distancetransform.hxx

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#ifndef VIGRA_DISTANCETRANSFORM_HXX
#define VIGRA_DISTANCETRANSFORM_HXX

#include <cmath>
#include "stdimage.hxx"
#include "multi_shape.hxx"

namespace vigra {

/*
 * functors to determine the distance norm
 * these functors assume that dx and dy are positive
 * (this is OK for use in internalDistanceTransform())
 */

// chessboard metric
struct InternalDistanceTransformLInifinityNormFunctor
{
    float operator()(float dx, float dy) const
    {
        return (dx < dy) ? dy : dx;
    }
};

// Manhattan metric
struct InternalDistanceTransformL1NormFunctor
{
    float operator()(float dx, float dy) const
    {
        return dx + dy;
    }
};

// Euclidean metric
struct InternalDistanceTransformL2NormFunctor
{
    float operator()(float dx, float dy) const
    {
        return VIGRA_CSTD::sqrt(dx*dx + dy*dy);
    }
};


template <class SrcImageIterator, class SrcAccessor,
                   class DestImageIterator, class DestAccessor,
                   class ValueType, class NormFunctor>
void
internalDistanceTransform(SrcImageIterator src_upperleft,
                SrcImageIterator src_lowerright, SrcAccessor sa,
                DestImageIterator dest_upperleft, DestAccessor da,
                ValueType background, NormFunctor norm)
{
    int w = src_lowerright.x - src_upperleft.x;
    int h = src_lowerright.y - src_upperleft.y;

    FImage xdist(w,h), ydist(w,h);

    xdist = (FImage::value_type)w;    // init x and
    ydist = (FImage::value_type)h;    // y distances with 'large' values

    SrcImageIterator sy = src_upperleft;
    DestImageIterator ry = dest_upperleft;
    FImage::Iterator xdy = xdist.upperLeft();
    FImage::Iterator ydy = ydist.upperLeft();
    SrcImageIterator sx = sy;
    DestImageIterator rx = ry;
    FImage::Iterator xdx = xdy;
    FImage::Iterator ydx = ydy;

    const Diff2D left(-1, 0);
    const Diff2D right(1, 0);
    const Diff2D top(0, -1);
    const Diff2D bottom(0, 1);

    int x,y;
    if(sa(sx) != background)    // first pixel
    {
        *xdx = 0.0;
        *ydx = 0.0;
        da.set(0.0, rx);
    }
    else
    {
        da.set(norm(*xdx, *ydx), rx);
    }


    for(x=1, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x;
        x<w;
        ++x, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x)   // first row left to right
    {
        if(sa(sx) != background)
        {
            *xdx = 0.0;
            *ydx = 0.0;
            da.set(0.0, rx);
        }
        else
        {
            *xdx  = xdx[left] + 1.0f;   // propagate x and
            *ydx  = ydx[left];         // y components of distance from left pixel
            da.set(norm(*xdx, *ydx), rx); // calculate distance from x and y components
        }
    }
    for(x=w-2, xdx.x -= 2, ydx.x -= 2, sx.x -= 2, rx.x -= 2;
        x>=0;
        --x, --xdx.x, --ydx.x, --sx.x, --rx.x)   // first row right to left
    {
        float d = norm(xdx[right] + 1.0f, ydx[right]);

        if(da(rx) < d) continue;

        *xdx = xdx[right] + 1.0f;
        *ydx = ydx[right];
        da.set(d, rx);
    }
    for(y=1, ++xdy.y, ++ydy.y, ++sy.y, ++ry.y;
        y<h;
        ++y, ++xdy.y, ++ydy.y, ++sy.y, ++ry.y)   // top to bottom
    {
        sx = sy;
        rx = ry;
        xdx = xdy;
        ydx = ydy;

        if(sa(sx) != background)    // first pixel of current row
        {
            *xdx = 0.0f;
            *ydx = 0.0f;
            da.set(0.0, rx);
        }
        else
        {
            *xdx = xdx[top];
            *ydx = ydx[top] + 1.0f;
            da.set(norm(*xdx, *ydx), rx);
        }

        for(x=1, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x;
            x<w;
            ++x, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x)  // current row left to right
        {
            if(sa(sx) != background)
            {
                *xdx = 0.0f;
                *ydx = 0.0f;
                da.set(0.0, rx);
            }
            else
            {
                float d1 = norm(xdx[left] + 1.0f, ydx[left]);
                float d2 = norm(xdx[top], ydx[top] + 1.0f);

                if(d1 < d2)
                {
                    *xdx = xdx[left] + 1.0f;
                    *ydx = ydx[left];
                    da.set(d1, rx);
                }
                else
                {
                    *xdx = xdx[top];
                    *ydx = ydx[top] + 1.0f;
                    da.set(d2, rx);
                }
            }
        }
        for(x=w-2, xdx.x -= 2, ydx.x -= 2, sx.x -= 2, rx.x -= 2;
            x>=0;
            --x, --xdx.x, --ydx.x, --sx.x, --rx.x)  // current row right to left
        {
            float d1 = norm(xdx[right] + 1.0f, ydx[right]);

            if(da(rx) < d1) continue;

            *xdx = xdx[right] + 1.0f;
            *ydx = ydx[right];
            da.set(d1, rx);
        }
    }
    for(y=h-2, xdy.y -= 2, ydy.y -= 2, sy.y -= 2, ry.y -= 2;
        y>=0;
        --y, --xdy.y, --ydy.y, --sy.y, --ry.y)    // bottom to top
    {
        sx = sy;
        rx = ry;
        xdx = xdy;
        ydx = ydy;

        float d = norm(xdx[bottom], ydx[bottom] + 1.0f);
        if(d < da(rx))    // first pixel of current row
        {
            *xdx = xdx[bottom];
            *ydx = ydx[bottom] + 1.0f;
            da.set(d, rx);
        }

        for(x=1, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x;
            x<w;
            ++x, ++xdx.x, ++ydx.x, ++sx.x, ++rx.x)  // current row left to right
        {
            float d1 = norm(xdx[left] + 1.0f, ydx[left]);
            float d2 = norm(xdx[bottom], ydx[bottom] + 1.0f);

            if(d1 < d2)
            {
                if(da(rx) < d1) continue;
                *xdx = xdx[left] + 1.0f;
                *ydx = ydx[left];
                da.set(d1, rx);
            }
            else
            {
                if(da(rx) < d2) continue;
                *xdx = xdx[bottom];
                *ydx = ydx[bottom] + 1.0f;
                da.set(d2, rx);
            }
        }
        for(x=w-2, xdx.x -= 2, ydx.x -= 2, sx.x -= 2, rx.x -= 2;
            x>=0;
            --x, --xdx.x, --ydx.x, --sx.x, --rx.x)  // current row right to left
        {
            float d1 = norm(xdx[right] + 1.0f, ydx[right]);

            if(da(rx) < d1) continue;
            *xdx = xdx[right] + 1.0f;
            *ydx = ydx[right];
            da.set(d1, rx);
        }
    }
}

/********************************************************/
/*                                                      */
/*                 distanceTransform                    */
/*                                                      */
/********************************************************/

/** \addtogroup DistanceTransform Distance Transform
*/
//@{

/** For all background pixels, calculate the distance to
    the nearest object or contour. The label of the pixels to be considered
    background in the source image is passed in the parameter 'background'.
    Source pixels with other labels will be considered objects. In the
    destination image, all pixels corresponding to background will be assigned
    the their distance value, all pixels corresponding to objects will be
    assigned 0.

    The parameter 'norm' gives the distance norm to be used:

    <ul>

    <li> norm == 0: use chessboard distance (L-infinity norm)
    <li> norm == 1: use Manhattan distance (L1 norm)
    <li> norm == 2: use Euclidean distance (L2 norm)

    </ul>

    If you use the L2 norm, the destination pixels must be real valued to give
    correct results.

    <b> Declarations:</b>

    pass 2D array views:
    \code
    namespace vigra {
        template <class T1, class S1,
                  class T2, class S2,
                  class ValueType>
        void
        distanceTransform(MultiArrayView<2, T1, S1> const & src,
                          MultiArrayView<2, T2, S2> dest,
                          ValueType background, int norm);
    }
    \endcode

    \deprecatedAPI{distanceTransform}
    pass \ref ImageIterators and \ref DataAccessors :
    \code
    namespace vigra {
        template <class SrcImageIterator, class SrcAccessor,
                  class DestImageIterator, class DestAccessor,
                  class ValueType>
        void distanceTransform(SrcImageIterator src_upperleft,
                               SrcImageIterator src_lowerright, SrcAccessor sa,
                               DestImageIterator dest_upperleft, DestAccessor da,
                               ValueType background, int norm);
    }
    \endcode
    use argument objects in conjunction with \ref ArgumentObjectFactories :
    \code
    namespace vigra {
        template <class SrcImageIterator, class SrcAccessor,
                  class DestImageIterator, class DestAccessor,
                  class ValueType>
        void distanceTransform(triple<SrcImageIterator, SrcImageIterator, SrcAccessor> src,
                               pair<DestImageIterator, DestAccessor> dest,
                               ValueType background, int norm);
    }
    \endcode
    \deprecatedEnd

    <b> Usage:</b>

    <b>\#include</b> <vigra/distancetransform.hxx><br>
    Namespace: vigra

    \code
    MultiArray<2, unsigned char> src(w,h), edges(w,h);
    MultiArray<2, float>         distance(w, h);
    ...

    // detect edges in src image (edges will be marked 1, background 0)
    differenceOfExponentialEdgeImage(src, edges, 0.8, 4.0);

    // find distance of all pixels from nearest edge
    distanceTransform(edges, distance, 0,                   2);
    //                                 ^ background label   ^ norm (Euclidean)
    \endcode

    \deprecatedUsage{distanceTransform}
    \code

    vigra::BImage src(w,h), edges(w,h);
    vigra::FImage distance(w, h);

    // empty edge image
    edges = 0;
    ...

    // detect edges in src image (edges will be marked 1, background 0)
    vigra::differenceOfExponentialEdgeImage(srcImageRange(src), destImage(edges),
                                     0.8, 4.0);

    // find distance of all pixels from nearest edge
    vigra::distanceTransform(srcImageRange(edges), destImage(distance),
                             0,                   2);
    //                       ^ background label   ^ norm (Euclidean)
    \endcode
    <b> Required Interface:</b>
    \code

    SrcImageIterator src_upperleft, src_lowerright;
    DestImageIterator dest_upperleft;

    SrcAccessor sa;
    DestAccessor da;

    ValueType background;
    float distance;

    sa(src_upperleft) != background;
    da(dest_upperleft) < distance;
    da.set(distance, dest_upperleft);

    \endcode
    \deprecatedEnd
*/
doxygen_overloaded_function(template <...> void distanceTransform)

template <class SrcImageIterator, class SrcAccessor,
                   class DestImageIterator, class DestAccessor,
                   class ValueType>
inline void
distanceTransform(SrcImageIterator src_upperleft,
                SrcImageIterator src_lowerright, SrcAccessor sa,
                DestImageIterator dest_upperleft, DestAccessor da,
                ValueType background, int norm)
{
    if(norm == 1)
    {
        internalDistanceTransform(src_upperleft, src_lowerright, sa,
                                  dest_upperleft, da, background,
                                  InternalDistanceTransformL1NormFunctor());
    }
    else if(norm == 2)
    {
        internalDistanceTransform(src_upperleft, src_lowerright, sa,
                                  dest_upperleft, da, background,
                                  InternalDistanceTransformL2NormFunctor());
    }
    else
    {
        internalDistanceTransform(src_upperleft, src_lowerright, sa,
                                  dest_upperleft, da, background,
                                  InternalDistanceTransformLInifinityNormFunctor());
    }
}

template <class SrcImageIterator, class SrcAccessor,
          class DestImageIterator, class DestAccessor,
          class ValueType>
inline void
distanceTransform(triple<SrcImageIterator, SrcImageIterator, SrcAccessor> src,
                  pair<DestImageIterator, DestAccessor> dest,
                  ValueType background, int norm)
{
    distanceTransform(src.first, src.second, src.third,
                      dest.first, dest.second, background, norm);
}

template <class T1, class S1,
          class T2, class S2,
          class ValueType>
inline void
distanceTransform(MultiArrayView<2, T1, S1> const & src,
                  MultiArrayView<2, T2, S2> dest,
                  ValueType background, int norm)
{
    vigra_precondition(src.shape() == dest.shape(),
        "distanceTransform(): shape mismatch between input and output.");
    distanceTransform(srcImageRange(src),
                      destImage(dest), background, norm);
}

//@}

} // namespace vigra

#endif // VIGRA_DISTANCETRANSFORM_HXX