Impala Documentation

template<int INDEX_SIZE, int ORI_SIZE>

void Impala::Core::Feature::FISTDescriptor< INDEX_SIZE, ORI_SIZE >::InternalSample	(	Real64 *	descriptor,
		Array::Array2dScalarReal64 *	magnitude,
		Array::Array2dScalarReal64 *	direction,
		Real64	scale,
		Real64	row,
		Real64	col,
		Real64	pointOrientation
	)			`[inline]`

Definition at line 199 of file KoenFIST2.h.

References Impala::Core::Feature::FISTDescriptor< INDEX_SIZE, ORI_SIZE >::InternalCount().

Referenced by Impala::Core::Feature::FISTDescriptor< INDEX_SIZE, ORI_SIZE >::SamplePoint().

00202     {
00203        Real64 rpos, cpos, rx, cx;
00204     
00205        // integer version of the patch center position (in image coordinates)
00206        int irow = (int) (row + 0.5);
00207        int icol = (int) (col + 0.5);
00208        Real64 sinus = sin(pointOrientation);
00209        Real64 cosinus = cos(pointOrientation);
00210               
00211        /* The spacing of index samples in terms of pixels at this scale. */
00212        const int magnificationFactor = 3;
00213        Real64 spacing = scale * magnificationFactor;
00214     
00215        /* Radius of index sample region must extend to diagonal corner of
00216           index patch plus half sample for interpolation.
00217        */
00218        Real64 radius = 1.414 * spacing * INDEX_SIZE / 2.0;
00219        int iradius = (int) (radius + 0.5);
00220        
00221        /* Examine all points from the gradient image that could lie within the
00222           index square.
00223        */
00224        for (int i = -iradius; i <= iradius; i++)
00225          for (int j = -iradius; j <= iradius; j++) {
00226              
00227            /* Rotate sample offset to make it relative to key orientation.
00228               Uses (row,col) instead of (x,y) coords.  Also, make subpixel
00229               correction as later image offset must be an integer.  Divide
00230               by spacing to put in index units.
00231            */
00232            rpos = ((cosinus * i +   sinus * j) - (row - irow)) / spacing;
00233            cpos = ((- sinus * i + cosinus * j) - (col - icol)) / spacing;
00234 
00235            // these above are relative to the center of the patch, and also
00236            // normalized to a "unit distance" (e.g. we can just put in a 
00237            // gaussian now)
00238            // simplified (compensates for deviation from integer positions):
00239            // rpos = (i - (row - irow)) / spacing;
00240            // cpos = (j - (col - icol)) / spacing;
00241              
00242            /* Compute location of sample in terms of real-valued index array
00243               coordinates.  Subtract 0.5 so that rx of 1.0 means to put full
00244               weight on index[1] (e.g., when rpos is 0 and INDEX_SIZE is 3.
00245            */
00246            rx = rpos + INDEX_SIZE / 2.0 - 0.5;
00247            cx = cpos + INDEX_SIZE / 2.0 - 0.5;
00248     
00249            /* Test whether this sample falls within boundary of index patch. */
00250            if((rx > -1.0) && (rx < (Real64) INDEX_SIZE) &&
00251               (cx > -1.0) && (cx < (Real64) INDEX_SIZE))
00252              InternalCount(descriptor, magnitude, direction, irow + i, icol + j, rpos, cpos,
00253                            rx, cx, pointOrientation);
00254          }
00255     }

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