Learn a Pattern from Vectors

Learning

EasyFind detects the instances of a pattern in images.

• The reference pattern is a set of all the feature points that EasyFind computes during the learning process:

  • EasyFind can extract these points from a bitmap representation of the pattern (see Learn the Pattern from Image(s)).

  • Or it can use the feature points that are directly given by geometrical shapes as described below.

• To learn a pattern from geometrical shapes:

  • Use the class EVectorModel ^{.NET Python} to hold a collection of shapes as a vector model.

  • Load the EVectorModel from an external dxf file or use the eVision API to define it.

  • that EVectorModel object is then input to EPatternFinder::Learn ^{.NET Python}.

A geometrical shape model and its corresponding features

Learn a set of EShape

Note

Creating an EVectorModel from a set of EShape is not available in eVision Studio, but loading a dxf file is.

• To define the geometrical shapes of your model, you can directly define ELine ^{.NET Python}, EPolygon ^{.NET Python} and ECircle ^{.NET Python}.

• These shapes must be attached to EVectorModel::GetRoot() ^{.NET Python}.

• Each shape must potentially be oriented.

See also

Code snippet illustrating the usage of an EPolygonShape to define the EVectorModel.

Learn a dxf file

Note

This feature is available in eVision Studio.

Alternatively, to define the geometrical shapes of your model, you can load an EVectorModel ^{.NET Python} from an external dxf file.

Once loaded, the EVectorModel ^{.NET Python}:

• Holds a collection of shapes.

• Holds a center position depending on the method used for the definition of the dxf.

• Each shape must potentially still be oriented.

See also

Code snippet illustrating the creation of a EVectorModel from a dxf file.

Vector Model Parameters

Scaling the Vector Model

• Use the parameter EVectorModel::SetScale ^{.NET Python} to set the scale of your vector model.

  • The scale represents the size of the instances in the search field (in pixels) divided by their size in the EVectorModel ^{.NET Python}.

A vector model with a scale of 10 and the corresponding instance

Centering the Vector Model

• Use the parameter EVectorModel::SetCenter ^{.NET Python} to set or get the center of your vector model.

  • The center is the anchor point in the EVectorModel ^{.NET Python} coordinate system.

  • After the Find, you can retrieve its position in the search field coordinates as illustrated below.

A vector model whose center is on its left and the corresponding instance

Orienting the Transitions in the Vector Model

• To search for light to dark or dark to light transitions, set the polarity attribute for the vector model with the EShape::SetProperty ^{.NET Python} method.

The same vector model with 2 different orientation and the corresponding instances

Code

Sets the polarity of one of the EShape composing an EVectorModel.

C++

Legacy::EFrameShape& vectorModelRoot = vectorModel.GetRoot();
vectorModelRoot.GetDaughter(0)->SetProperty("polarity", "direct");

C#

Euresys.Open_eVision.Legacy.EFrameShape vectorModelRoot = vectorModel.Root;
vectorModelRoot.GetDaughter(0).SetProperty("polarity", "direct");

Python

vectorModelRoot = vectorModel.Root
vectorModelRoot.GetDaughter(0).SetProperty("polarity", "direct")

Note

We recommend tuning this graphically in eVision Studio rather than through the API. You can have a look at the sample “Find a vector pattern” specifically.