Using the right encoder like PngBitMapEncoder should work:
private ImageSource GetImage(byte[] imageData, System.Windows.Media.PixelFormat format, int width = 640, int height = 480)
{
using (MemoryStream memoryStream = new MemoryStream())
{
PngBitmapEncoder encoder = new PngBitmapEncoder();
encoder.Interlace = PngInterlaceOption.On;
encoder.Frames.Add(BitmapFrame.Create(BitmapSource.Create(width, height, 96, 96, format, null, imageData, width * format.BitsPerPixel / 8)));
encoder.Save(memoryStream);
BitmapImage imageSource = new BitmapImage();
imageSource.BeginInit();
imageSource.StreamSource = memoryStream;
imageSource.EndInit();
return imageSource;
}
}