critical_points_sub_pixT_critical_points_sub_pixCriticalPointsSubPixCriticalPointsSubPixcritical_points_sub_pix (Operator)

Name

critical_points_sub_pixT_critical_points_sub_pixCriticalPointsSubPixCriticalPointsSubPixcritical_points_sub_pix — Subpixel precise detection of critical points in an image.

Signature

critical_points_sub_pix(Image : : Filter, Sigma, Threshold : RowMin, ColumnMin, RowMax, ColumnMax, RowSaddle, ColumnSaddle)

Herror T_critical_points_sub_pix(const Hobject Image, const Htuple Filter, const Htuple Sigma, const Htuple Threshold, Htuple* RowMin, Htuple* ColumnMin, Htuple* RowMax, Htuple* ColumnMax, Htuple* RowSaddle, Htuple* ColumnSaddle)

void CriticalPointsSubPix(const HObject& Image, const HTuple& Filter, const HTuple& Sigma, const HTuple& Threshold, HTuple* RowMin, HTuple* ColumnMin, HTuple* RowMax, HTuple* ColumnMax, HTuple* RowSaddle, HTuple* ColumnSaddle)

void HImage::CriticalPointsSubPix(const HString& Filter, double Sigma, double Threshold, HTuple* RowMin, HTuple* ColumnMin, HTuple* RowMax, HTuple* ColumnMax, HTuple* RowSaddle, HTuple* ColumnSaddle) const

void HImage::CriticalPointsSubPix(const char* Filter, double Sigma, double Threshold, HTuple* RowMin, HTuple* ColumnMin, HTuple* RowMax, HTuple* ColumnMax, HTuple* RowSaddle, HTuple* ColumnSaddle) const

void HImage::CriticalPointsSubPix(const wchar_t* Filter, double Sigma, double Threshold, HTuple* RowMin, HTuple* ColumnMin, HTuple* RowMax, HTuple* ColumnMax, HTuple* RowSaddle, HTuple* ColumnSaddle) const   (Windows only)

static void HOperatorSet.CriticalPointsSubPix(HObject image, HTuple filter, HTuple sigma, HTuple threshold, out HTuple rowMin, out HTuple columnMin, out HTuple rowMax, out HTuple columnMax, out HTuple rowSaddle, out HTuple columnSaddle)

void HImage.CriticalPointsSubPix(string filter, double sigma, double threshold, out HTuple rowMin, out HTuple columnMin, out HTuple rowMax, out HTuple columnMax, out HTuple rowSaddle, out HTuple columnSaddle)

def critical_points_sub_pix(image: HObject, filter: str, sigma: float, threshold: float) -> Tuple[Sequence[float], Sequence[float], Sequence[float], Sequence[float], Sequence[float], Sequence[float]]

Description

critical_points_sub_pixcritical_points_sub_pixCriticalPointsSubPixCriticalPointsSubPixCriticalPointsSubPixcritical_points_sub_pix extracts critical points, i.e., local maxima, local minima, and saddle points, from the image ImageImageImageImageimageimage with subpixel precision. To do so, in each point the input image is approximated by a quadratic polynomial in x and y and subsequently the polynomial is examined for extremal values and saddle points. The partial derivatives, which are necessary for setting up the polynomial, are calculated either with various Gaussian derivatives or using the facet model, depending on FilterFilterFilterFilterfilterfilter. In the first case, SigmaSigmaSigmaSigmasigmasigma determines the size of the Gaussian kernels, while in the second case, before being processed the input image is smoothed by a Gaussian whose size is determined by SigmaSigmaSigmaSigmasigmasigma. Therefore, 'facet'"facet""facet""facet""facet""facet" results in a faster extraction at the expense of slightly less accurate results. A point is accepted to be a critical point if the absolute values of both eigenvalues of the Hessian matrix are greater than ThresholdThresholdThresholdThresholdthresholdthreshold. The eigenvalues correspond to the curvature of the gray value surface. If both eigenvalues are negative, the point is a local maximum, if both are positive, a local minimum, and if they have different signs, a saddle point.

Attention

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information

Parameters

ImageImageImageImageimageimage (input_object)  singlechannelimage objectHImageHObjectHImageHobject (byte / int1 / int2 / uint2 / int4 / real)

Input image.

FilterFilterFilterFilterfilterfilter (input_control)  string HTuplestrHTupleHtuple (string) (string) (HString) (char*)

Method for the calculation of the partial derivatives.

Default value: 'facet' "facet" "facet" "facet" "facet" "facet"

List of values: 'facet'"facet""facet""facet""facet""facet", 'gauss'"gauss""gauss""gauss""gauss""gauss"

SigmaSigmaSigmaSigmasigmasigma (input_control)  real HTuplefloatHTupleHtuple (real) (double) (double) (double)

Sigma of the Gaussian. If FilterFilterFilterFilterfilterfilter is 'facet', SigmaSigmaSigmaSigmasigmasigma may be 0.0 to avoid the smoothing of the input image.

Suggested values: 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 2.0, 3.0

Restriction: Sigma >= 0.0

ThresholdThresholdThresholdThresholdthresholdthreshold (input_control)  real HTuplefloatHTupleHtuple (real) (double) (double) (double)

Minimum absolute value of the eigenvalues of the Hessian matrix.

Default value: 5.0

Suggested values: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0

Restriction: Threshold >= 0.0

RowMinRowMinRowMinRowMinrowMinrow_min (output_control)  point.y-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Row coordinates of the detected minima.

ColumnMinColumnMinColumnMinColumnMincolumnMincolumn_min (output_control)  point.x-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Column coordinates of the detected minima.

RowMaxRowMaxRowMaxRowMaxrowMaxrow_max (output_control)  point.y-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Row coordinates of the detected maxima.

ColumnMaxColumnMaxColumnMaxColumnMaxcolumnMaxcolumn_max (output_control)  point.x-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Column coordinates of the detected maxima.

RowSaddleRowSaddleRowSaddleRowSaddlerowSaddlerow_saddle (output_control)  point.y-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Row coordinates of the detected saddle points.

ColumnSaddleColumnSaddleColumnSaddleColumnSaddlecolumnSaddlecolumn_saddle (output_control)  point.x-array HTupleSequence[float]HTupleHtuple (real) (double) (double) (double)

Column coordinates of the detected saddle points.

Result

critical_points_sub_pixcritical_points_sub_pixCriticalPointsSubPixCriticalPointsSubPixCriticalPointsSubPixcritical_points_sub_pix returns TRUE if all parameters are correct and no error occurs during the execution. If the input is empty the behavior can be set via set_system('no_object_result',<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>). If necessary, an exception is raised.

Possible Successors

gen_cross_contour_xldgen_cross_contour_xldGenCrossContourXldGenCrossContourXldGenCrossContourXldgen_cross_contour_xld, disp_crossdisp_crossDispCrossDispCrossDispCrossdisp_cross

Alternatives

local_min_sub_pixlocal_min_sub_pixLocalMinSubPixLocalMinSubPixLocalMinSubPixlocal_min_sub_pix, local_max_sub_pixlocal_max_sub_pixLocalMaxSubPixLocalMaxSubPixLocalMaxSubPixlocal_max_sub_pix, saddle_points_sub_pixsaddle_points_sub_pixSaddlePointsSubPixSaddlePointsSubPixSaddlePointsSubPixsaddle_points_sub_pix

See also

local_minlocal_minLocalMinLocalMinLocalMinlocal_min, local_maxlocal_maxLocalMaxLocalMaxLocalMaxlocal_max, plateausplateausPlateausPlateausPlateausplateaus, plateaus_centerplateaus_centerPlateausCenterPlateausCenterPlateausCenterplateaus_center, lowlandslowlandsLowlandsLowlandsLowlandslowlands, lowlands_centerlowlands_centerLowlandsCenterLowlandsCenterLowlandsCenterlowlands_center

Module

Foundation