find_component_model — Find the best matches of a component model in an image.
find_component_model(Image : : ComponentModelID, RootComponent, AngleStartRoot, AngleExtentRoot, MinScore, NumMatches, MaxOverlap, IfRootNotFound, IfComponentNotFound, PosePrediction, MinScoreComp, SubPixelComp, NumLevelsComp, GreedinessComp : ModelStart, ModelEnd, Score, RowComp, ColumnComp, AngleComp, ScoreComp, ModelComp)
The operator find_component_model finds the best
NumMatches instances of the component model
ComponentModelID in the input image Image.
The result of the search can be visualized using
get_found_component_model.
Also the operator can be used to extract the component matches
of a certain component model instance.
ComponentModelID:Handle of the component model.
The model must have been created previously by calling
create_trained_component_model or
create_component_model, or read in using
read_component_model.
RootComponent:Index of the root component.
The components of the component model ComponentModelID are
represented in in a tree structure. The component that stands at the
root of this search tree is the root component.
The root component is searched within the full search space, i.e., at all allowed positions and in the allowed range of orientations (see below). In contrast, the remaining components are searched relative to the pose of their predecessor in the search tree within a restricted search space that is computed from the relations (recursive search).
To what extent a model component is suited to act as root component depends
on several factors. In principle, a model component that can be found
in the image with a high probability, should be chosen. Therefore, a
component that is sometimes occluded to a high degree or that is
missing in some cases is not well suited to act as root
component.
For the behavior in such cases, see the entry IfRootNotFound
below.
A different possible criterion is the computation time
that is associated with the root component during the search.
A ranking of the model components that is
based on the latter criterion is returned in RootRanking
of the operator create_trained_component_model or
create_component_model, respectively.
If the complete ranking is passed in RootComponent,
the first value RootComponent[0] is automatically selected
as the root component.
AngleStartRoot and AngleExtentRoot:Specify the allowed angle range (in [rad]) within which the root component is searched.
If necessary, the range of rotations
is clipped to the range given when the component model was created
with create_trained_component_model or
create_component_model, respectively.
The angle range for each component can be queried with
get_shape_model_params.
The necessary handle of the corresponding shape model can be obtained using
get_component_model_params.
MinScore:Determines what score a potential match of the component model must at least have to be regarded as an instance.
If the component model can be expected never to be occluded in the images,
MinScore may be set as high as 0.8 or even 0.9.
The value of this parameter only slightly influences the computation time.
An exception is the case of IfRootNotFound set to
'select_new_root' (see below).
NumMatches:Determines the maximum number of returned instances.
If fewer than NumMatches are found, only that number is
returned, i.e., the parameter MinScore takes precedence
over NumMatches.
In case more than NumMatches instances with a score greater than
MinScore are found in the image, only the best
NumMatches instances are returned.
However, if all model instances exceeding MinScore in the image
should be found, NumMatches must be set to 0.
MaxOverlap:Determines by what fraction two instances may at most overlap, whereby this fraction is a number between 0 and 1.
In some cases, found instances only differ in the pose of one or a few
components.
If two instances overlap each other by more than
MaxOverlap only the best instance is returned.
This means, for MaxOverlap = 0, the found instances may
not overlap at all, while for MaxOverlap = 1 no check for
overlap is performed, and hence all instances are returned.
The calculation of the overlap is based on the smallest enclosing
rectangles of arbitrary orientation (see smallest_rectangle2)
of the found component instances.
IfRootNotFound:specifies the behavior of the operator when dealing with a missing or strongly occluded root component.
Possible values:
'stop_search': It is assumed that the root component is always found in the image. Consequently, for instances for which the root component could not be found the search for the remaining components is not continued.
'select_new_root':
Different components are successively chosen as the root component
and searched within the full search space.
The order in which the selection of the root component is performed
corresponds to the order passed in RootRanking.
The poses of the found instances of all root components are then used
to start the recursive search for the remaining components.
Hence, it is possible to find instances even if the original root
component is not found.
However, the computation time of the search increases significantly
in comparison to the search when choosing 'stop_search'.
This is especially the case for small values of MinScore,
as more root components must be searched.
If during the search more root components are needed as given in
RootComponent, the root components are completed by
the automatically computed order
(see create_trained_component_model or
create_component_model).
IfComponentNotFound:Specifies how components are searched when the predecessor component was not found (e.g., because she is missing or strongly occluded).
Possible values:
'prune_branch': Such components are not searched at all and are also treated as 'not found'.
'search_from_upper': Such components are searched relative to the pose of the predecessor component of the predecessor component.
'search_from_best': Such components are searched relative to the pose of the already found component from which the relative search can be performed with minimum computational effort.
PosePrediction:Determines whether the pose of not found components should be estimated.
Possible values:
'none': Only the poses of the found components are returned.
'from_neighbors':
The poses of not found components are estimated and returned with a score
of ScoreComp = 0.0.
The pose estimation is based on the poses of the found neighboring
components in the search tree.
'from_all':
The poses of not found components are estimated and returned with a score
of ScoreComp = 0.0.
The pose estimation is based on the poses of all found components.
MinScoreComp:Minimal necessary score of the components for the instances to be found.
This parameter has the same meaning as MinScore in
find_shape_model.
Settable is either one element or the same number of elements as model
components in ComponentModelID.
In the first case the parameter is used for all components.
In the second case, each parameter element refers to the corresponding
component in ComponentModelID.
SubPixelComp:Determines whether the extraction shall be done subpixel precise and in the given case the maximal allowed object deformation in pixels.
This parameter has the same meaning as SubPixel in
find_shape_model.
Therefore the maximal allowed object deformation has to be given as
integer in the same string.
Settable is either one element or the same number of elements as model
components in ComponentModelID.
In the first case the parameter is used for all components.
In the second case, each parameter element refers to the corresponding
component in ComponentModelID.
Example: ['least_squares', 'max_deformation 2'].
NumLevelsComp:Determine the pyramid levels for the components used in the matching.
This parameter has the same meaning as NumLevels in
find_shape_model.
It determines the number of pyramid levels for the components
to be used in the matching.
Settable is either one element or the same number of elements as model
components in ComponentModelID.
In the first case the parameter is used for all components.
In the second case, each parameter element refers to the corresponding
component in ComponentModelID.
Optional, one can set value pairs for this parameter:
In this case, the first value still determines the number of pyramid levels
to be used.
The second value specifies the lowest pyramid level, to which the found
matches are tracked.
In doing so, one can set either a single value pair or a value pair for each
model component in ComponentModelID.
If different value pairs should be used for different components, they must
be specified in the same tuple.
In case ComponentModelID contains exactly two components and in
NumLevelsComp two values are set, these values are interpreted as
different number of pyramid levels to be used and not as a value pair.
Example: ComponentModelID contains two components, for
which different pyramid levels shall be considered.
For the first component 5 levels up to the level 2 shall be used.
For the second component 4 levels up to the level 1 shall be used.
In this case is NumLevelsComp = [5,2,4,1].
GreedinessComp:“Greediness” of the search heuristic for the components: value from 0 to 1. Thereby 0 means: safe but slow, 1: fast but matches may be missed.
This parameter has the same meaning as Greediness in
find_shape_model.
Settable is either one element or the same number of elements as model
components in ComponentModelID.
In the first case the parameter is used for all components.
In the second case, each parameter element refers to the corresponding
component in ComponentModelID.
ModelStart and ModelEnd:Return the first and last index and therewith the index range of all component matches associated to the same instance of the component model.
The component matches corresponding to the first found instance of the
component model are given by the interval of indices
[ModelStart[0],ModelEnd[0]].
Thereby the indices refer to the values of the parameters RowComp,
ColumnComp, AngleComp, ScoreComp, and
ModelComp.
RowComp = [100,200,300,150,250]
|
ModelStart = [0,3]
|
ColumnComp = [200,210,220,400,425]
|
ModelEnd = [2,4]
|
AngleComp = [0,0.1,-0.2,0.1,0.2]
|
ModelComp = [0,1,2,0,2]
|
ScoreComp = [1,1,1,1,1]
|
Score = [1,1]
|
Values with index 0 to 2 correspond to the components 0 to 2 of instance 1.
Values with index 3 to 4 correspond to the components 0 and 2 of instance 2.
Score:Score of the found instances of the component model.
Score contains the weighted mean of the component scores,
the values in ScoreComp.
The weighting is performed according to the number of model points
within the respective component.
RowComp, ColumnComp, and AngleComp:
The position (RowComp, ColumnComp) and rotation
(AngleComp) of the model components of all found component
model instances.
The coordinates RowComp and ColumnComp are the
coordinates of the component origin (reference poiknt) in
the search image.
The component origin depends on the model creation:
with create_trained_component_model by training:
The component origin is the center of gravity of the respective
returned contour region in ModelComponents of the operator
train_model_components.
with create_component_model manually:
The component origin is the center of gravity of the corresponding
passed component region ComponentRegion of the operator
create_component_model.
Since the relations between the components in ComponentModelID
refer to this reference point, the origin of the components must not be
modified by using set_shape_model_origin.
ScoreComp:Score of each found component instance.
The score is a number between 0 and 1, and is an approximate measure of how much of the component is visible in the image. If, for example, half of the component is occluded, the score cannot exceed 0.5.
ModelComp:Index of the found component.
The tuple contains the indics of the respective model components
(see create_component_model and train_model_components,
respectively).
By this the values in RowComp, ColumnComp,
AngleComp, and ScoreComp can be associated
to the different model components.
See also the example given for ModelStart and ModelEnd.
Internally, the shape-based matching is used for the component-based
matching in order to search the individual components
(see find_shape_model).
The domain of the Image determines the search space for the
reference point, i.e., the allowed positions, of the root component.
Usually the component model is searched only within those points of the
image domain in which the model fits completely into the image.
This means that the components will not be found if they extend beyond the
borders of the image, even if they would achieve a score greater than
MinScoreComp (see above).
Note that, if for a certain pyramid level the component model touches the
image border, it might not be found even if it lies completely within the
original image.
As a rule of thumb, the model might not be found if its distance to
an image border falls below .
This behavior can be changed with
set_system('border_shape_models','true'), which will cause
components that extend beyond the image border to be found if they achieve
a score greater than MinScoreComp.
Here, points lying outside the image are regarded as being occluded, i.e.,
they lower the score.
It should be noted that this mode increases the runtime of the search.
Note further, that in rare cases, which occur typically only for artificial
images, the model might not be found also if for certain pyramid levels the
model touches the border of the reduced domain. Then, it may help to
enlarge the reduced domain by using,
e.g., dilation_circle.
When tracking the matches through the image pyramid, on each level,
some less promising matches are rejected based on NumMatches. Thus,
it is possible that some matches are rejected that would have had a higher
score on the lowest pyramid level. Due to this, for example, the found
match for NumMatches set to 1 might be
different from the match with the highest score returned when setting
NumMatches to 0 or > 1.
If multiple objects with a similar score are expected, but only the one
with the highest score should be returned, it might be preferable to raise
NumMatches, and then select the match with the highest score.
To get a meaningful score value and to avoid erroneous matches,
we recommend to always combine the allowance of a deformation with a
subpixel extraction that applies a least-squares adjustment.
If the subpixel extraction and/or the maximum object deformation is
specified separately for each component, for each component in
ComponentModelID exactly one value for the subpixel extraction
must be passed in SubPixelComp.
After each value for the subpixel extraction optionally a second value can
be passed, which describes the maximum object deformation of the
corresponding mode. If for a certain component no value for the maximum
object deformation is passed, the component is searched without taking
deformations into account.
Further details can be found in the documentation of
find_shape_models.
Image (input_object) (multichannel-)image → object (byte / uint2)
Input image in which the component model should be found.
ComponentModelID (input_control) component_model → (handle)
Handle of the component model.
RootComponent (input_control) integer(-array) → (integer)
Index of the root component.
Suggested values: 0, 1, 2, 3, 4, 5, 6, 7, 8
AngleStartRoot (input_control) angle.rad(-array) → (real)
Smallest rotation of the root component
Default value: -0.39
Suggested values: -3.14, -1.57, -0.79, -0.39, -0.20, 0.0
AngleExtentRoot (input_control) angle.rad(-array) → (real)
Extent of the rotation of the root component.
Default value: 0.79
Suggested values: 6.28, 3.14, 1.57, 0.79, 0.39, 0.0
Restriction: AngleExtentRoot >= 0
MinScore (input_control) real → (real)
Minimum score of the instances of the component model to be found.
Default value: 0.5
Suggested values: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0
Minimum increment: 0.01
Recommended increment: 0.05
Restriction: 0 <= MinScore && MinScore <= 1
NumMatches (input_control) integer → (integer)
Number of instances of the component model to be found (or 0 for all matches).
Default value: 1
Suggested values: 0, 1, 2, 3, 4, 5, 10, 20
MaxOverlap (input_control) real → (real)
Maximum overlap of the instances of the component models to be found.
Default value: 0.5
Suggested values: 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0
Minimum increment: 0.01
Recommended increment: 0.05
Restriction: 0 <= MaxOverlap && MaxOverlap <= 1
IfRootNotFound (input_control) string → (string)
Behavior if the root component is missing.
Default value: 'stop_search'
List of values: 'select_new_root', 'stop_search'
IfComponentNotFound (input_control) string → (string)
Behavior if a component is missing.
Default value: 'prune_branch'
List of values: 'prune_branch', 'search_from_best', 'search_from_upper'
PosePrediction (input_control) string → (string)
Pose prediction of components that are not found.
Default value: 'none'
List of values: 'from_all', 'from_neighbors', 'none'
MinScoreComp (input_control) real(-array) → (real)
Minimum score of the instances of the components to be found.
Default value: 0.5
Suggested values: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0
Minimum increment: 0.01
Recommended increment: 0.05
Restriction: 0 <= MinScoreComp && MinScoreComp <= 1
SubPixelComp (input_control) string(-array) → (string)
Subpixel accuracy of the component poses if not equal to 'none'.
Default value: 'least_squares'
Suggested values: 'none', 'interpolation', 'least_squares', 'least_squares_high', 'least_squares_very_high', 'max_deformation 1', 'max_deformation 2', 'max_deformation 3', 'max_deformation 4', 'max_deformation 5', 'max_deformation 6'
NumLevelsComp (input_control) integer(-array) → (integer)
Number of pyramid levels for the components used in
the matching
(and lowest pyramid level to use if
|NumLevelsComp| = 2n).
Default value: 0
List of values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
GreedinessComp (input_control) real(-array) → (real)
“Greediness” of the search heuristic for the components (0: safe but slow; 1: fast but matches may be missed).
Default value: 0.9
Suggested values: 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0
Minimum increment: 0.01
Recommended increment: 0.05
Restriction: 0 <= GreedinessComp && GreedinessComp <= 1
ModelStart (output_control) integer(-array) → (integer)
Start index of each found instance of the component model in the tuples describing the component matches.
ModelEnd (output_control) integer(-array) → (integer)
End index of each found instance of the component model in the tuples describing the component matches.
Score (output_control) real(-array) → (real)
Score of the found instances of the component model.
RowComp (output_control) point.y(-array) → (real)
Row coordinate of the found component matches.
ColumnComp (output_control) point.x(-array) → (real)
Column coordinate of the found component matches.
AngleComp (output_control) angle.rad(-array) → (real)
Rotation angle of the found component matches.
ScoreComp (output_control) real(-array) → (real)
Score of the found component matches.
ModelComp (output_control) integer(-array) → (integer)
Index of the found components.
If the parameter values are correct, the operator
find_component_model returns the value 2 (H_MSG_TRUE). If the input
is empty (no input image available) the behavior can be set via
set_system('no_object_result',<Result>). If necessary, an
exception is raised.
create_trained_component_model,
create_component_model,
read_component_model
find_shape_model,
find_shape_models,
get_shape_model_params,
get_component_model_params,
train_model_components,
set_shape_model_origin,
smallest_rectangle2
Matching