// Construct descriptor vector for this interest point
void SurfDescriptor::GetDescriptor(IPoint &ip, bool bUpright, bool bExtended)
{
int sample_x, sample_y, count = 0;
int i = 0, ix = 0, j = 0, jx = 0, xs = 0, ys = 0;
float dx, dy, mdx, mdy, co, si;
float dx_yn, mdx_yn, dy_xn, mdy_xn;
float gauss_s1 = (float)0, gauss_s2 = (float)0;
float rx = (float)0, ry = (float)0, rrx = (float)0, rry = (float)0, len = (float)0;
float cx = (float)-0.5, cy = (float)0; //Subregion centers for the 4x4 gaussian weighting
// Get rounded InterestPoint data
int X = (int)floor(ip.x + (float)0.5);
int Y = (int)floor(ip.y + (float)0.5);
int S = (int)floor(ip.scale + (float)0.5);
// Allocate descriptor memory
ip.SetDescriptorLength(64);
if (bUpright)
{
co = 1;
si = 0;
}
else
{
co = (float)cos(ip.orientation);
si = (float)sin(ip.orientation);
}
//Calculate descriptor for this interest point
i = -8;
while (i < 12)
{
j = -8;
i = i - 4;
cx += (float)1;
cy = (float)-0.5;
while (j < 12)
{
cy += (float)1;
j = j - 4;
ix = i + 5;
jx = j + 5;
dx = dy = mdx = mdy = (float)0;
dx_yn = mdx_yn = dy_xn = mdy_xn = (float)0;
xs = (int)floor(X + (-jx * S * si + ix * S * co) + (float)0.5);
ys = (int)floor(Y + (jx * S * co + ix * S * si) + (float)0.5);
// zero the responses
dx = dy = mdx = mdy = (float)0;
dx_yn = mdx_yn = dy_xn = mdy_xn = (float)0;
for (int k = i; k < i + 9; ++k)
{
for (int l = j; l < j + 9; ++l)
{
//Get coords of sample point on the rotated axis
sample_x = (int)floor(X + (-l * S * si + k * S * co) + (float)0.5);
sample_y = (int)floor(Y + (l * S * co + k * S * si) + (float)0.5);
//Get the gaussian weighted x and y responses
gauss_s1 = Gaussian(xs - sample_x, ys - sample_y, (float)2.5 * S);
rx = (float)img->HaarX(sample_y, sample_x, 2 * S);
ry = (float)img->HaarY(sample_y, sample_x, 2 * S);
//Get the gaussian weighted x and y responses on rotated axis
rrx = gauss_s1 * (-rx * si + ry * co);
rry = gauss_s1 * (rx * co + ry * si);
if (bExtended)
{
// split x responses for different signs of y
if (rry >= 0)
{
dx += rrx;
mdx += fabs(rrx);
}
else
{
dx_yn += rrx;
mdx_yn += fabs(rrx);
}
// split y responses for different signs of x
if (rrx >= 0)
{
dy += rry;
mdy += fabs(rry);
}
else
{
dy_xn += rry;
mdy_xn += fabs(rry);
}
}
else
{
dx += rrx;
dy += rry;
mdx += fabs(rrx);
mdy += fabs(rry);
}
}
}
//Add the values to the descriptor vector
gauss_s2 = Gaussian(cx - (float)2, cy - (float)2, (float)1.5);
ip.descriptor[count++] = dx * gauss_s2;
ip.descriptor[count++] = dy * gauss_s2;
ip.descriptor[count++] = mdx * gauss_s2;
ip.descriptor[count++] = mdy * gauss_s2;
// add the extended components
if (bExtended)
{
ip.descriptor[count++] = dx_yn * gauss_s2;
ip.descriptor[count++] = dy_xn * gauss_s2;
ip.descriptor[count++] = mdx_yn * gauss_s2;
ip.descriptor[count++] = mdy_xn * gauss_s2;
}
len += (dx * dx + dy * dy + mdx * mdx + mdy * mdy
+ dx_yn + dy_xn + mdx_yn + mdy_xn) * gauss_s2 * gauss_s2;
j += 9;
}
i += 9;
}
//Convert to Unit Vector
len = (float)sqrt((double)len);
if (len > 0)
{
for (int d = 0; d < ip.descriptorLength; ++d)
{
ip.descriptor[d] /= len;
}
}
}
