Bubbles

• An OMR bubble is defined in this document as a circle, oval, square, or rectangle used on business forms to delineate areas that are to be hand filled or marked to indicate a choice. A bubble can be completely or partially filled in, or can be simply marked with a check-mark, ‘X’, or some other mark. For the default OMR behavior (RecognitionEngine = SingleThreshold),  set the property Threshold to a value representing the mark density required for a mark bubble.  For legacy OMR behavior (RecognitionEngine = DualThresholdLegacy), set the property MarkedBubbleThreshold to a value representing the mark density required for a mark bubble.   Choose a value according to the type of mark expected; the threshold value should be lower for bubbles which are simply checked instead of actually filled in completely.
• If you are using legacy OMR behavior (RecognitionEngine = DualThresholdLegacy),  set the property MarkedBubbleThreshold to a value representing the mark density required for a mark bubble.
• Use the OmrBubbleModel to define a bubble model or template and pass in the Value of a character or string which contains the text to return if the bubble is determined to be marked.
• The OmrBubbleModelCollection which contains many OmrBubbleModel objects can then be used in the OmrSegmentModel object for further OMR analysis.
• The OmrBubbleResult will give the result of the OMR bubble analysis. Several properties are set, providing detailed information on the findings:
  • The MarkDensity property indicates the density of the mark in the bubble.
  • The Value property indicates the value that this bubble result corresponds to (see OmrBubbleModel.Value).
  • The MarkState property indicates if the bubble was marked or unmarked.

Segments

• An OMR segment is defined as a rectangle containing a specified number of columns and rows of bubbles to be evaluated.
• Use the OmrSegmentModel to define a segment model or template and define the Bubbles to be analyzed.
• The shape of the bubbles within the segment is specified by the BubbleShape property and used to compute the discrete areas of the bubbles. Within the bubbles, dark pixels are counted and compared against the bubble areas to determine which bubbles qualify as filled in. The Threshold value can be set using the Threshold property to specify the percentage of fill required to constitute a filled-in bubble. The pixels that make up the bubbles themselves are counted in this process when OMRProcessor.AnalysisComparisonMethod  property is set to "None."
  

  When the RecognitionEngine is set to DualThresholdLegacy, the fill percentage threshold is set using the MarkedBubbleThreshold property.

• The appropriate text and confidence score is returned in the results for the filled-in bubbles.

Signature Detection

• Signature detection is provided by selecting the area around the signature and creating a single bubble field to detect it.
• This type of analysis is supported through the use of the OmrBubbleModel objects.

Fields

• A field contains the OmrSegmentModelCollection with their bubble analysis data.
• Define a field through the properties and methods in the OmrProcessor object.
• Field results including the Confidence, Segments, and Text are obtained within the OmrFieldResult object.

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