UriKind.Relative); return new WriteableBitmap(img); } private WriteableBitmap LoadCImage() { //BitmapImage img = new BitmapImage(new Uri("/Assets/imgC.jpg", UriKind.Relative)); BitmapImage bmp = new BitmapImage(); bmp.CreateOptions = BitmapCreateOptions.None; //img.SetSource(Application.GetResourceStream(new Uri("/Assets/imgC.jpg", UriKind.Relative)).Stream); bmp.UriSource = new Uri("/Assets/imgC.jpg", UriKind.Relative); return new WriteableBitmap(bmp); } </code></pre> <p>Now my question is:</p> <p>When I'm trying to run this code, it will throw a Null Reference Exception, which is because of the function <code>mix</code> can't load Image A B and C (loading this images are asynchronously).</p> <p>I wonder if there's a way to let me sequentially load these images then let me to pass them to the <code>mix</code> function?</p> <p>What I've tried:</p> <ol> <li><p>By checking <a href="http://blogs.msdn.com/b/swick/archive/2011/04/07/image-tips-for-windows-phone-7.aspx" rel="nofollow">this great blog post</a>, I'm able to know that there do have some way to load the image synchronously, but as you can see throughout my code, I tried to use <code>SetSource(stream)</code> like the blogpost, but unfortunately I got the same Null Reference Exception.</p></li> <li><p>I've also thought about the <code>EventHandler</code> method, however I don't think its a good idea in this case. If I implement <code>EventHandler</code>, would it be something like(pseudo code):</p> <pre><code>imageA_Opened() { LoadImageB += imageB_Opened(); } imageB_Opened() { LoadImageC += imageC_Opened(); } imageC_Opened() { PhotoProcessor pp = new PhotoProcessor(); pp.Mix(averageColour, A, B, C); } </code></pre></li> </ol> <p>Am I right?</p>
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