How to use

normalizeL2

method

in

boofcv.alg.descriptor.UtilFeature

/**
 * Adjusts the descriptor.  This adds lighting invariance and reduces the affects of none-affine changes
 * in lighting.
 *
 * 1) Apply L2 normalization
 * 2) Clip using max descriptor value
 * 3) Apply L2 normalization again
 */
public static void normalizeDescriptor(TupleDesc_F64 descriptor , double maxDescriptorElementValue ) {
  // normalize descriptor to unit length
  UtilFeature.normalizeL2(descriptor);
  // clip the values
  for (int i = 0; i < descriptor.size(); i++) {
    double value = descriptor.value[i];
    if( value > maxDescriptorElementValue ) {
      descriptor.value[i] = maxDescriptorElementValue;
    }
  }
  // normalize again
  UtilFeature.normalizeL2(descriptor);
}

/**
 * <p>
 * Computes the SURF descriptor for the specified interest point.  If the feature
 * goes outside of the image border (including convolution kernels) then null is returned.
 * </p>
 *
 * @param x Location of interest point.
 * @param y Location of interest point.
 * @param angle The angle the feature is pointing at in radians.
 * @param scale Scale of the interest point. Null is returned if the feature goes outside the image border.
 * @param ret storage for the feature. Must have 64 values.
 */
public void describe(double x, double y, double angle, double scale, BrightFeature ret)
{
  describe(x, y, angle, scale, (TupleDesc_F64) ret);
  // normalize feature vector to have an Euclidean length of 1
  // adds light invariance
  UtilFeature.normalizeL2(ret);
  // Laplacian's sign
  ret.white = computeLaplaceSign((int)(x+0.5),(int)(y+0.5), scale);
}

public void describe(double x, double y, double angle, double scale, BrightFeature desc)
{
  int featureIndex = 0;
  for( int band = 0; band < ii.getNumBands(); band++ ) {
    describe.setImage(ii.getBand(band));
    describe.describe(x,y, angle, scale, bandDesc);
    System.arraycopy(bandDesc.value,0,desc.value,featureIndex,bandDesc.size());
    featureIndex += bandDesc.size();
  }
  UtilFeature.normalizeL2(desc);
  describe.setImage(grayII);
  desc.white = describe.computeLaplaceSign((int)(x+0.5),(int)(y+0.5),scale);
}