SIFT.create constructor

SIFT.create({
  1. int nfeatures = 0,
  2. int nOctaveLayers = 3,
  3. double contrastThreshold = 0.04,
  4. double edgeThreshold = 10,
  5. double sigma = 1.6,
  6. int? descriptorType,
  7. bool enable_precise_upscale = false,
})

Create SIFT with specified descriptorType.

nfeatures The number of best features to retain. The features are ranked by their scores (measured in SIFT algorithm as the local contrast)

nOctaveLayers The number of layers in each octave. 3 is the value used in D. Lowe paper. The number of octaves is computed automatically from the image resolution.

contrastThreshold The contrast threshold used to filter out weak features in semi-uniform (low-contrast) regions. The larger the threshold, the less features are produced by the detector. Note: The contrast threshold will be divided by nOctaveLayers when the filtering is applied. When nOctaveLayers is set to default and if you want to use the value used in D. Lowe paper, 0.03, set this argument to 0.09.

edgeThreshold The threshold used to filter out edge-like features. Note that the its meaning is different from the contrastThreshold, i.e. the larger the edgeThreshold, the less features are filtered out (more features are retained).

sigma The sigma of the Gaussian applied to the input image at the octave #0. If your image is captured with a weak camera with soft lenses, you might want to reduce the number.

descriptorType The type of descriptors. Only CV_32F and CV_8U are supported.

enable_precise_upscale Whether to enable precise upscaling in the scale pyramid, which maps index $\texttt{x}$ to $\texttt{2x}$. This prevents localization bias. The option is disabled by default.

CV_WRAP static Ptr<SIFT> create(int nfeatures, int nOctaveLayers,
    double contrastThreshold, double edgeThreshold,
    double sigma, int descriptorType, bool enable_precise_upscale = false);

https://docs.opencv.org/4.x/d7/d60/classcv_1_1SIFT.html#a4264f700a8133074fb477e30d9beb331

Implementation

factory SIFT.create({
  int nfeatures = 0,
  int nOctaveLayers = 3,
  double contrastThreshold = 0.04,
  double edgeThreshold = 10,
  double sigma = 1.6,
  int? descriptorType,
  bool enable_precise_upscale = false,
}) {
  final p = calloc<cvg.SIFT>();
  cvRun(
    () => descriptorType == null
        ? cfeatures2d.cv_SIFT_create_2(
            nfeatures,
            nOctaveLayers,
            contrastThreshold,
            edgeThreshold,
            sigma,
            enable_precise_upscale,
            p,
          )
        : cfeatures2d.cv_SIFT_create_1(
            nfeatures,
            nOctaveLayers,
            contrastThreshold,
            edgeThreshold,
            sigma,
            descriptorType,
            enable_precise_upscale,
            p,
          ),
  );
  return SIFT._(p);
}