Question

I am using a RSS feed to display content in my app. Everything works great except gif images. I have read that Silverlight doesn’t support the gif file format so I’ve been trying to use the ImageTools plugin.

There seems to be loads of examples where people click a button and the image displays on the same page but I want to call the image when my listbox is being populated.

Currently this is what I have:

XAML:

xmlns:imagetools="clr-namespace:ImageTools.Controls;assembly=ImageTools.Controls"
....
<ListBox x:Name="Weather">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel>

                            <imagetools:AnimatedImage Source="{Binding WeatherIcon, Converter={StaticResource DisplayGIF}}" />

                            <TextBlock Name="temperatureBlock" Text="{Binding WeatherTemperatureSummary}" TextWrapping="Wrap" Margin="12,0,0,0" FontSize="{Binding HeadlineSize}" Foreground="{Binding WeatherTemperatureSummary, Converter={StaticResource StylesAndColours}}" />
                            <TextBlock Name="summaryBlock" Text="{Binding Summary, Converter={StaticResource RssTextTrimmer}}" TextWrapping="Wrap" Margin="12,-6,0,10" FontSize="{Binding SummarySize}" />
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>

DisplayGif class:

using ImageTools;
using ImageTools.IO;
using ImageTools.IO.Gif;
using System.Windows.Data;
using System.Text;
using System.IO;
using System.Windows.Media.Imaging;
public class DisplayGIF : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        byte[] buffer = Encoding.Unicode.GetBytes(value.ToString());
        Stream stream = new MemoryStream(buffer);
        ExtendedImage image = new ExtendedImage();
        ImageTools.IO.Decoders.AddDecoder<GifDecoder>();
        return image.ToBitmap(); // give error that image is not loaded
    }

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

The above code fails as the image is not yet loaded. Is there a work around to this or even a better/easier way to get the gif images to display?

EDIT 1

Based on Ku6opr’s answer I have altered my class. When I start my app now it hangs as I suspect I am not managing the threads correctly.

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        byte[] buffer = Encoding.Unicode.GetBytes(value.ToString());
        Stream stream = new MemoryStream(buffer);
        ExtendedImage image = new ExtendedImage();
        ImageTools.IO.Decoders.AddDecoder<GifDecoder>();
        image.SetSource(stream);
        EventWaitHandle Wait = new AutoResetEvent(false);
        image.LoadingCompleted += (s, e) =>
        {
            Wait.Set();
        };
        Wait.WaitOne();
        return image.ToBitmap();
    }

Edit 2:

Ok, turns out the gif images I was trying to link to were not hot linkable! The link provided by Ku6opr do work – just make sure that you can actually link to the images from an outside source 😉

http://www.java2s.com/Open-Source/ASP.NET/Silverlight/imagetools/ImageTools/Controls/ImageConverter.cs.htm

Thanks,

Rich

Answer 1

Probably, it loads image asynchronously. I guess, you need to wait while it completely loaded. ExtendedImage maybe has some event (LoadingCompleted or something else)

public object Convert(object value, Type targetType, object parameter,         System.Globalization.CultureInfo culture)
{
    byte[] buffer = Encoding.Unicode.GetBytes(value.ToString());
    Stream stream = new MemoryStream(buffer);
    ImageTools.IO.Decoders.AddDecoder<GifDecoder>();
    ExtendedImage image = new ExtendedImage();
    image.Source = stream;
    EventWaithandle Wait = new AutoResetEvent(false);
    ExtendedImage.LoadingCompleted += (s, e) =>
    {
        Wait.Set();
    };        
    Wait.Wait();
    return image.ToBitmap(); // give error that image is not loaded
}

While I wrote this code I see that you never assign Stream to your image. Check it

EDIT:
ImageTools already has ImageConverter class that works with Streams, Absolute and Revative uri paths. It source code to look inside you can find here: http://www.java2s.com/Open-Source/ASP.NET/Silverlight/imagetools/ImageTools/Controls/ImageConverter.cs.htm