wpf让图片自适应容器大小，而且又不会拉升变形

         <Grid Grid.Column="3"

               Margin="0,4,0,0"

               Background="Black">

             <Viewbox>

                 <Image Width="{Binding RelativeSource={RelativeSource Self}, Path=Source.PixelWidth}"

                        Height="{Binding RelativeSource={RelativeSource Self}, Path=Source.PixelHeight}"

                        Source="{Binding CtrlImage, IsAsync=True}"

                        Stretch="None" />

             </Viewbox>

         </Grid>