In opencv 2.4.9, I use the feature matching method SIFT.
that field might be unused (ignored) for SIFT, but used by other descriptor algorithms.
size looks like the next best thing, and its value looks sensible.
I took a peek in the source. seems to mean something afterall!
>>> hex(11_469_311)
'0xaf01ff'
and it’s building that from three byte sized values, 0xFF (octave), 0x01 (layer?), 0xAF (xi??)
img.at<sift_wt>(r-1, c+1) + img.at<sift_wt>(r-1, c-1)) * cross_deriv_scale; float tr = dxx + dyy; float det = dxx * dyy - dxy * dxy; if( det <= 0 || tr*tr*edgeThreshold >= (edgeThreshold + 1)*(edgeThreshold + 1)*det ) return false; } kpt.pt.x = (c + xc) * (1 << octv); kpt.pt.y = (r + xr) * (1 << octv); kpt.octave = octv + (layer << 8) + (cvRound((xi + 0.5)*255) << 16); kpt.size = sigma*powf(2.f, (layer + xi) / nOctaveLayers)*(1 << octv)*2; kpt.response = std::abs(contr); return true; } namespace { class findScaleSpaceExtremaT {
} String SIFT::getDefaultName() const { return (Feature2D::getDefaultName() + ".SIFT"); } static inline void unpackOctave(const KeyPoint& kpt, int& octave, int& layer, float& scale) { octave = kpt.octave & 255; layer = (kpt.octave >> 8) & 255; octave = octave < 128 ? octave : (-128 | octave); scale = octave >= 0 ? 1.f/(1 << octave) : (float)(1 << -octave); } static Mat createInitialImage( const Mat& img, bool doubleImageSize, float sigma ) { CV_TRACE_FUNCTION(); Mat gray, gray_fpt;
Thanks for your reply.
crackwitz:
unpackOctave
, it seems to work.
