As far as I know you can't specify bicubic or bilinear interpolation for a bitmap in WPF, (the default is linear) but you can set RenderOptions.BitmapScalingMode
option to get better control of the display quality of the scaled bitmap. For example:
RenderOptions.BitmapScalingMode="NearestNeighbor"
or RenderOptions.BitmapScalingMode="HighQuality"
There's more info on each of the scaling modes on MSDN http://msdn.microsoft.com/en-us/library/system.windows.media.bitmapscalingmode
If you still have issues with blurry graphics try setting UseLayoutRounding="True"
in your root element. This will disable sub-pixel positioning of elements that can can cause jagged lines in WPF applications