Dot¶

class Dot(*args, **kwargs)¶

Bases: Tracker

This tracker is meant to track a dot (connected pixels with same gray level) on a vpImage .

The underground algorithm is based on a binarization of the image and a connex component segmentation to determine the dot characteristics (location, moments, size…).

The following sample code shows how to grab images from a firewire camera, track a blob and display the tracking results.

#include <visp3/blob/vpDot.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/sensor/vp1394TwoGrabber.h>

int main()
{
#if defined(VISP_HAVE_DC1394)
  vpImage<unsigned char> I; // Create a gray level image container
  vp1394TwoGrabber g(false); // Create a grabber based on libdc1394-2.x third party lib
  g.acquire(I); // Acquire an image

#if defined(VISP_HAVE_X11)
  vpDisplayX d(I, 0, 0, "Camera view");
#endif
  vpDisplay::display(I);
  vpDisplay::flush(I);

  vpDot blob;
  blob.initTracking(I);
  blob.setGraphics(true);

  while(1) {
    g.acquire(I); // Acquire an image
    vpDisplay::display(I);
    blob.track(I);

    vpDisplay::flush(I);
  }
#endif
}

Note

See vpDot2

Overloaded function.

__init__(self: visp._visp.blob.Dot) -> None
__init__(self: visp._visp.blob.Dot, ip: visp._visp.core.ImagePoint) -> None

Constructor with initialization of the dot location.

Parameters:

ip: An image point with sub-pixel coordinates.

__init__(self: visp._visp.blob.Dot, d: visp._visp.blob.Dot) -> None

Copy constructor.

Methods

`__init__`	Overloaded function.
`display`	Display in overlay the dot edges and center of gravity.
`displayDot`	Overloaded function.
`getArea`	Gets the area of the blob corresponding also to the zero order moment.
`getBBox`	Return the dot bounding box.
`getCog`	Return the location of the dot center of gravity.
`getConnexities`	Return the list of all the image points inside the dot.
`getEdges`	Return the list of all the image points on the border of the dot.
`getGamma`
`getGrayLevelPrecision`	Return the precision of the gray level of the dot.
`getHeight`	Return the width of the dot.
`getMaxDotSize`
`getMeanGrayLevel`	Return the mean gray level value of the dot.
`getPolygon`	return: a vpPolygon made from the edges of the dot.
`getWidth`	Return the width of the dot.
`get_nij`	Gets the second order normalized centered moment \(n_{ij}\) as a 3-dim vector containing \(n_{20}, n_{11}, n_{02}\) such as \(n_{ij} = \mu_{ij}/m_{00}\)
`initTracking`	Overloaded function.
`print`
`setCog`	Initialize the dot coordinates with ip .
`setComputeMoments`	Activates the dot's moments computation.
`setConnexity`	Set the type of connexity: 4 or 8.
`setGraphics`	Activates the display of all the pixels of the dot during the tracking.
`setGraphicsThickness`	Modify the default thickness that is set to 1 of the drawings in overlay when setGraphics() is enabled.
`setGrayLevelMax`
`setGrayLevelMin`
`setGrayLevelPrecision`	Set the precision of the gray level of the dot.
`setMaxDotSize`	Maximal size of the region to track in terms of image size percentage.
`track`	Overloaded function.

Inherited Methods

`get_p`	Return object parameters expressed in the 2D image plane computed by perspective projection.
`get_cP`	Return object parameters expressed in the 3D camera frame.
`cP`
`p`
`cPAvailable`

Operators

`__doc__`
`__eq__`
`__hash__`
`__init__`	Overloaded function.
`__module__`
`__ne__`
`__repr__`

Attributes

`CONNEXITY_4`
`CONNEXITY_8`
`__annotations__`
`__hash__`
`cP`
`cPAvailable`
`p`

class ConnexityType(self, value: int)¶

Bases: pybind11_object

Type of connexity 4, or 8.

Values:

CONNEXITY_4: For a given pixel 4 neighbors are considered (left, right, up, down)
CONNEXITY_8: For a given pixel 8 neighbors are considered (left, right, up, down, and the 4 pixels located on the diagonal)

__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¶

__eq__(self, d: visp._visp.blob.Dot) → bool¶

__init__(*args, **kwargs)¶

Overloaded function.

__init__(self: visp._visp.blob.Dot) -> None
__init__(self: visp._visp.blob.Dot, ip: visp._visp.core.ImagePoint) -> None

Constructor with initialization of the dot location.

Parameters:

ip: An image point with sub-pixel coordinates.

__init__(self: visp._visp.blob.Dot, d: visp._visp.blob.Dot) -> None

Copy constructor.

__ne__(self, d: visp._visp.blob.Dot) → bool¶

display(self, I: visp._visp.core.ImageGray, color: visp._visp.core.Color, thickness: int = 1) → None¶

Display in overlay the dot edges and center of gravity.

Parameters:

I: visp._visp.core.ImageGray¶: Image.
color: visp._visp.core.Color¶: The color used for the display.

static displayDot(*args, **kwargs)¶

Overloaded function.

displayDot(I: visp._visp.core.ImageGray, cog: visp._visp.core.ImagePoint, edges_list: list[visp._visp.core.ImagePoint], color: visp._visp.core.Color, thickness: int = 1) -> None

Display the dot center of gravity and its list of edges.

Parameters:

I: The image used as background.
cog: The center of gravity.
edges_list: The list of edges;
color: Color used to display the dot.
thickness: Thickness of the dot.

displayDot(I: visp._visp.core.ImageRGBa, cog: visp._visp.core.ImagePoint, edges_list: list[visp._visp.core.ImagePoint], color: visp._visp.core.Color, thickness: int = 1) -> None

Display the dot center of gravity and its list of edges.

Parameters:

I: The image used as background.
cog: The center of gravity.
edges_list: The list of edges;
color: Color used to display the dot.
thickness: Thickness of the dot.

getArea(self) → float¶

Gets the area of the blob corresponding also to the zero order moment.

Returns:: The blob area.

getBBox(self) → visp._visp.core.Rect¶: Return the dot bounding box.

Note

See getWidth() , getHeight()

getCog(self) → visp._visp.core.ImagePoint¶

Return the location of the dot center of gravity.

Returns:: The coordinates of the center of gravity.

getConnexities(self) → list[visp._visp.core.ImagePoint]¶

Return the list of all the image points inside the dot.

Returns:: The list of all the images points in the dot. This list is updated after a call to track() .

getEdges(self) → list[visp._visp.core.ImagePoint]¶: Return the list of all the image points on the border of the dot.

Warning

Doesn’t return the image points inside the dot anymore. To get those points see getConnexities() .

getGamma(self) → float¶

getGrayLevelPrecision(self) → float¶: Return the precision of the gray level of the dot. It is a double precision float witch value is in ]0,1]. 1 means full precision, whereas values close to 0 show a very bad precision.

getHeight(self) → int¶: Return the width of the dot.

Note

See getHeight()

getMaxDotSize(self) → float¶

getMeanGrayLevel(self) → float¶: Return the mean gray level value of the dot.

getPolygon(self) → visp._visp.core.Polygon¶

Returns:: a vpPolygon made from the edges of the dot.

getWidth(self) → int¶: Return the width of the dot.

Note

See getHeight()

get_cP(self) → visp._visp.core.ColVector¶: Return object parameters expressed in the 3D camera frame.

get_nij(self) → visp._visp.core.ColVector¶

Gets the second order normalized centered moment \(n_{ij}\) as a 3-dim vector containing \(n_{20}, n_{11}, n_{02}\) such as \(n_{ij} = \mu_{ij}/m_{00}\)

Note

See getCog() , getArea()

Returns:: The 3-dim vector containing \(n_{20}, n_{11}, n_{02}\) .

get_p(self) → visp._visp.core.ColVector¶: Return object parameters expressed in the 2D image plane computed by perspective projection.

initTracking(*args, **kwargs)¶

Overloaded function.

initTracking(self: visp._visp.blob.Dot, I: visp._visp.core.ImageGray) -> None

Initialize the tracking with a mouse click and update the dot characteristics (center of gravity, moments).

Wait a user click in a gray area in the image I. The clicked pixel will be the starting point from which the dot will be tracked.

The threshold used to segment the dot is set with the grayLevelPrecision parameter. See the formula in setGrayLevelPrecision() function.

The sub pixel coordinates of the dot are updated. To get the center of gravity coordinates of the dot, use getCog() . To compute the moments use setComputeMoments(true) before a call to initTracking() .

Warning

The content of the image modified since we call track() to compute the dot characteristics.

Note

See track() , getCog()

Parameters:

I: Image to process.

initTracking(self: visp._visp.blob.Dot, I: visp._visp.core.ImageGray, ip: visp._visp.core.ImagePoint) -> None

Initialize the tracking for a dot supposed to be located at (u,v) and updates the dot characteristics (center of gravity, moments).

The threshold used to segment the dot is set to 80 percent of the gray level of the pixel (u,v).

Warning

The content of the image modified since we call track() to compute the dot characteristics.

Note

See track()

Parameters:

I: Image to process.
ip: Location of the starting point from which the dot will be tracked in the image.

initTracking(self: visp._visp.blob.Dot, I: visp._visp.core.ImageGray, ip: visp._visp.core.ImagePoint, gray_level_min: int, gray_level_max: int) -> None

Initialize the tracking for a dot supposed to be located at (u,v) and updates the dot characteristics (center of gravity, moments).

Warning

The content of the image modified since we call track() to compute the dot characteristics.

Note

See track() , getCog()

Parameters:

I: Image to process.
ip: Location of the starting point from which the dot will be tracked in the image.

print(self: visp._visp.blob.Dot, os: std::ostream) → None¶

setCog(self, ip: visp._visp.core.ImagePoint) → None¶: Initialize the dot coordinates with ip .

setComputeMoments(self, activate: bool) → None¶

Activates the dot’s moments computation.

Computed moment are vpDot::m00 , vpDot::m10 , vpDot::m01 , vpDot::m11 , vpDot::m20 , vpDot::m02 and second order centered moments vpDot::mu11 , vpDot::mu20 , vpDot::mu02 computed with respect to the blob centroid.

The coordinates of the region’s centroid (u, v) can be computed from the moments by \(u=\frac{m10}{m00}\) and \(v=\frac{m01}{m00}\) .

Parameters:

activate: bool¶: true, if you want to compute the moments. If false, moments are not computed.

setConnexity(self, type: visp._visp.blob.Dot.ConnexityType) → None¶: Set the type of connexity: 4 or 8.

setGraphics(self, activate: bool) → None¶

Activates the display of all the pixels of the dot during the tracking. The default thickness of the overlayed drawings can be modified using setGraphicsThickness() .

Warning

To effectively display the dot graphics a call to vpDisplay::flush() is needed.

Note

See setGraphicsThickness()

Parameters:

activate: bool¶: true to activate the display of dot pixels, false to turn off the display.

setGraphicsThickness(self, t: int) → None¶: Modify the default thickness that is set to 1 of the drawings in overlay when setGraphics() is enabled.

Note

See setGraphics()

setGrayLevelMax(self, level_max: int) → None¶

setGrayLevelMin(self, level_min: int) → None¶

setGrayLevelPrecision(self, grayLevelPrecision: float) → None¶: Set the precision of the gray level of the dot.

Note

See setWidth(), setHeight(), setGrayLevelMin() , setGrayLevelMax()

setMaxDotSize(self, percentage: float) → None¶

Maximal size of the region to track in terms of image size percentage.

During the tracking, if the dot size if bigger than the maximal size allowed an exception is throwed : vpTrackingException::featureLostError .

Parameters:

percentage: float¶: Image size percentage corresponding to the dot maximal size. Values should be in ]0 : 1]. If 1, that means that the dot to track could take up the whole image.

track(*args, **kwargs)¶

Overloaded function.

track(self: visp._visp.blob.Dot, I: visp._visp.core.ImageGray) -> None

Track and compute the dot characteristics.

To get the center of gravity coordinates of the dot, use getCog() . To compute the moments use setComputeMoments(true) before a call to initTracking() .

Warning

The image is modified (all the pixels that belong to the point are set to white (ie to 255).

Note

See getCog()

Parameters:

I: Image to process.

track(self: visp._visp.blob.Dot, I: visp._visp.core.ImageGray, ip: visp._visp.core.ImagePoint) -> None

Track and updates the new dot coordinates

To compute the moments use setComputeMoments(true) before a call to initTracking() or track() .

Warning

The image is modified (all the pixels that belong to the point are set to white (ie to 255).

Parameters:

I: Image to process.
ip: [out] : Sub pixel coordinate of the tracked dot center of gravity.

__hash__ = None¶