blockify.hxx

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/*     Copyright 2013-2014 by Martin Bidlingmaier and Ullrich Koethe    */
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#ifndef VIGRA_BLOCKIFY_HXX
#define VIGRA_BLOCKIFY_HXX

#include "multi_array.hxx"

namespace vigra
{

namespace blockify_detail
{

template <unsigned int CurrentDimensions>
struct blockify_impl
{
    // for CurrentDimension >= 1
    template <unsigned int N, class T, class S, class Shape>
    static void make(MultiArrayView<N, T, S>& source, 
                     MultiArrayView<N, MultiArrayView<N, T, S> >& blocks,
                     Shape current_block_begin,
                     Shape current_block_end,
                     Shape current_block_pos,
                     Shape block_shape)
    {
        typedef typename Shape::value_type size_type;
        enum{ n = CurrentDimensions - 1};

        size_type blocks_extend = blocks.shape(n);
        
        vigra_assert(blocks_extend != 0, "");
        for(current_block_pos[n] = 0, current_block_begin[n] = 0, current_block_end[n] = block_shape[n];
            current_block_pos[n] != blocks_extend - 1;
            ++current_block_pos[n],
                current_block_begin[n] += block_shape[n], 
                current_block_end[n] += block_shape[n])
        {
            blockify_impl<n>::make(source, blocks, current_block_begin, current_block_end, current_block_pos, block_shape);
        }
        current_block_end[n] = source.shape(n);
        blockify_impl<n>::make(source, blocks, current_block_begin, current_block_end, current_block_pos, block_shape);
    }
};

template <>
struct blockify_impl<0>
{
    template <unsigned int N, class T, class S, class Shape>
    static void make(MultiArrayView<N, T, S>& source, 
                     MultiArrayView<N, MultiArrayView<N, T, S> >& blocks,
                     Shape current_block_begin,
                     Shape current_block_end,
                     Shape current_block_pos,
                     Shape /*block_shape*/)
    {
        blocks[current_block_pos] = source.subarray(current_block_begin, current_block_end);
    }
};

} // namespace blockify_detail

template <unsigned int N, class T, class S>
MultiArray<N, MultiArrayView<N, T, S> >
blockify(MultiArrayView<N, T, S> source, typename MultiArrayView<N, T, S>::difference_type block_shape)
{
    using namespace blockify_detail;
    typedef typename MultiArrayView<N, T, S>::difference_type Shape;

    Shape blocks_shape;
    for(unsigned int n = 0; n != N; ++n)
    {
        blocks_shape[n] = source.shape(n) / block_shape[n];
        if(blocks_shape[n] * block_shape[n] != source.shape(n))
            ++blocks_shape[n];
    }
    MultiArray<N, MultiArrayView<N, T, S> > blocks(blocks_shape);
    if(source.size() == 0)
        return blocks;
    Shape a;
    Shape b;
    Shape c;
    blockify_impl<N>::make(source, blocks, a, b, c, block_shape);
    return blocks;
}

} // namespace vigra

#endif // VIGRA_BLOCKIFY_HXX