/** Detects key points inside the image and computes descriptions at those points. <br> */
protected double[][] extractFeaturesInternal(BufferedImage image) {
double[][] descriptions = harder(image);
if (!perBandNormalization) {
// if perBandNormalization is off then do a final L2 normalization
for (int i = 0; i < descriptions.length; i++) {
Normalization.normalizeL2(descriptions[i]);
// SurfDescribeOps.normalizeFeatures(descriptions[i]);
}
}
return descriptions;
}
public <II extends ImageSingleBand> double[][] harder(BufferedImage image) {
MultiSpectral<ImageFloat32> colorImage =
ConvertBufferedImage.convertFromMulti(image, null, true, ImageFloat32.class);
// convert the color image to greyscale
ImageFloat32 greyscaleImage =
ConvertImage.average((MultiSpectral<ImageFloat32>) colorImage, null);
// SURF works off of integral images
Class<II> integralType = GIntegralImageOps.getIntegralType(ImageFloat32.class);
// define the feature detection algorithm
NonMaxSuppression extractor =
FactoryFeatureExtractor.nonmax(new ConfigExtract(2, detectThreshold, 5, true));
FastHessianFeatureDetector<II> detector =
new FastHessianFeatureDetector<II>(extractor, maxFeaturesPerScale, 2, 9, 4, 4);
// estimate orientation
OrientationIntegral<II> orientation = FactoryOrientationAlgs.sliding_ii(null, integralType);
DescribePointSurf<II> descriptor =
FactoryDescribePointAlgs.<II>surfStability(null, integralType);
// compute the integral image of the greyscale 'image'
II integralgrey =
GeneralizedImageOps.createSingleBand(
integralType, greyscaleImage.width, greyscaleImage.height);
GIntegralImageOps.transform(greyscaleImage, integralgrey);
// detect fast hessian features
detector.detect(integralgrey);
// === This is the point were the code starts deviating from the standard SURF! ===
// tell algorithms which image to process
orientation.setImage(integralgrey);
List<ScalePoint> points = detector.getFoundPoints();
double[][] descriptions = new double[points.size()][3 * descriptor.getDescriptionLength()];
double[] angles = new double[points.size()];
int l = 0;
for (ScalePoint p : points) {
orientation.setScale(p.scale);
angles[l] = orientation.compute(p.x, p.y);
l++;
}
for (int i = 0; i < 3; i++) {
// check if it is actually a greyscale image, take always the 1st band!
ImageFloat32 colorImageBand = null;
if (colorImage.getNumBands() == 1) {
colorImageBand = colorImage.getBand(0);
} else {
colorImageBand = colorImage.getBand(i);
}
// compute the integral image of the i-th band of the color 'image'
II integralband =
GeneralizedImageOps.createSingleBand(
integralType, colorImageBand.width, colorImageBand.height);
GIntegralImageOps.transform(colorImageBand, integralband);
// tell algorithms which image to process
// orientation.setImage(integralband);
descriptor.setImage(integralband);
int j = 0;
for (ScalePoint p : points) {
// estimate orientation
// orientation.setScale(p.scale);
// double angle = orientation.compute(p.x, p.y);
// extract the SURF description for this region
SurfFeature desc = descriptor.createDescription();
descriptor.describe(p.x, p.y, angles[j], p.scale, (TupleDesc_F64) desc);
double[] banddesc = desc.getValue();
if (perBandNormalization) {
banddesc = Normalization.normalizeL2(banddesc);
}
for (int k = 0; k < SURFLength; k++) {
descriptions[j][i * SURFLength + k] = banddesc[k];
}
j++;
}
}
return descriptions;
}