include/libstick-0.1/image.h

   1 #ifndef image_h_uiHiKahYooroomai
   2 #define image_h_uiHiKahYooroomai
   3
   4 #include "simplicialcomplex.h"
   5
   6
   7 namespace libstick {
   8
   9 /** We consider an image, i.e. a rectangular arrangement of pixels, of given
  10  * height and width. Every pixel has a specific value (e.g., grey value) given
  11  * by the 'values' array as concatenation of all rows. We add every pixel as
  12  * vertex with its value as simplex value. We further triangulate the resulting
  13  * rectangular latice as a grid graph together with south-west to north-east
  14  * edges for each of the small squares of the grid graph. Finally the resulting
  15  * triangles are added. For all non-vertex simplices the maximum of its
  16  * vertex-values is used as its value. The first pixel is considered to be at
  17  * bottom-left. */
  18 template<class VT, class IT>
  19 void add_image_to_complex(simplicial_complex<2, IT, VT> &s, const VT *values, size_t width, size_t height) {
  20     // Add the vertices
  21     const IT v1st = s.size();
  22     for (unsigned i=0; i < height; ++i)
  23         for (unsigned j=0; j < width; ++j)
  24             s.add_simplex(0, NULL, values[i*width + j]);
  25
  26     //      row i+1 o-------o
  27     //              |      /|
  28     //              |     / |
  29     //              |   2/  |
  30     //            0 |   /   |
  31     //              |  /    |
  32     //              | /     |
  33     //              |/  1   |
  34     //        row i o-------o
  35     //              ^
  36     //           column j
  37
  38     IT faces[3];
  39
  40     // Adding horizontal edges
  41     const IT he1st = s.size();
  42     for (unsigned i=0; i < height; ++i)
  43         for (unsigned j=0; j < width-1; ++j) {
  44             faces[0] = v1st + i*width + j;
  45             faces[1] = faces[0] + 1;
  46             s.add_simplex(1, faces);
  47         }
  48
  49     // Adding vertical edges
  50     const IT ve1st = s.size();
  51     for (unsigned i=0; i < height-1; ++i)
  52         for (unsigned j=0; j < width; ++j) {
  53             faces[0] = v1st + i*width + j;
  54             faces[1] = faces[0] + width;
  55             s.add_simplex(1, faces);
  56         }
  57
  58     // Adding diagonal edges
  59     const IT de1st = s.size();
  60     for (unsigned i=0; i < height-1; ++i)
  61         for (unsigned j=0; j < width-1; ++j) {
  62             faces[0] = v1st + i*width + j;
  63             faces[1] = faces[0] + width + 1;
  64             s.add_simplex(1, faces);
  65         }
  66
  67     // Add triangles
  68     for (unsigned i=0; i < height-1; ++i)
  69         for (unsigned j=0; j < width-1; ++j) {
  70             faces[0] = he1st + i*(width-1) + j;
  71             faces[1] = ve1st + i*width + j + 1;
  72             faces[2] = de1st + i*(width-1) + j;
  73             s.add_simplex(2, faces);
  74
  75             faces[0] = he1st + (i+1)*(width-1) + j;
  76             faces[1] = ve1st + i*width + j;
  77             faces[2] = de1st + i*(width-1) + j;
  78             s.add_simplex(2, faces);
  79         }
  80 }
  81
  82
  83 }
  84
  85 #endif
  86