# 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)](learning.html.md)). - 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`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html) 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`](../../../doxygen_cpp/classeVision_1_1EPatternFinder.html#aa9de4e652c3d71bc83dda008fcf9ecc1) [_.NET](../../../doxygen_cs/classeVision_1_1EPatternFinder.html#aeee399ee9d9ba5e2d5e8b30094bd5bf3) [_Python](../../../doxygen_python/classeVision_1_1EPatternFinder.html#a4c2c47cfc0bd7de1d0a02b3f03414d59).  ### 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`](../../../doxygen_cpp/classeVision_1_1Legacy_1_1ELine.html) [_.NET](../../../doxygen_cs/classeVision_1_1Legacy_1_1ELine.html) [_Python](../../../doxygen_python/classeVision_1_1Legacy_1_1ELine.html), [`EPolygon`](../../../doxygen_cpp/classeVision_1_1Legacy_1_1EPolygon.html) [_.NET](../../../doxygen_cs/classeVision_1_1Legacy_1_1EPolygon.html) [_Python](../../../doxygen_python/classeVision_1_1Legacy_1_1EPolygon.html) and [`ECircle`](../../../doxygen_cpp/classeVision_1_1Legacy_1_1ECircle.html) [_.NET](../../../doxygen_cs/classeVision_1_1Legacy_1_1ECircle.html) [_Python](../../../doxygen_python/classeVision_1_1Legacy_1_1ECircle.html). * These shapes must be attached to [`EVectorModel::GetRoot()`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html#a5873c86a36af206330a3bc3a9fa644cf) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html#ae5ab8d320e29d426c7cd7852ab672d1a) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html#a915f7d164ba1c062474f77f3d358541b). * Each shape must potentially be [oriented](). #### SEE ALSO [Code snippet illustrating the usage of an `EPolygonShape` to define the `EVectorModel`](../../../resources/code_snippets/matching_and_measurement/easyfind/legacy/patternlearningandfindingwithshapeslegacy.html.md). ### 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`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html) from an external `dxf` file. Once loaded, the [`EVectorModel`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html): * 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](../../../resources/code_snippets/matching_and_measurement/easyfind/patternlearningandfindingwithdxf.html.md). ## Vector Model Parameters ### Scaling the Vector Model * Use the parameter [`EVectorModel::SetScale`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html#a4bb938306269e89a89735c66835e5866) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html#a07cc88a178687803920a6ca694a48935) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html#a775df1dca595bb9a4ad483c109913db1) 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`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html).  ### Centering the Vector Model * Use the parameter [`EVectorModel::SetCenter`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html#a2e63995af422e8fc2a96a39b27827e5d) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html#a0afb51d9b42589e1b66e42752817fb1d) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html#a6d091744233f27c30d06d906f9e977f9) to set or get the center of your vector model. - The center is the anchor point in the [`EVectorModel`](../../../doxygen_cpp/classeVision_1_1EVectorModel.html) [_.NET](../../../doxygen_cs/classeVision_1_1EVectorModel.html) [_Python](../../../doxygen_python/classeVision_1_1EVectorModel.html) coordinate system. - After the `Find`, you can retrieve its position in the search field coordinates as illustrated below.  ### 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`](../../../doxygen_cpp/classeVision_1_1Legacy_1_1EShape.html#a024d43df0f94b798ddc9c0ab58e0f4bd) [_.NET](../../../doxygen_cs/classeVision_1_1Legacy_1_1EShape.html#ad2be7d6d49abdd30ea4a6100d7729f04) [_Python](../../../doxygen_python/classeVision_1_1Legacy_1_1EShape.html#afc6b44a590701ba88fb7d1a97b8da8e7) method.  #### Code Sets the polarity of one of the `EShape` composing an `EVectorModel`. ### C++ ```c++ Legacy::EFrameShape& vectorModelRoot = vectorModel.GetRoot(); vectorModelRoot.GetDaughter(0)->SetProperty("polarity", "direct"); ``` ### C# ```c# Euresys.Open_eVision.Legacy.EFrameShape vectorModelRoot = vectorModel.Root; vectorModelRoot.GetDaughter(0).SetProperty("polarity", "direct"); ``` ### Python ```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.