code: protected void detectOctave( II integral , int skip , int ...featureSize ) {
  
  		int w = integral.width/skip;
  		int h = integral.height/skip;
  
  		// resize the output intensity image taking in account subsampling
  		for( int i = 0; i < intensity.length; i++ ) {
  			intensity[i].reshape(w,h);
  		}
  
  		// compute feature intensity in each level
  		for( int i = 0; i < featureSize.length; i++ ) {
  			GIntegralImageFeatureIntensity.hessian(integral,skip,featureSize[i],intensity[spaceIndex]);
  
  			spaceIndex++;
  			if( spaceIndex >= 3 )
  				spaceIndex = 0;
  
  			// find maximum in scale space
  			if( i >= 2 ) {
  				findLocalScaleSpaceMax(featureSize,i-1,skip);
  			}
  		}
  	}
docs: Computes feature intensities for all the specified feature sizes and finds features
  inside of the middle feature sizes.
  
  @param integral Integral image.
  @param skip Pixel skip factor
  @param featureSize which feature sizes should be detected.