2D Alignment

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Description

This Step is used to align the input image to a template via translation, rotation, and scaling, ensuring the consistency between the two.

Usage Scenario

This Step is a general image processing Step.

Workflow

The process of configuring this Step is shown below:

  1. Configure the input. Connect the ports manually or select the input(s) under Input in the parameter configuration panel.

  2. Make and select a template. For more information on how to make a template, please refer to 2D Template Editor.

  3. Set Matching Parameters.

  4. Select the desired output items under Output.

  5. Run the Step and view output.

Parameter Description

Parameter Description

ROI Settings

The ROI is used to define the image area to be processed by the algorithm. Once this parameter is selected, the Step will only use the data in the ROI to match the template.

See 2D ROI Settings to learn how to set and adjust the ROI.

Mask Settings

For template matching, the system ignores the image regions covered by the masks. For the mask settings and adjustment methods, refer to ROI Settings.

Template Settings

Parameter Description

Select Template

This parameter is used to specify the matching template.

Click Open the editor to open 2D Template Editor, where you can edit the template for alignment. After specifying and saving the template, click ▼ and select the template in the drop-down menu. For instructions on how to use the editor, see 2D Template Editor.

Matching Settings

Frequently Used Parameters

Parameter Description

Edge Polarity Sensitive

This parameter controls whether edge polarity must match the template. The polarity indicates the direction of intensity changes along the edges, e.g., light-to-dark or dark-to-light.

If there is not a large disparity in the data acquisition scenarios, enable this option to ensure matching accuracy. If there is a large disparity, disable this option to enhance the matching generalization ability.

Enabled by default.

Min Matching Score

This parameter is used to determine whether a matching result is valid. Any result whose score is below this value will be discarded.

Default value: 50.0

Min Scale Ratio

The minimum scale ratio of the target relative to the template. A narrower scale ratio range improves matching speed.

Default value: 1.00

Max Scale Ratio

The maximum scale ratio of the target relative to the template. A narrower scale ratio range improves matching speed.

Default value: 1.00

Min Rotation Angle

The minimum rotation angle of the target relative to the template. A narrower rotation angle range improves matching speed.

Default value: -15°

Max Rotation Angle

The maximum rotation angle of the target relative to the template. A narrower rotation angle range improves matching speed.

Default value: 15°

  • Min Scale Ratio must be less than or equal to Max Scale Ratio.

  • Min Rotation Angle must be less than or equal to Max Rotation Angle.

Advanced Parameters

Parameter Description

Min Valid Match Ratio

The minimum ratio of valid matched edge points to the total number of edge points in the template.

Default value: 50%

Search Radius

The radius of the circular search area for finding corresponding matching points of each template feature point in the target image during pose refinement.

Default value: 8

When the matching result is not good, increase the value appropriately.

Max Overlap Ratio

Used to filter out duplicate matching results. If there is an overlap between two matching results and the overlap ratio exceeds this value, only the result with the higher matching score will be retained.

Default value: 50%

Padding Ratio

Specifies the ratio of allowed padded size to template size when the target object may be partially outside the image. Padding can recover edge matches that would otherwise fail, but generally increases computation.

When a part of the object to be matched is outside the image, this parameter must be set. If the proportion of the template outside the image after matching exceeds this value, the match is considered unsuccessful.

After upgrading a project created in an earlier version, if no matching result is obtained, increase Padding Ratio as appropriate or adjust the ROI so that it fully covers the object to be matched.

Edge Threshold Type

How the edge threshold is set.

  • Template threshold: use the edge threshold saved in the template.

  • Custom threshold: use the edge threshold set by the user.

In most cases, use Template threshold. If the input image differs significantly from the image used to create the template, enable Show Edge Points to check the edge extraction result. If the result is unsatisfactory, set Edge Threshold Type to Custom threshold and adjust Edge Threshold.

Edge Threshold

Points with gradient magnitude greater than or equal to this value are considered edge features for template matching.

This parameter is visible only when Edge Threshold Type is set to Custom threshold.

Show Edge Points

When enabled, the data visualization window displays the extracted edge points.

This parameter is for visualization only and does not affect the processing result.

Output Description

Select the output item(s) to add the output port(s) to the Step, and the corresponding data will be output after the Step is run. You can select the output according to the actual measurement requirements.

If you select an expandable output item, you must expand it by clicking ▶, and then set the Lower Limit and Upper Limit values to determine the acceptable range. If the output value falls within the acceptable range, the measurement item is judged as OK; otherwise, it is judged as NG.
Output Item Description

Aligned Image

The image after alignment.

Matching Score

Used to evaluate the match quality.

Alignment Parameter Group

Provides the translation, rotation, and scale parameters required to align the matched object with the template.

See Alignment Parameter Group to learn about its usage scenarios.

Object Pose

The position, orientation, and scale of the object in the image after alignment.

Object Bounding Box

Bounding box of the matched object, derived from the template bounding box based on the matching result.

Troubleshooting

See Error Code List for common error messages and solutions.

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