As far as I know, what you want to do is not possible without decoding the bitmap twice.
I guess it would be a lot simpler to just decode the bitmap to its native size and then set the size of the containing Image control as needed. The bitmap is scaled appropriately, as Stretch
is set to Uniform
(since both width and height of the Image control are set, Stretch
could as well be set to Fill
or UniformToFill
).
var bitmap = new BitmapImage(new Uri(...));
if (bitmap.Width > bitmap.Height)
{
image.Width = 475;
image.Height = image.Width * bitmap.Height / bitmap.Width;
}
else
{
image.Height = 475;
image.Width = image.Height * bitmap.Width / bitmap.Height;
}
image.Stretch = Stretch.Uniform;
image.Source = bitmap;