Image

The Image control is a control for displaying raster images.

Binding

Binding onto an Image control's Source property with a string must be done using a binding converter that will convert the string to an IBitmap.

Examples

Swappable Image Button

An image button that changes images based on state is an example where binding to the Image control's Source property might seem necessary.

To have a button that swaps the image it's showing based on its state, you could either use a binding converter that converts a string into a IBitmap, or you could use the declarative approaches below, which don't use binding.

The declarative approaches keep images in memory and won't have to load them in on-demand, which will net you greater performance than a binding approach. You must declare every image you will use inside your XAML with the declarative approach.

Binding Converter Approach

<UserControl.Resources>
    <ext:BitmapAssetValueConverter x:Key="variableImage"/>
</UserControl.Resources>

<Image Width="75"
       Height="73"
       Source="{Binding PlaySource, Converter={StaticResource variableImage}}">

/// <summary>
/// <para>
/// Converts a string path to a bitmap asset.
/// </para>
/// <para>
/// The asset must be in the same assembly as the program. If it isn't,
/// specify "avares://<assemblynamehere>/" in front of the path to the asset.
/// </para>
/// </summary>
public class BitmapAssetValueConverter : IValueConverter
{
    public static BitmapAssetValueConverter Instance = new BitmapAssetValueConverter();

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null)
            return null;

        if (value is string rawUri && targetType.IsAssignableFrom(typeof(Bitmap)))
        {
            Uri uri;

            // Allow for assembly overrides
            if (rawUri.StartsWith("avares://"))
            {
                uri = new Uri(rawUri);
            }
            else
            {
                string assemblyName = Assembly.GetEntryAssembly().GetName().Name;
                uri = new Uri($"avares://{assemblyName}/{rawUri}");
            }

            var assets = AvaloniaLocator.Current.GetService<IAssetLoader>();
            var asset = assets.Open(uri);

            return new Bitmap(asset);
        }

        throw new NotSupportedException();
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

Declarative Approaches

Using a Button

View the "Play Button" example in the Button documentation.

Using a ToggleButton

View the "Speaker Mute Button" example in the ToggleButton documentation.

Reference

Image

Source code

Image.cs