127 lines
2.3 KiB
C++
127 lines
2.3 KiB
C++
#pragma once
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#include <cgv/math/vec.h>
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#include <cgv/math/mat.h>
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#include <cgv/math/functions.h>
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#include <limits>
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namespace cgv{
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namespace math{
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/**
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* Implementation of 1d and 2d linear time distance transformation
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* see: "Distance Transforms of Sampled Functions
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* Pedro F. Felzenszwalb and Daniel P. Huttenlocher"
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* for details.
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*
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*/
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template <typename T>
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void sqrdist_transf_1d(const vec<T>& f, vec<T>& d)
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{
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static T INF =std::numeric_limits<T>::max();
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unsigned n = f.size();
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d.resize(n);
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int *v = new int[n];
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T *z = new T[n+1];
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int k = 0;
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v[0] = 0;
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z[0] = -INF;
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z[1] = +INF;
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for (unsigned q = 1; q <= n-1; q++)
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{
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T s = ((f[q]+sqr(q))-(f[v[k]]+sqr(v[k])))/(2*q-2*v[k]);
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while (s <= z[k])
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{
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k--;
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s = ((f[q]+sqr(q))-(f[v[k]]+sqr(v[k])))/(2*q-2*v[k]);
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}
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k++;
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v[k] = q;
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z[k] = s;
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z[k+1] = +INF;
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}
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k = 0;
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for (unsigned q = 0; q <= n-1; q++)
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{
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while (z[k+1] < q)
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k++;
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d[q] = sqr(q-v[k]) + f[v[k]];
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}
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delete [] v;
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delete [] z;
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}
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template <typename T>
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void sqrdist_transf_2d(mat<T> &im)
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{
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static T INF =std::numeric_limits<T>::max();
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unsigned width = im.ncols();
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unsigned height = im.nrows();
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vec<T> d;
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// transform along columns
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for (unsigned x = 0; x < width; x++)
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{
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sqrdist_transf_1d<T>(im.col(x), d);
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im.set_col(x, d);
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}
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// transform along rows
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for (unsigned y = 0; y < height; y++)
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{
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sqrdist_transf_1d<T>(im.row(y), d);
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im.set_row(y, d);
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}
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}
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///compute the squared distance transform of an input image
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template <typename T>
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void sqrdist_transf_2d(const mat<T>& input,mat<T>& output,T on = 1)
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{
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static T INF =std::numeric_limits<T>::max();
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unsigned width = input.nrows();
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unsigned height = input.ncols();
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output.resize(width,height);
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for (unsigned y = 0; y < height; y++)
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{
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for (unsigned x = 0; x < width; x++)
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{
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if (input(x,y) == on)
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output(x,y) = 0;
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else
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output(x,y) = INF;
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}
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}
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sqrdist_transf_2d<T>(output);
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}
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///compute the distance transform of an input image
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template <typename T>
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void dist_transf_2d(mat<T>& input, mat<T>& output,T on = 1)
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{
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sqrdist_transf_2d(input,output,on );
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for(unsigned y = 0; y < output.ncols();y++)
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{
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for(unsigned x = 0; x < output.nrows();x++)
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{
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output(x,y)=sqrt(output(x,y));
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}
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}
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}
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}
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}
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