Object Template Matcher

The class EObjectTemplateMatcher ^{.NET Python} is a tool designed to align and match the output of EasyObject to a reference template. It is designed to efficiently handle thousands of objects.

Workflow of the object template matcher.

Creating the Reference Template

Use the method BuildTemplate ^{.NET Python} to create the reference template, with one of the following parameters:

• An ECodedImage2 ^{.NET Python}, result of the method EImageEncoder::Encode ^{.NET Python}.

• An EObjectSelection ^{.NET Python}, a selection (subset) of ECodedImage2 ^{.NET Python} objects.

• A list of positions, given by a vector of points ^{.NET Python}.

An encoding of the reference image for use as the template.

The center positions of each object for use in the matching process.

Matching the objects

To perform object matching after setting up the template:

• Use the method Match ^{.NET Python} with an EObjectSelection ^{.NET Python} as parameter.

  • The bounding box center of the objects is the position used for the matching with the template.

• Or use the more generic method Match ^{.NET Python} with a std::vector<EPoint> as parameter.

Before matching, EObjectTemplateMatcher ^{.NET Python} performs an optional global rigid alignment of the submitted positions with the defined template.

The template.

The alignment of the submitted selection.

• An alignment consists of a translation and a rotation.

• Use the method SetAlignment ^{.NET Python} to enable one of the alignment processes.

• The available alignment processes are:

  • EObjectTemplateMatcherAlignment_Fast ^{.NET Python}: a fast and global alignment but that is not robust enough for all use cases.

  • EObjectTemplateMatcherAlignment_Local ^{.NET Python}: a local alignment that works well if the angle between the template and the selection is small and if there are not too many missing or extra objects.

  • EObjectTemplateMatcherAlignment_Robust ^{.NET Python}: a slower but more robust algorithm.

Tip

For EObjectTemplateMatcherAlignment_Fast ^{.NET Python} and EObjectTemplateMatcherAlignment_Robust ^{.NET Python}, you can also specify a maximum angle with the method SetMaximumAngle ^{.NET Python}. This is especially useful when the objects form a (nearly) symmetric pattern.

After the optional alignment, EObjectTemplateMatcher ^{.NET Python} matches the submitted positions with the reference template.

• It uses the shortest distance criterion to pair these positions with the template.

• You can set the maximum distance to constraint the search. This can speed up processing.

Retrieving the Matching Results

• Use one of these methods to retrieve the matching results:

  • GetSelectionIndexes ^{.NET Python} returns, for each position in the template, the paired index in the selection. The value -1 is used if the object in the template has no correspondence in the selection. Alternatively, use the method GetMatched ^{.NET Python} to retrieve the corresponding objects or points.

  • GetTemplateIndexes ^{.NET Python} returns, for each position in the selection, the paired index in the template. The value -1 is used if the object in the selection has no correspondence in the template. Alternatively, use the method GetMatched ^{.NET Python} (with the argument fromSelection set to false) to retrieve the corresponding objects or points.

  • GetUnpairedObjects ^{.NET Python} returns the positions in the template and in the selection that have not been paired. Alternatively, use the methods GetMissing ^{.NET Python} and EObjectTemplateMatcher::GetExtra ^{.NET Python} to retrieve the corresponding objects or points.

• Use the method GetNumberOfPairedObjects ^{.NET Python} to get the total number of paired objects.

• Use the methods Save ^{.NET Python} and Load ^{.NET Python} to store and retrieve the configuration of an EObjectTemplateMatcher ^{.NET Python} object, including the template.

Matching results.