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find_caltabfind_caltabFindCaltabfind_caltabFindCaltabFindCaltab (Operator)


find_caltabfind_caltabFindCaltabfind_caltabFindCaltabFindCaltab — Segment the standard calibration plate region in the image.


find_caltab(Image : Caltab : CalTabDescrFile, SizeGauss, MarkThresh, MinDiamMarks : )

Herror find_caltab(const Hobject Image, Hobject* Caltab, const char* CalTabDescrFile, const Hlong SizeGauss, const Hlong MarkThresh, const Hlong MinDiamMarks)

Herror T_find_caltab(const Hobject Image, Hobject* Caltab, const Htuple CalTabDescrFile, const Htuple SizeGauss, const Htuple MarkThresh, const Htuple MinDiamMarks)

Herror find_caltab(Hobject Image, Hobject* Caltab, const HTuple& CalTabDescrFile, const HTuple& SizeGauss, const HTuple& MarkThresh, const HTuple& MinDiamMarks)

HRegion HImage::FindCaltab(const HTuple& CalTabDescrFile, const HTuple& SizeGauss, const HTuple& MarkThresh, const HTuple& MinDiamMarks) const

HRegion HImageArray::FindCaltab(const HTuple& CalTabDescrFile, const HTuple& SizeGauss, const HTuple& MarkThresh, const HTuple& MinDiamMarks) const

void FindCaltab(const HObject& Image, HObject* Caltab, const HTuple& CalTabDescrFile, const HTuple& SizeGauss, const HTuple& MarkThresh, const HTuple& MinDiamMarks)

HRegion HImage::FindCaltab(const HString& CalTabDescrFile, const HTuple& SizeGauss, const HTuple& MarkThresh, Hlong MinDiamMarks) const

HRegion HImage::FindCaltab(const HString& CalTabDescrFile, Hlong SizeGauss, Hlong MarkThresh, Hlong MinDiamMarks) const

HRegion HImage::FindCaltab(const char* CalTabDescrFile, Hlong SizeGauss, Hlong MarkThresh, Hlong MinDiamMarks) const

void HOperatorSetX.FindCaltab(
[in] IHUntypedObjectX* Image, [out] IHUntypedObjectX*Caltab, [in] VARIANT CalTabDescrFile, [in] VARIANT SizeGauss, [in] VARIANT MarkThresh, [in] VARIANT MinDiamMarks)

IHRegionX* HImageX.FindCaltab(
[in] BSTR CalTabDescrFile, [in] VARIANT SizeGauss, [in] VARIANT MarkThresh, [in] Hlong MinDiamMarks)

static void HOperatorSet.FindCaltab(HObject image, out HObject caltab, HTuple calTabDescrFile, HTuple sizeGauss, HTuple markThresh, HTuple minDiamMarks)

HRegion HImage.FindCaltab(string calTabDescrFile, HTuple sizeGauss, HTuple markThresh, int minDiamMarks)

HRegion HImage.FindCaltab(string calTabDescrFile, int sizeGauss, int markThresh, int minDiamMarks)


find_caltabfind_caltabFindCaltabfind_caltabFindCaltabFindCaltab is used to determine the region of a plane calibration plate with circular marks in the input image ImageImageImageImageImageimage. The region must correspond to a standard calibration plate described in the file CalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFilecalTabDescrFile. The successfully segmented region is returned in CaltabCaltabCaltabCaltabCaltabcaltab. The operator provides two algorithms. By setting appropriate integer values in SizeGaussSizeGaussSizeGaussSizeGaussSizeGausssizeGauss, MarkThreshMarkThreshMarkThreshMarkThreshMarkThreshmarkThresh, and MinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksminDiamMarks, respectively, you invoke the standard algorithm. If you pass a tuple of parameter names in SizeGaussSizeGaussSizeGaussSizeGaussSizeGausssizeGauss and a corresponding tuple of parameter values in MarkThreshMarkThreshMarkThreshMarkThreshMarkThreshmarkThresh, or just two empty tuples, respectively, you invoke the advanced algorithm instead. In this case the value passed in MinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksminDiamMarks is ignored.

Standard algorithm

First, the input image is smoothed (see gauss_imagegauss_imageGaussImagegauss_imageGaussImageGaussImage); the size of the used filter mask is given by SizeGaussSizeGaussSizeGaussSizeGaussSizeGausssizeGauss. Afterwards, a threshold operator (see thresholdthresholdThresholdthresholdThresholdThreshold) with a minimum gray value MarkThreshMarkThreshMarkThreshMarkThreshMarkThreshmarkThresh is applied. Among the extracted connected regions the most convex region with an almost correct number of holes (corresponding to the dark marks of the calibration plate) is selected. Holes with a diameter smaller than the expected size of the marks MinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksminDiamMarks are eliminated to reduce the impact of noise. The number of marks is read from the calibration plate description file CalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFilecalTabDescrFile. The complete explanation of this file can be found within the description of gen_caltabgen_caltabGenCaltabgen_caltabGenCaltabGenCaltab.

Advanced algorithm

First, an image pyramid based on ImageImageImageImageImageimage is built. Starting from the highest pyramid level, round regions are segmented with a dynamic threshold. Then, they are associated in groups based on their mutual proximity and it is evaluated whether they can represent marks of a potential calibration plate. The search is terminated once the expected number of marks has been identified in one group. The surrounding lighter area is returned in CaltabCaltabCaltabCaltabCaltabcaltab.

The image pyramid makes the search independent from the size of the image and the marks. The dynamic threshold makes the algorithm immune to bad or irregular illumination. Therefore, in general, no parameter is required. Yet, you can adjust some auxiliary parameters of the advanced algorithm by passing a list of parameter names (strings) to SizeGaussSizeGaussSizeGaussSizeGaussSizeGausssizeGauss and a list of corresponding parameter values to MarkThreshMarkThreshMarkThreshMarkThreshMarkThreshmarkThresh. Currently the following parameter is supported:


Tolerance factor for gaps between the marks. If the marks appear closer to each other than expected, you might set 'gap_tolerance'"gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance" < 1.0 to avoid disturbing patterns outside the calibration plate to be associated with the calibration plate. This can typically happen if the plate is strongly tilted and positioned in front of a background that exposes mark-like patterns. If the distances between single marks deviate significantly, e.g., if the calibration plate appears with strong perspective distortion in the image, you might set 'gap_tolerance'"gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance" > 1.0 to enforce the grouping for the more distant marks.

Suggested values: 0.75, 0.9, 1.0 (default), 1.1, 1.2, 1.5



ImageImageImageImageImageimage (input_object)  singlechannelimage(-array) objectHImageHImageHImageHImageXHobject (byte / uint2)

Input image.

CaltabCaltabCaltabCaltabCaltabcaltab (output_object)  region objectHRegionHRegionHRegionHRegionXHobject *

Output region.

CalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFileCalTabDescrFilecalTabDescrFile (input_control) HTupleHTupleHTupleVARIANTHtuple (string) (string) (HString) (char*) (BSTR) (char*)

File name of the calibration plate description.

Default value: 'caltab.descr' "caltab.descr" "caltab.descr" "caltab.descr" "caltab.descr" "caltab.descr"

List of values: 'caltab.descr'"caltab.descr""caltab.descr""caltab.descr""caltab.descr""caltab.descr", 'caltab_100mm.descr'"caltab_100mm.descr""caltab_100mm.descr""caltab_100mm.descr""caltab_100mm.descr""caltab_100mm.descr", 'caltab_10mm.descr'"caltab_10mm.descr""caltab_10mm.descr""caltab_10mm.descr""caltab_10mm.descr""caltab_10mm.descr", 'caltab_200mm.descr'"caltab_200mm.descr""caltab_200mm.descr""caltab_200mm.descr""caltab_200mm.descr""caltab_200mm.descr", 'caltab_30mm.descr'"caltab_30mm.descr""caltab_30mm.descr""caltab_30mm.descr""caltab_30mm.descr""caltab_30mm.descr"

File extension: .descr

SizeGaussSizeGaussSizeGaussSizeGaussSizeGausssizeGauss (input_control)  integer(-array) HTupleHTupleHTupleVARIANTHtuple (integer / string) (int / long / string) (Hlong / HString) (Hlong / char*) (Hlong / BSTR) (Hlong / char*)

Filter size of the Gaussian.

Default value: 3

List of values: 0, 3, 5, 7, 9, 11, 'gap_tolerance'"gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance""gap_tolerance"

MarkThreshMarkThreshMarkThreshMarkThreshMarkThreshmarkThresh (input_control)  integer(-array) HTupleHTupleHTupleVARIANTHtuple (integer / real) (int / long / double) (Hlong / double) (Hlong / double) (Hlong / double) (Hlong / double)

Threshold value for mark extraction.

Default value: 112

List of values: 48, 64, 80, 96, 112, 128, 144, 160, 0.5, 0.9, 1.0, 1.1, 1.5

MinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksMinDiamMarksminDiamMarks (input_control)  integer HTupleHTupleHTupleVARIANTHtuple (integer) (int / long) (Hlong) (Hlong) (Hlong) (Hlong)

Expected minimal diameter of the marks on the calibration plate.

Default value: 5

List of values: 3, 5, 9, 15, 30, 50, 70

Example (HDevelop)

* read calibration image
read_image(Image, 'calib-01')
* find calibration pattern
find_caltab(Image, Caltab, 'caltab.descr', 3, 112, 5)

Example (HDevelop)

* read calibration image
read_image(Image, 'calib-01')
* find calibration pattern
find_caltab(Image, Caltab, 'caltab.descr', 3, 112, 5)

Example (HDevelop)

* read calibration image
read_image(Image, 'calib-01')
* find calibration pattern
find_caltab(Image, Caltab, 'caltab.descr', 3, 112, 5)

Example (C++ (HALCON 5.0-10.0))

// read calibration image
HImage Image("calib-01") ;
// find calibration pattern
HRegion Caltab = Image.FindCaltab("caltab.descr", 3,112, 5);

Example (HDevelop)

* read calibration image
read_image(Image, 'calib-01')
* find calibration pattern
find_caltab(Image, Caltab, 'caltab.descr', 3, 112, 5)

Example (HDevelop)

* read calibration image
read_image(Image, 'calib-01')
* find calibration pattern
find_caltab(Image, Caltab, 'caltab.descr', 3, 112, 5)


find_caltabfind_caltabFindCaltabfind_caltabFindCaltabFindCaltab returns 2 (H_MSG_TRUE) if all parameter values are correct and an image region is found. The behavior in case of empty input (no image given) can be set via set_system(::'no_object_result',<Result>:)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>) and the behavior in case of an empty result region via set_system(::'store_empty_region',<'true'/'false'>:)set_system("store_empty_region",<"true"/"false">)SetSystem("store_empty_region",<"true"/"false">)set_system("store_empty_region",<"true"/"false">)SetSystem("store_empty_region",<"true"/"false">)SetSystem("store_empty_region",<"true"/"false">). If necessary, an exception is raised.

Possible Predecessors


Possible Successors


See also

find_marks_and_posefind_marks_and_poseFindMarksAndPosefind_marks_and_poseFindMarksAndPoseFindMarksAndPose, camera_calibrationcamera_calibrationCameraCalibrationcamera_calibrationCameraCalibrationCameraCalibration, disp_caltabdisp_caltabDispCaltabdisp_caltabDispCaltabDispCaltab, sim_caltabsim_caltabSimCaltabsim_caltabSimCaltabSimCaltab, caltab_pointscaltab_pointsCaltabPointscaltab_pointsCaltabPointsCaltabPoints, gen_caltabgen_caltabGenCaltabgen_caltabGenCaltabGenCaltab



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