Function rect_iter::copy_rect_conv

pub fn copy_rect_conv<T, U, I, J>(
    source: &impl Get2D<Item = T>, 
    dest: &mut impl GetMut2D<Item = U>, 
    source_range: RectRange<I>, 
    dest_range: RectRange<J>, 
    convert: impl Fn(&T) -> U
) -> Result<(), IndexError> where
    I: Num + PartialOrd + ToPrimitive + Copy,
    J: Num + PartialOrd + ToPrimitive + Copy,