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[libstick.git] / 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