WPF frozen BitmapImage not showing

Question

I am using a viewmodel bound to an image property on the UI and the viewmodel contains an ImageSource property. I set that property using the following function

    private BitmapImage GetImageFromUri(Uri urisource)
    {
        if (urisource == null)
            return null;

        var image = new BitmapImage();
        image.BeginInit();
        image.UriSource = urisource;
        image.EndInit();
        image.Freeze(); //commenting this shows the image if the routine is called from the proper thread.

        return image;
   }

For some odd reason, in the following code, when I call Freeze on my BitmapImage, it does not appear on the main window.I get no exception or crash. Can anybody help me with this? I am setting the image property asynchronously so I need to be able to use the created image, assuming the GetImageFromUri call was made from a thread other than the UI thread.

score 3 · Answer 1 · answered Oct 25 '11 at 16:31

3

Try setting the CacheOption for BitmapImage before freezing it. See if this works -

var image = new BitmapImage();
image.BeginInit();
image.CacheOption = BitmapCacheOption.OnLoad;
image.UriSource = urisource;
image.EndInit();
image.Freeze();

answered Oct 25 '11 at 16:31

Rohit Vats

79,502
12
161
185

score 1 · Answer 2 · answered Oct 25 '11 at 16:03

1

Before you freeze it, you need to fully render it.
You should try to listen to the SourceUpdated event, and only then freeze the image.

On a side note, if you ever want to modify the Image after that, you will have to Clone it.

answered Oct 25 '11 at 16:03

Louis Kottmann

16,268
4
64
88

What do you mean by render it? – ak3nat0n Oct 25 '11 at 16:20
Graphically rendered. Settings the source does not make it visualizable, WPF first needs to render the image. It looks like you're freezing it before WPF gets the chance to do it. – Louis Kottmann Oct 25 '11 at 16:28

Smagin Alexey · Answer 3 · 2019-02-07T10:56:54.777

IF i use StreamSource, for me is enough:

public static BitmapSource ToBitmap(this MemoryStream stream)
    {
        try
        {
            using (stream)
            {
                stream.Position = 0;
                var image = new BitmapImage();
                image.BeginInit();
                image.CacheOption = BitmapCacheOption.OnLoad;
                image.StreamSource = stream;
                image.EndInit();
                image.Freeze();
                return image;
            }
        }
        catch (Exception)
        {
            return null;
        }
    }

But if i use UriSource i need:

public static async Task<BitmapSource> ToBitmapAsync(this string sourceUri)
    {
        try
        {
            using (var client = new WebClient())
            using (var stream = await client.OpenReadTaskAsync(new Uri(sourceUri)))
            using (var ms = new MemoryStream())
            {
                stream.CopyTo(ms);
                return ms.ToBitmap();
            }
        }
        catch (Exception)
        {
            return null;
        }
    }

BitmapSource has UriSource, but it works after xaml rendered

WPF frozen BitmapImage not showing

3 Answers3