/// <summary>
/// Create a SURF detector using the specific values
/// </summary>
/// <param name="hessianThresh">
/// Only features with keypoint.hessian larger than that are extracted.
/// good default value is ~300-500 (can depend on the average local contrast and sharpness of the image).
/// user can further filter out some features based on their hessian values and other characteristics
/// </param>
/// <param name="extended">
/// false means basic descriptors (64 elements each),
/// true means extended descriptors (128 elements each)
/// </param>
/// <param name="nOctaves">
/// The number of octaves to be used for extraction.
/// With each next octave the feature size is doubled
/// </param>
/// <param name="nOctaveLayers">
/// The number of layers within each octave
/// </param>
/// <param name="upright">
/// False means that detector computes orientation of each feature.
/// True means that the orientation is not computed (which is much, much faster).
/// For example, if you match images from a stereo pair, or do image stitching, the matched features likely have very similar angles, and you can speed up feature extraction by setting upright=true.</param>
public SURFDetector(double hessianThresh, int nOctaves = 4, int nOctaveLayers = 2, bool extended = true, bool upright = false)
{
_ptr = ContribInvoke.CvSURFDetectorCreate(hessianThresh, nOctaves, nOctaveLayers, extended, upright, ref _feature2D);
}