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Tensor.cpp
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Tensor.cpp
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#include "header.h"
FImage *computeStructureTensors(FImage *img)
{
int w = img->width;
int h = img->height;
FImage *tensors = new FImage(w, h);
for (int y = 0; y < h; y++)
{
for (int x = 0; x < w; x++)
{
float uv[3];
uv[0] = x;
uv[1] = y;
uv[2] = 0.;
float d[3];
d[0] = 1;
d[1] = 1;
d[2] = 0.;
float dx[3];
float dy[3];
float a3[3];
float b3[3];
float c3[3];
float d3[3];
float e3[3];
float f3[3];
img->get(uv[0] - d[0], uv[1] - d[1], a3);
img->get(uv[0] - d[0], uv[1] , b3);
img->get(uv[0] - d[0], uv[1] + d[1], c3);
img->get(uv[0] + d[0], uv[1] - d[1], d3);
img->get(uv[0] + d[0], uv[1] , e3);
img->get(uv[0] + d[0], uv[1] + d[1], f3);
dx[0] = (
-1.0 * a3[0] +
-2.0 * b3[0] +
-1.0 * c3[0] +
+1.0 * d3[0] +
+2.0 * e3[0] +
+1.0 * f3[0]
) / 4.0;
dx[1] = (
-1.0 * a3[1] +
-2.0 * b3[1] +
-1.0 * c3[1] +
+1.0 * d3[1] +
+2.0 * e3[1] +
+1.0 * f3[1]
) / 4.0;
dx[2] = (
-1.0 * a3[2] +
-2.0 * b3[2] +
-1.0 * c3[2] +
+1.0 * d3[2] +
+2.0 * e3[2] +
+1.0 * f3[2]
) / 4.0;
img->get(uv[0] - d[0], uv[1] - d[1], a3);
img->get(uv[0] , uv[1] - d[1], b3);
img->get(uv[0] + d[0], uv[1] - d[1], c3);
img->get(uv[0] - d[0], uv[1] + d[1], d3);
img->get(uv[0] , uv[1] + d[1], e3);
img->get(uv[0] + d[0], uv[1] + d[1], f3);
dy[0] = (
-1.0 * a3[0] +
-2.0 * b3[0] +
-1.0 * c3[0] +
+1.0 * d3[0] +
+2.0 * e3[0] +
+1.0 * f3[0]
) / 4.0;
dy[1] = (
-1.0 * a3[1] +
-2.0 * b3[1] +
-1.0 * c3[1] +
+1.0 * d3[1] +
+2.0 * e3[1] +
+1.0 * f3[1]
) / 4.0;
dy[2] = (
-1.0 * a3[2] +
-2.0 * b3[2] +
-1.0 * c3[2] +
+1.0 * d3[2] +
+2.0 * e3[2] +
+1.0 * f3[2]
) / 4.0;
float E;
E = dx[0]*dx[0]+
dx[1]*dx[1]+
dx[2]*dx[2];
float F;
F = dx[0]*dy[0]+
dx[1]*dy[1]+
dx[2]*dy[2];
float G;
G = dy[0]*dy[0]+
dy[1]*dy[1]+
dy[2]*dy[2];
tensors->set(x, y, E, F, G);
}
}
return tensors;
}
// major eigenvalue
float getLambda1(FImage *tensors, int x, int y)
{
float g[3];
tensors->get(x, y, g);
float E = g[0];
float F = g[1];
float G = g[2];
float det = sqrtf(powf(E - G, 2.f) + 4.f * F*F);
return (E + G + det) * 0.5f;
}
// minor eigenvalue
float getLambda2(FImage *tensors, int x, int y)
{
float g[3];
tensors->get(x, y, g);
float E = g[0];
float F = g[1];
float G = g[2];
float det = sqrtf(powf(E - G, 2.f) + 4.f * F*F);
return (E + G - det) * 0.5f;
}
// major eigenvector
void getV1(FImage *tensors, int x, int y, float v[3])
{
float g[3];
tensors->get(x, y, g);
float E = g[0];
float F = g[1];
float G = g[2];
float det = sqrtf(powf(E - G, 2.f) + 4.f * F*F);
v[0] = 2.f*F;
v[1] = G - E + det;
v[2] = 0.f;
}
// minor eigenvector
void getV2(FImage *tensors, int x, int y, float v[3])
{
float g[3];
tensors->get(x, y, g);
float E = g[0];
float F = g[1];
float G = g[2];
float det = sqrtf(powf(E - G, 2.f) + 4.f * F*F);
v[0] = 2.f*F;
v[1] = G - E - det;
v[2] = 0.f;
}
FImage *computeTangentFlowMap(FImage *tensors)
{
int w = tensors->width;
int h = tensors->height;
FImage *tfm = new FImage(w, h);
for (int y = 0; y < h; y++)
{
for (int x = 0; x < w; x++)
{
float lambda = getLambda2(tensors, x, y);
float v[3];
getV2(tensors, x, y, v);
float m = sqrtf(v[0]*v[0]+v[1]*v[1]);
if (m > 0.f)
{
v[0] /= m;
v[1] /= m;
tfm->set(x, y, v[0], v[1], sqrtf(lambda));
} else
{
tfm->set(x, y, 0, 1, 0);
}
}
}
return tfm;
}