if (preprocSigma > 0.0) {
GaussianConvolution gaussianPre = new GaussianConvolution(preprocSigma);
img = gaussianPre.convolve(img);
}
pyr = new OctavePyramid();
pyr.setVerbose(verbose);
pyr.buildOctaves(img, startScale, scaleSpaceLevels, octaveSigma, minimumRequiredPixelsize);
globalKeypoints = new ArrayList<KeyPoint>();