FeatureMomentCInvariant¶

class FeatureMomentCInvariant¶

Bases: FeatureMoment

Functionality computation for 2D rotation/translation/scale non-symmetric invariant moment feature. Computes the interaction matrix associated with vpMomentCInvariant .

The interaction matrix for the moment feature can be deduced from [40] , equations (9). To do so, one must derive them and obtain a combination of interaction matrices by using (1). It allows to compute the interaction matrix for \(c_i, i \in [1..10]\) .

These interaction matrices may be selected afterwards by calling vpFeatureMomentCInvariant::interaction() . The selection by the vpFeatureMomentCInvariant::selectCi method for \(L_{c_i}\) . For example, to select \(L_{c_1}\) you should input vpFeatureMomentCInvariant::selectC1() into ViSP’s selector. Special matrices for features \(S_x\) and \(S_y\) are selected by vpFeatureMomentCInvariant::selectSx() and vpFeatureMomentCInvariant::selectSy() respectively. Special matrices for features \(P_x\) and \(P_y\) are selected by vpFeatureMomentCInvariant::selectPx() and vpFeatureMomentCInvariant::selectPy() respectively.

These features are often used in moment-based visual servoing to control the two out-of-plane rotations.

Be careful about the nature of your object when selecting the right features. Use \(L_{S_{x}}\) and \(L_{S_{y}}\) when you’re dealing with a symmetric object all other features otherwise.

Minimum vpMomentObject order needed to compute this feature: 6. This is the highest order required by classic features.

This feature depends on:

vpMomentCentered
vpFeatureMomentCentered
vpMomentCInvariant
vpFeatureMomentBasic

An example of how to use vpFeatureMomentCInvariant in a complete visual servoing example is given in vpFeatureMomentCommon .

Methods

`__init__`
`compute_interaction`	Overloaded function.
`momentName`	Associated moment name.
`name`	Feature name.
`printLsofInvariants`	Print all the interaction matrices of the moment invariants
`selectC1`	Shortcut selector for \(C_1\) .
`selectC10`	Shortcut selector for \(C_{10}\) .
`selectC2`	Shortcut selector for \(C_2\) .
`selectC3`	Shortcut selector for \(C_3\) .
`selectC4`	Shortcut selector for \(C_4\) .
`selectC5`	Shortcut selector for \(C_5\) .
`selectC6`	Shortcut selector for \(C_6\) .
`selectC7`	Shortcut selector for \(C_7\) .
`selectC8`	Shortcut selector for \(C_8\) .
`selectC9`	Shortcut selector for \(C_9\) .
`selectPx`	Shortcut selector for \(P_x\) .
`selectPy`	Shortcut selector for \(P_y\) .
`selectSx`	Shortcut selector for \(S_x\) .
`selectSy`	Shortcut selector for \(S_y\) .

Inherited Methods

`user`
`BasicFeatureSelect`	Indicates who should deallocate the feature.
`error`	Compute the error between two visual features from a subset of the possible features.
`setFlags`	Set feature flags to true to prevent warning when re-computing the interaction matrix without having updated the feature.
`FEATURE_ALL`
`getDimension`	Overloaded function.
`linkTo`	Links the feature to the feature's database.
`getDeallocate`
`init`	Initialize common parameters for moment features.
`interaction`	Retrieves the interaction matrix.
`dimension_s`	Return the dimension of the feature vector \(\bf s\) .
`setDeallocate`
`selectAll`	Select all the features.
`printDependencies`	Interface function to display the moments and other interaction matrices on which a particular vpFeatureMoment is dependent upon Not made pure to maintain compatibility Recommended : Types inheriting from vpFeatureMoment should implement this function.
`display`	Overloaded function.
`update`	Updates the interaction matrices with the image plane the camera is facing.
`get_s`	Get the feature vector \(\bf s\) .
`BasicFeatureDeallocatorType`	Indicates who should deallocate the feature.
`vpServo`
`print`	Outputs the content of the feature: it's corresponding selected moments.

Operators

`__doc__`
`__init__`
`__module__`
`__repr__`

Attributes

`FEATURE_ALL`
`__annotations__`
`user`
`vpServo`

class BasicFeatureDeallocatorType(self, value: int)¶

Bases: pybind11_object

Indicates who should deallocate the feature.

Values:

user
vpServo

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

class BasicFeatureSelect(self, value: int)¶

Bases: pybind11_object

Indicates who should deallocate the feature.

Values:

user
vpServo

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

__init__(*args, **kwargs)¶

compute_interaction(*args, **kwargs)¶

Overloaded function.

compute_interaction(self: visp._visp.visual_features.FeatureMomentCInvariant) -> None

Computes interaction matrix for space-scale-rotation invariants. Called internally. The moment primitives must be computed before calling this. This feature depends on:

vpMomentCentered
vpFeatureMomentCentered
vpMomentCInvariant
vpFeatureMomentBasic

compute_interaction(self: visp._visp.visual_features.FeatureMoment) -> None

dimension_s(self) → int¶: Return the dimension of the feature vector \(\bf s\) .

display(*args, **kwargs)¶

Overloaded function.

display(self: visp._visp.visual_features.FeatureMoment, cam: visp._visp.core.CameraParameters, I: visp._visp.core.ImageGray, color: visp._visp.core.Color = vpColor::green, thickness: int = 1) -> None

Not implemented since visual representation of a moment doesn’t often make sense.

display(self: visp._visp.visual_features.FeatureMoment, cam: visp._visp.core.CameraParameters, I: visp._visp.core.ImageRGBa, color: visp._visp.core.Color = vpColor::green, thickness: int = 1) -> None

Not implemented since visual representation of a moment doesn’t often make sense.

error(self, s_star: visp._visp.visual_features.BasicFeature, select: int = FEATURE_ALL) → visp._visp.core.ColVector¶: Compute the error between two visual features from a subset of the possible features.

getDeallocate(self) → visp._visp.visual_features.BasicFeature.BasicFeatureDeallocatorType¶

getDimension(*args, **kwargs)¶

Overloaded function.

getDimension(self: visp._visp.visual_features.FeatureMoment, select: int = FEATURE_ALL) -> int

Feature’s dimension according to selection.

getDimension(self: visp._visp.visual_features.BasicFeature, select: int = FEATURE_ALL) -> int

Get the feature vector dimension.

get_s(self, select: int = FEATURE_ALL) → visp._visp.core.ColVector¶: Get the feature vector \(\bf s\) .

init(self) → None¶: Initialize common parameters for moment features.

interaction(self, select: int = FEATURE_ALL) → visp._visp.core.Matrix¶

Retrieves the interaction matrix. No computation is done.

There is no rule about the format of the feature selector. It may be different for different features. For example, for vpFeatureMomentBasic or vpFeatureMomentCentered features, select may refer to the \((i,j)\) couple in the \(j \times order + i\) format, but for vpFeatureMomentCInvariant the selector allows to select couples \((i,j,k,l...)\) in the following format: 1 << i

1 << j + 1 << k + 1 << l.

Parameters:

select: int = FEATURE_ALL¶: Feature selector.

Returns:

The corresponding interaction matrix.

linkTo(self, featureMoments: visp._visp.visual_features.FeatureMomentDatabase) → None¶

Links the feature to the feature’s database.

Note

The feature’s database is different from the moment’s database.

Parameters:

featureMoments: visp._visp.visual_features.FeatureMomentDatabase¶: database in which the moment features are stored.

momentName(self) → str¶: Associated moment name.

name(self) → str¶: Feature name.

print(self, select: int = FEATURE_ALL) → None¶: Outputs the content of the feature: it’s corresponding selected moments.

printDependencies(self: visp._visp.visual_features.FeatureMoment, os: std::ostream) → None¶: Interface function to display the moments and other interaction matrices on which a particular vpFeatureMoment is dependent upon Not made pure to maintain compatibility Recommended : Types inheriting from vpFeatureMoment should implement this function.

printLsofInvariants(self: visp._visp.visual_features.FeatureMomentCInvariant, os: std::ostream) → None¶

Print all the interaction matrices of the moment invariants

Print out all invariants that were computed There are 15 of them, as in [Point-based and region based.ITRO05] [40]

static selectAll() → int¶: Select all the features.

static selectC1() → int¶: Shortcut selector for \(C_1\) .

static selectC10() → int¶: Shortcut selector for \(C_{10}\) .

static selectC2() → int¶: Shortcut selector for \(C_2\) .

static selectC3() → int¶: Shortcut selector for \(C_3\) .

static selectC4() → int¶: Shortcut selector for \(C_4\) .

static selectC5() → int¶: Shortcut selector for \(C_5\) .

static selectC6() → int¶: Shortcut selector for \(C_6\) .

static selectC7() → int¶: Shortcut selector for \(C_7\) .

static selectC8() → int¶: Shortcut selector for \(C_8\) .

static selectC9() → int¶: Shortcut selector for \(C_9\) .

static selectPx() → int¶: Shortcut selector for \(P_x\) .

static selectPy() → int¶: Shortcut selector for \(P_y\) .

static selectSx() → int¶: Shortcut selector for \(S_x\) .

static selectSy() → int¶: Shortcut selector for \(S_y\) .

setDeallocate(self, d: visp._visp.visual_features.BasicFeature.BasicFeatureDeallocatorType) → None¶

setFlags(self) → None¶: Set feature flags to true to prevent warning when re-computing the interaction matrix without having updated the feature.

update(self, A: float, B: float, C: float) → None¶

Updates the interaction matrices with the image plane the camera is facing. The plane must be in the format: \(\frac{1}{Z}=Ax+By+C\) . The moment primitives MUST be updated before calling this function.

This method also computes the interaction matrix. Therefore, you must call vpFeatureMoment::update before calling vpFeatureMoment::interaction .

Warning

The behaviour of this method is not the same as vpMoment::update which only acknowledges the new object. This method also computes the interaction matrices.