create_aniso_shape_model_xldT_create_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXld (Operator)

Name

create_aniso_shape_model_xldT_create_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXld — Prepare an anisotropically scaled shape model for matching from XLD contours.

Signature

Description

The operator create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld creates an anisotropically scaled shape model used for matching from the XLD contours passed in ContoursContoursContoursContourscontours. The XLD contours represent the gray value edges of the object to be searched for. In contrast to the operator create_aniso_shape_modelcreate_aniso_shape_modelCreateAnisoShapeModelCreateAnisoShapeModelCreateAnisoShapeModel, which creates a shape model from a template image, the operator create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld creates the shape model from XLD contours, i.e., without the use of a template image.

The output parameter ModelIDModelIDModelIDModelIDmodelID is a handle for this model, which is used in subsequent calls to find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. The center of gravity of the smallest surrounding rectangle of the ContoursContoursContoursContourscontours that is parallel to the coordinate axes is used as the origin (reference point) of the model. A different origin can be set with set_shape_model_originset_shape_model_originSetShapeModelOriginSetShapeModelOriginSetShapeModelOrigin. The model is generated for multiple image pyramid levels and is stored in memory. If a complete pregeneration of the model is selected (see below), the model is generated at multiple rotations and anisotropic scales (i.e., independent scales in the row and column direction) on each level.

Input parameters in detail

NumLevels:

The number of pyramid levels is determined with the parameter NumLevelsNumLevelsNumLevelsNumLevelsnumLevels. It should be chosen as large as possible because by this the time necessary to find the object is significantly reduced. On the other hand, NumLevelsNumLevelsNumLevelsNumLevelsnumLevels must be chosen such that the model is still recognizable and contains a sufficient number of points (at least four) on the highest pyramid level. If not enough model points are generated, the number of pyramid levels is reduced internally until enough model points are found on the highest pyramid level. If this procedure would lead to a model with no pyramid levels, i.e., if the number of model points is already too small on the lowest pyramid level, create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld returns with an error message.

If NumLevelsNumLevelsNumLevelsNumLevelsnumLevels is set to 'auto'"auto""auto""auto""auto", create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld determines the number of pyramid levels automatically. The computed number of pyramid levels can be queried using get_shape_model_paramsget_shape_model_paramsGetShapeModelParamsGetShapeModelParamsGetShapeModelParams. In rare cases, it might happen that create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld determines a value for the number of pyramid levels that is too large or too small. If the number of pyramid levels is chosen too large, the model may not be recognized in the image or it may be necessary to select very low parameters for MinScore or Greediness in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel in order to find the model. If the number of pyramid levels is chosen too small, the time required to find the model in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel may increase. In these cases, the number of pyramid levels should be selected manually.

AngleStart, AngleExtent and AngleStep:

The parameters AngleStartAngleStartAngleStartAngleStartangleStart and AngleExtentAngleExtentAngleExtentAngleExtentangleExtent determine the range of possible rotations, in which the object can occur in the image. Note that the object can only be found in this range of angles by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. The parameter AngleStepAngleStepAngleStepAngleStepangleStep determines the step length within the selected range of angles. Hence, if subpixel accuracy is not specified in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, this parameter specifies the accuracy that is achievable for the angles in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. AngleStepAngleStepAngleStepAngleStepangleStep should be chosen based on the size of the object. Smaller models do not have many different discrete rotations in the image, and hence AngleStepAngleStepAngleStepAngleStepangleStep should be chosen larger for smaller models. If AngleExtentAngleExtentAngleExtentAngleExtentangleExtent is not an integer multiple of AngleStepAngleStepAngleStepAngleStepangleStep, AngleStepAngleStepAngleStepAngleStepangleStep is modified accordingly. To ensure that for model instances without rotation angle values of exactly 0.0 are returned by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, the range of possible rotations is modified as follows: If there is no positive integer value n such that AngleStartAngleStartAngleStartAngleStartangleStart plus n times AngleStepAngleStepAngleStepAngleStepangleStep is exactly 0.0, AngleStartAngleStartAngleStartAngleStartangleStart is decreased by up to AngleStepAngleStepAngleStepAngleStepangleStep and AngleExtentAngleExtentAngleExtentAngleExtentangleExtent is increased by AngleStepAngleStepAngleStepAngleStepangleStep.

ScaleRMin, ScaleRMax, ScaleCMin, ScaleCMax, ScaleRStep and ScaleCStep:

The parameters ScaleRMinScaleRMinScaleRMinScaleRMinscaleRMin, ScaleRMaxScaleRMaxScaleRMaxScaleRMaxscaleRMax, ScaleCMinScaleCMinScaleCMinScaleCMinscaleCMin, and ScaleCMaxScaleCMaxScaleCMaxScaleCMaxscaleCMax determine the range of possible anisotropic scales of the object in the row and column direction. A scale of 1 in both scale factors corresponds to the original size of the model. The parameters ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep determine the step length within the selected range of scales. Hence, if subpixel accuracy is not specified in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, these parameters specify the accuracy that is achievable for the scales in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. Like AngleStepAngleStepAngleStepAngleStepangleStep, ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep should be chosen based on the size of the object. If the respective range of scales is not an integer multiple of ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep, ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep are modified accordingly.

To ensure that for model instances that are not scaled scale values of exactly 1.0 are returned by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, the range of possible scales is modified as follows: If there are no positive integer values n and m such that ScaleRMinScaleRMinScaleRMinScaleRMinscaleRMin plus n times ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep is exactly 1.0 and ScaleCMinScaleCMinScaleCMinScaleCMinscaleCMin plus m times ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep is exactly 1.0, ScaleRMinScaleRMinScaleRMinScaleRMinscaleRMin and ScaleCMinScaleCMinScaleCMinScaleCMinscaleCMin are decreased by up to ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep, respectively, and ScaleRMaxScaleRMaxScaleRMaxScaleRMaxscaleRMax and ScaleCMaxScaleCMaxScaleCMaxScaleCMaxscaleCMax are increased such that the range of possible scales is increased by ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep and ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep, respectively.

Note that the transformations are treated internally such that the scalings are applied first, followed by the rotation. Therefore, the model should usually be aligned such that it appears horizontally or vertically in the model image.

Optimization:

For particularly large models, it may be useful to reduce the number of model points by setting OptimizationOptimizationOptimizationOptimizationoptimization to a value different from 'none'"none""none""none""none". If OptimizationOptimizationOptimizationOptimizationoptimization = 'none'"none""none""none""none", all model points are stored. In all other cases, the number of points is reduced according to the value of OptimizationOptimizationOptimizationOptimizationoptimization. If the number of points is reduced, it may be necessary in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel to set the parameter Greediness to a smaller value, e.g., 0.7 or 0.8. For small models, the reduction of the number of model points does not result in a speed-up of the search because in this case usually significantly more potential instances of the model must be examined.

If OptimizationOptimizationOptimizationOptimizationoptimization is set to 'auto'"auto""auto""auto""auto", create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld automatically determines the reduction of the number of model points.

Metric:

The parameter MetricMetricMetricMetricmetric determines the conditions under which the model is recognized in the image.

If MetricMetricMetricMetricmetric = 'use_polarity'"use_polarity""use_polarity""use_polarity""use_polarity", the object in the image and the model must have the same contrast. If, for example, the model is a bright object on a dark background, the object is found only if it is also brighter than the background.

If MetricMetricMetricMetricmetric = 'ignore_global_polarity'"ignore_global_polarity""ignore_global_polarity""ignore_global_polarity""ignore_global_polarity", the object is found in the image also if the contrast reverses globally. In the above example, the object hence is also found if it is darker than the background. The runtime of find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel will increase slightly in this case.

Note that the metrics ('use_polarity'"use_polarity""use_polarity""use_polarity""use_polarity" and 'ignore_global_polarity'"ignore_global_polarity""ignore_global_polarity""ignore_global_polarity""ignore_global_polarity") can only be selected if all ContoursContoursContoursContourscontours provide the attribute 'edge_direction'"edge_direction""edge_direction""edge_direction""edge_direction", which defines the polarity of the edges. This attribute is available for contours created, e.g., with edges_sub_pixedges_sub_pixEdgesSubPixEdgesSubPixEdgesSubPix with the parameter MethodMethodMethodMethodmethod set to, e.g., 'canny'"canny""canny""canny""canny". Otherwise, these two metrics can be selected with the operator set_shape_model_metricset_shape_model_metricSetShapeModelMetricSetShapeModelMetricSetShapeModelMetric, which determines the polarity of the edges from an image.

If MetricMetricMetricMetricmetric = 'ignore_local_polarity'"ignore_local_polarity""ignore_local_polarity""ignore_local_polarity""ignore_local_polarity", the model is found even if the contrast changes locally. This mode can, for example, be useful if the object consists of a part with medium gray value, within which either darker or brighter sub-objects lie. Since in this case the runtime of find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel increases significantly, it is usually better to create several models that reflect the possible contrast variations of the object with create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld, and to match them simultaneously with find_aniso_shape_modelsfind_aniso_shape_modelsFindAnisoShapeModelsFindAnisoShapeModelsFindAnisoShapeModels.

The above three metrics can only be applied to single-channel images. If a multichannel image is used as the model image or as the search image, only the first channel will be used (and no error message will be returned).

If MetricMetricMetricMetricmetric = 'ignore_color_polarity'"ignore_color_polarity""ignore_color_polarity""ignore_color_polarity""ignore_color_polarity", the model is found even if the color contrast changes locally. This is, for example, the case if parts of the object can change their color, e.g., from red to green. In particular, this mode is useful if it is not known in advance in which channels the object is visible. In this mode, the runtime of find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel can also increase significantly. The metric 'ignore_color_polarity'"ignore_color_polarity""ignore_color_polarity""ignore_color_polarity""ignore_color_polarity" can be used for images with an arbitrary number of channels. If it is used for single-channel images it has the same effect as 'ignore_local_polarity'"ignore_local_polarity""ignore_local_polarity""ignore_local_polarity""ignore_local_polarity". It should be noted that for MetricMetricMetricMetricmetric = 'ignore_color_polarity'"ignore_color_polarity""ignore_color_polarity""ignore_color_polarity""ignore_color_polarity" the channels do not need to contain a spectral subdivision of the light (like in an RGB image). The channels can, for example, also contain images of the same object that were obtained by illuminating the object from different directions.

Note that the first two metrics ('use_polarity'"use_polarity""use_polarity""use_polarity""use_polarity" and 'ignore_global_polarity'"ignore_global_polarity""ignore_global_polarity""ignore_global_polarity""ignore_global_polarity") can only be selected if all ContoursContoursContoursContourscontours provide the attribute 'edge_direction'"edge_direction""edge_direction""edge_direction""edge_direction", which defines the polarity of the edges. For more information about contour attributes like 'edge_direction'"edge_direction""edge_direction""edge_direction""edge_direction" see get_contour_attrib_xldget_contour_attrib_xldGetContourAttribXldGetContourAttribXldGetContourAttribXld. Otherwise, these two metrics can be selected with the operator set_shape_model_metricset_shape_model_metricSetShapeModelMetricSetShapeModelMetricSetShapeModelMetric, which determines the polarity of the edges from an image.

MinContrast:

With MinContrastMinContrastMinContrastMinContrastminContrast, it can be determined which contrast the object edges must at least have in the recognition performed by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. In other words, this parameter separates the object from the noise in the image. Therefore, a good choice is the range of gray value changes caused by the noise in the image. If, for example, the gray values fluctuate within a range of 10 gray levels, MinContrastMinContrastMinContrastMinContrastminContrast should be set to 10. If multichannel images are used for the model and the search images, and if the parameter MetricMetricMetricMetricmetric is set to 'ignore_color_polarity'"ignore_color_polarity""ignore_color_polarity""ignore_color_polarity""ignore_color_polarity" (see above) the noise in one channel must be multiplied by the square root of the number of channels to determine MinContrastMinContrastMinContrastMinContrastminContrast. If, for example, the gray values fluctuate within a range of 10 gray levels in a single channel and the image is a three-channel image MinContrastMinContrastMinContrastMinContrastminContrast should be set to 17. If the model should be recognized in very low contrast images, MinContrastMinContrastMinContrastMinContrastminContrast must be set to a correspondingly small value. If the model should be recognized even if it is severely occluded, MinContrastMinContrastMinContrastMinContrastminContrast should be slightly larger than the range of gray value fluctuations created by noise in order to ensure that the position and rotation of the model are extracted robustly and accurately by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel.

Complete pregeneration of the model

Optionally, a second value can be passed in OptimizationOptimizationOptimizationOptimizationoptimization. This value determines whether the model is pregenerated completely or not. To do so, the second value of OptimizationOptimizationOptimizationOptimizationoptimization must be set to either 'pregeneration'"pregeneration""pregeneration""pregeneration""pregeneration" or 'no_pregeneration'"no_pregeneration""no_pregeneration""no_pregeneration""no_pregeneration". If the second value is not used (i.e., if only one value is passed), the mode that is set with set_system('pregenerate_shape_models',...)set_system("pregenerate_shape_models",...)SetSystem("pregenerate_shape_models",...)SetSystem("pregenerate_shape_models",...)SetSystem("pregenerate_shape_models",...) is used. With the default value ('pregenerate_shape_models'"pregenerate_shape_models""pregenerate_shape_models""pregenerate_shape_models""pregenerate_shape_models" = 'false'"false""false""false""false"), the model is not pregenerated completely. The complete pregeneration of the model normally leads to slightly lower runtimes because the model does not need to be transformed at runtime. However, in this case, the memory requirements and the time required to create the model are significantly higher. It should also be noted that it cannot be expected that the two modes return exactly identical results because transforming the model at runtime necessarily leads to different internal data for the transformed models than pregenerating the transformed models. For example, if the model is not pregenerated completely, find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel typically returns slightly lower scores, which may require setting a slightly lower value for MinScore than for a completely pregenerated model. Furthermore, the poses obtained by interpolation may differ slightly in the two modes. If maximum accuracy is desired, the pose of the model should be determined by least-squares adjustment.

If a complete pregeneration of the model is selected, the model is pregenerated for the selected angle and scale range and stored in memory. The memory required to store the model is proportional to the number of angle steps, the number of scale steps, and the number of points in the model. Hence, if AngleStepAngleStepAngleStepAngleStepangleStep, ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep, or ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep are too small or AngleExtentAngleExtentAngleExtentAngleExtentangleExtent or the range of scales are too big, it may happen that the model no longer fits into the (virtual) memory. In this case, AngleStepAngleStepAngleStepAngleStepangleStep, ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep, or ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep must be enlarged or AngleExtentAngleExtentAngleExtentAngleExtentangleExtent or the range of scales must be reduced. In any case, it is desirable that the model completely fits into the main memory, because this avoids paging by the operating system, and hence the time to find the object will be much smaller. Since angles can be determined with subpixel resolution by find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, AngleStepAngleStepAngleStepAngleStepangleStep >= 1° and ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep, ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep >= 0.02 can be selected for models of a diameter smaller than about 200 pixels.

If AngleStepAngleStepAngleStepAngleStepangleStep = 'auto'"auto""auto""auto""auto" or ScaleRStepScaleRStepScaleRStepScaleRStepscaleRStep, ScaleCStepScaleCStepScaleCStepScaleCStepscaleCStep = 'auto'"auto""auto""auto""auto" is selected, create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld automatically determines a suitable angle or scale step length, respectively, based on the size of the model. The automatically computed angle and scale step lengths can be queried using get_shape_model_paramsget_shape_model_paramsGetShapeModelParamsGetShapeModelParamsGetShapeModelParams.

If a complete pregeneration of the model is not selected, the model is only created in a reference pose on each pyramid level. In this case, the model must be transformed to the different angles and scales at runtime in find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel. Because of this, the recognition of the model might require slightly more time.

Note that pregenerated shape models are tailored to a specific image size. For runtime reasons using images of different sizes during the search with the same model in parallel is not supported. In this case, copies of the same model must be used, otherwise the program may crash!

Attention

The XLD contours passed in ContoursContoursContoursContourscontours should have been scaled to approximately the average size of the object in the search images. This means that the products and should be approximately equal to 1.

Note that, in contrast to the operator create_aniso_shape_modelcreate_aniso_shape_modelCreateAnisoShapeModelCreateAnisoShapeModelCreateAnisoShapeModel, it is not possible to specify a minimum size of the model components. To avoid small model components in the shape model, short contours can be eliminated before calling create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld with the operator select_contours_xldselect_contours_xldSelectContoursXldSelectContoursXldSelectContoursXld.

Execution Information

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Processed without parallelization.

This operator returns a handle. Note that the state of an instance of this handle type may be changed by specific operators even though the handle is used as an input parameter by those operators.

Parameters

Result

If the parameters are valid, the operator create_aniso_shape_model_xldcreate_aniso_shape_model_xldCreateAnisoShapeModelXldCreateAnisoShapeModelXldCreateAnisoShapeModelXld returns the value 2 (H_MSG_TRUE). If necessary an exception is raised. If the parameter NumLevelsNumLevelsNumLevelsNumLevelsnumLevels is chosen such that the model contains too few points, the error 8510 is raised.

Possible Predecessors

read_contour_xld_dxfread_contour_xld_dxfReadContourXldDxfReadContourXldDxfReadContourXldDxf, edges_sub_pixedges_sub_pixEdgesSubPixEdgesSubPixEdgesSubPix, select_contours_xldselect_contours_xldSelectContoursXldSelectContoursXldSelectContoursXld

Possible Successors

find_aniso_shape_modelfind_aniso_shape_modelFindAnisoShapeModelFindAnisoShapeModelFindAnisoShapeModel, find_aniso_shape_modelsfind_aniso_shape_modelsFindAnisoShapeModelsFindAnisoShapeModelsFindAnisoShapeModels, get_shape_model_paramsget_shape_model_paramsGetShapeModelParamsGetShapeModelParamsGetShapeModelParams, clear_shape_modelclear_shape_modelClearShapeModelClearShapeModelClearShapeModel, write_shape_modelwrite_shape_modelWriteShapeModelWriteShapeModelWriteShapeModel, set_shape_model_originset_shape_model_originSetShapeModelOriginSetShapeModelOriginSetShapeModelOrigin, set_shape_model_paramset_shape_model_paramSetShapeModelParamSetShapeModelParamSetShapeModelParam, set_shape_model_metricset_shape_model_metricSetShapeModelMetricSetShapeModelMetricSetShapeModelMetric

Alternatives

create_shape_model_xldcreate_shape_model_xldCreateShapeModelXldCreateShapeModelXldCreateShapeModelXld, create_scaled_shape_model_xldcreate_scaled_shape_model_xldCreateScaledShapeModelXldCreateScaledShapeModelXldCreateScaledShapeModelXld

See also

set_systemset_systemSetSystemSetSystemSetSystem, get_systemget_systemGetSystemGetSystemGetSystem

Module

Matching