WINUI Scale without fuzzy

Question

I have a WinUI app:

<Image x:Name="PixelSurface" Stretch="None" HorizontalAlignment="Left" VerticalAlignment="Top">
    <Image.RenderTransform>
        <ScaleTransform ScaleX="4" ScaleY="4" />
    </Image.RenderTransform>
</Image>

It works, but the pixels get all fuzzy. Probably because it's doing some smoothing. Can I scale it up without any filters being added.

Thanks.

"Use the RenderAtScale property to render the BitmapCache at a multiple of the normal bitmap size." learn.microsoft.com/en-us/dotnet/api/… — Gerry Schmitz
– Gerry Schmitz, Commented Aug 7 at 5:16
If you want blocks for each pixel instead of a smooth image you can usually specify "nearest neighbor interpolation" when rendering. But this tend to look terrible at non integer scaling factors, and I have no idea how to specify interpolation mode in WinUI. — JonasH
– JonasH, Commented Aug 7 at 9:53

Akilan · Accepted Answer · 2025-08-10 12:59:03Z

The approach used for scaling image will not work with WinUI. It is for WPF.
Below snippet will scale the image without getting fuzzy, You need to invoke the method in your required events.

private async Task LoadAndScaleImageAsync(StorageFile file, double scaleFactor)
{
   using (IRandomAccessStream fileStream = await file.OpenAsync(FileAccessMode.Read))
   {
       BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);
       using (InMemoryRandomAccessStream scaledStream = new InMemoryRandomAccessStream())
       {
           BitmapEncoder encoder = await BitmapEncoder.CreateForTranscodingAsync(scaledStream, decoder);
           BitmapTransform transform = new BitmapTransform();
           transform.InterpolationMode = BitmapInterpolationMode.NearestNeighbor;
           transform.ScaledWidth = (uint)(decoder.PixelWidth * scaleFactor);
           transform.ScaledHeight = (uint)(decoder.PixelHeight * scaleFactor);
           encoder.BitmapTransform = transform;
           await encoder.FlushAsync();
           BitmapImage bitmapImage = new BitmapImage();
           scaledStream.Seek(0);
           await bitmapImage.SetSourceAsync(scaledStream);
           PixelSurface.Source = bitmapImage;
       }
   }
}

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