Gauge Definitions

Point Gauge

You can select the most relevant transition points along a line segment probe that crosses one or several objects edges. Crosswise and lengthwise filtering can be activated for noise reduction.

Point location. Contrast-based selection

Usage

• Define and position the gauge, then fit the points with EPointGauge::Measure ^{.NET Python}.

• Use the methods EPointGauge::GetNumMeasuredPoints ^{.NET Python} and EPointGauge::GetMeasuredPoint ^{.NET Python} to access the results.

Line Gauge

The placement of a ELineGauge ^{.NET Python} is defined by its ELineShape::GetCenter ^{.NET Python}, its ELineShape::GetLength ^{.NET Python} and its ELineShape::GetAngle ^{.NET Python} with respect to the X-axis. To constrain the line slope value, set ELineShape::GetAngle ^{.NET Python} and ELineGauge::GetKnownAngle ^{.NET Python}.

Line fitting

Usage

• Define and position the gauge, then use ELineGauge::Measure ^{.NET Python} to fit the lines.

  • The method EShape::GetFound ^{.NET Python} returns TRUE if a suitable line is found.

  • To obtain the ELine ^{.NET Python}, set the EShape::GetActualShape ^{.NET Python} property to TRUE to return the fitted line (TRUE value) (instead of the nominal line position FALSE value, default).

• Alternatively, ELineGauge::GetMeasuredLine ^{.NET Python} provides the results as an ELine ^{.NET Python} object.

Rectangle Gauge

The placement of a ERectangleGauge ^{.NET Python} is defined by its nominal position (given by the coordinates of its ERectangleShape::GetCenter ^{.NET Python}), its ERectangleShape::SetSize ^{.NET Python} and its ERectangleShape::GetAngle ^{.NET Python}.

Each side of a rectangle can have its own transition detection parameters, and can be set to active or inactive with the ERectangleGauge::GetActiveEdges ^{.NET Python} property. When a side is active:

• Setting the value of a parameter only applies to the currently active sides1.

• Getting the value of a parameter yields a result only when the value of this property is the same for all active sides.

• Only active sides are used for measurement and model fitting.

These rules allow to set different parameters for different sides, and measure parallel sides or a corner point instead of the whole rectangle. The four sides are denoted by letters “x”, “y”, “XX” and “YY” respectively.

Naming conventions for the sides of a rectangle gauge

Usage

• Define and position the gauge, then use ELineGauge::Measure ^{.NET Python} to fit the lines.

  • The method EShape::GetFound ^{.NET Python} returns TRUE if a suitable rectangle is found.

  • To obtain the ERectangleShape ^{.NET Python}, set EShape::GetActualShape ^{.NET Python} to TRUE to return the fitted line (TRUE value) (default is FALSE).

• Alternatively, ERectangleGauge::GetMeasuredRectangle ^{.NET Python} provides the results as an ERectangle ^{.NET Python} object.

• For instance, you can accurately locate the four corners (landmarks) of a rectangle using a rectangle fitting gauge.

Locating a rectangle’s corners

Circle Gauge

The placement of a ECircleGauge ^{.NET Python} is defined by its nominal position (given by the coordinates of its ECircleShape::GetCenter ^{.NET Python}), its nominal ECircleShape::GetDiameter ^{.NET Python} (or ECircleShape::GetRadius ^{.NET Python}), the angular position from where it extends and its angular ECircleShape::GetAmplitude ^{.NET Python}.

The Set member can distinguish between a full circle and an arc (the arc amplitude must be specified).

Circle fitting

Usage

• Once the gauge has been defined and positioned, use ECircleGauge::Measure ^{.NET Python} to trigger the circle fitting operation.

  • The method EShape::GetFound ^{.NET Python} returns TRUE if a suitable rectangle is found.

  • To obtain the measurement results, set the EShape::GetActualShape ^{.NET Python} mode to TRUE. The EShape::GetActualShape ^{.NET Python} mode determines whether an inquiry returns the fitted circle (TRUE value) or the nominal circle position (FALSE value, default).

  • The requested information is then retrieved by means of the ECircleShape ^{.NET Python}.

• Alternatively, ECircleGauge::GetMeasuredCircle ^{.NET Python} provides the results as an ECircle ^{.NET Python} object.

Wedge Gauge

The placement of a EWedgeGauge ^{.NET Python} is defined by its nominal position (given by the coordinates of its EWedgeShape::GetCenter ^{.NET Python}), its nominal EWedgeShape::GetInnerRadius ^{.NET Python} and EWedgeShape::GetOuterRadius ^{.NET Python} (EWedgeShape::GetInnerDiameter ^{.NET Python} and EWedgeShape::GetOuterDiameter ^{.NET Python}), its EWedgeShape::GetBreadth ^{.NET Python} (difference between radii), the EWedgeShape::GetAngle ^{.NET Python} from where it extends and its EWedgeShape::GetAmplitude ^{.NET Python}.

The Set member can distinguish between a full ring, a sector of a ring and a disk.

Each side of a wedge can have its own transition detection parameters and can be set to active or inactive with the EWedgeGauge::GetActiveEdges ^{.NET Python} property. When a side is active, this means that:

• Setting the value of a parameter only applies to the currently active sides;

• Getting the value of a parameter yields a result only when the value of this parameter is the same for all active sides;

• Only active sides are used for measurement and model fitting.

So different sides can have different parameters, and you can measure parallel arcs or oblique sides, or a corner point, instead of the whole wedge. The four sides are denoted by letters “a”, “r”, “AA” and “RR” respectively.

Naming conventions for the sides of a wedge gauge

Usage

• Define and position the gauge, then use ELineGauge::Measure ^{.NET Python} to fit the lines.

  • The method EShape::GetFound ^{.NET Python} returns TRUE if a suitable rectangle is found.

  • To obtain the EWedgeShape ^{.NET Python}, set the EShape::GetActualShape ^{.NET Python} property to TRUE to return the fitted line (instead of the nominal line position FALSE, default).

• Alternatively, EWedgeGauge::GetMeasuredWedge ^{.NET Python} provides the results as an EWedge ^{.NET Python} object.

Polygon Gauge

• A polygon is defined as a list of connected vertices, forming a closed or an open shape. EPolygonGauge ^{.NET Python} computes several transition points along each edge of the polygon, like with a line gauge. Then from these transition points, a measured polygon is computed with a strategy depending on the measurement mode.

In orange, the closed or open polygon gauge and, in green, the measured transition points

• The position of the vertices of the polygon are defined in the local EFrame ^{.NET Python} of the polygon.

  • An EFrame ^{.NET Python} is a coordinate system, with a position, an orientation and a scale.

  • The class EPolygon ^{.NET Python} stores the vertices and other attributes.

  • The class EPolygonShape ^{.NET Python} handles the hierarchy of the shapes and the drawing methods.

  • The class EPolygonGauge ^{.NET Python} is the main class for the measurement process.

Class dependency of the class EPolygonGauge

• To setup the polygon geometry, use the following methods:

  • EPolygon.SetCenter (derived from EPoint::SetCenter ^{.NET Python}), EPolygon.SetAngle (derived from EFrame::SetAngle ^{.NET Python}) and EPolygon.SetScale (derived from EFrame::SetScale ^{.NET Python}) to change the EFrame ^{.NET Python} reference coordinate system.

  • EPolygon::SetIsClosed ^{.NET Python} to choose between close or open polygon configuration.

  • EPolygon::AppendVertex ^{.NET Python} to add a new vertex to the polygon.

  • EPolygon::SetVertex ^{.NET Python} to change the position (x, y) of a vertex.

  • EPolygon::InsertVertex ^{.NET Python} to insert a vertex before the given index.

  • EPolygon::RemoveVertex ^{.NET Python} to remove a vertex at the given index.

  • EPolygonShape::AddVertexAtDisplayPosition ^{.NET Python} to insert a vertex depending on a display coordinate (typically a mouse click). This is useful for the graphical edition of a polygon.

  • EPolygonShape::RemoveVertexAtDisplayPosition ^{.NET Python} to remove the closest vertex to a display coordinate.

Note

EPolygonGauge ^{.NET Python} has 3 measurement modes EPolygonMeasurementMode ^{.NET Python}. The typical use cases are:

• For EPolygonMeasurementMode_Global ^{.NET Python}: the precise positioning of parts.

• For EPolygonMeasurementMode_Edge ^{.NET Python}: the verification of specific shapes defined by angles and lengths.

• For EPolygonMeasurementMode_Point ^{.NET Python}: the measure of complex object contours.

• Use the method EPolygonGauge::SetMeasurementMode ^{.NET Python} to select the measurement mode:

  • EPolygonMeasurementMode_Global ^{.NET Python}: The position, the orientation and optionally the scale of the polygon (EFrame ^{.NET Python}) are adjusted to fit the detected transition points.

Illustration of the Global measurement mode:
the measured polygon is a translation and a rotation of the input polygon

By default, the global transformation is rigid:

• Only the translation and the rotation are optimized to match the contour of the object.

• If scaling is required, you must explicitly enable it with the method EPolygonGauge::SetEnableScaling ^{.NET Python}.

• The global measurement doesn’t change the polygon vertex positions, it only adjusts the polygon frame.

  • EPolygonMeasurementMode_Edge ^{.NET Python}: Each polygon edge is measured individually.

    • A polygon composed by the union of these fitted edges is generated.

    • The number of edges of the measured polygon is the same as the input polygon.

The input polygon (blue) and the fitted polygon (green)

• EPolygonMeasurementMode_Point ^{.NET Python}: All transition points on the object contour are used to build a new polygon, with an optimized number of edges.

  • The resulting polygon is simplified using a filtering threshold to reduce the number of edges while keeping the shape of the object.

  • The resulting number of edges depends on the geometry of the contour of the object and on the filtering threshold.

  • Set the filtering threshold with EPolygonGauge::SetFilteringThreshold ^{.NET Python}.

A polygon gauge with a single edge produces a measured polygon that follows the contour of the object. Depending on the filtering threshold, the number of vertices is reduced.

• Other parameters of the class EPolygonGauge ^{.NET Python}.

  The class EPolygonGauge ^{.NET Python} inherits other common EasyGauge parameters:

  • EPolygonGauge::SetNumFilteringPasses ^{.NET Python} sets the number of filtering passes, then removes outliers before the line fitting operation. This parameter is only available in Global et Edge measurement modes.

  • EPolygonGauge::SetMinNumFitSamples ^{.NET Python} sets the minimum number of samples required for the fitting on each edge of the polygon. The measure fails if the minimum is not achieved.

  • EPolygonGauge::SetTransitionType ^{.NET Python} sets the transition type (ETransitionType ^{.NET Python}): white to black, black to white or both.

  • EPolygonGauge::SetTransitionChoice ^{.NET Python} selects which peak is used when there are several transitions.

  • EPolygonGauge::SetSamplingStep ^{.NET Python} gives the distance, in pixels, between two sample points.

Usage

• Sets the parameters of the gauge, then use EPolygonGauge::Measure ^{.NET Python} to fit the polygon.

  • The method EShape::GetFound ^{.NET Python} returns TRUE if a suitable polygon is found.

  • To obtain the polygon geometry, use the method EPolygonGauge::GetMeasuredPolygon ^{.NET Python}.