F_VN_OCRExp

Syntax

Definition:

FUNCTION F_VN_OCRExp : HRESULT
VAR_INPUT
    ipSrcImage      : ITcVnImage;
    eModel          : ULINT;
    ipCharacters    : Reference To  ITcVnContainer;
    sPattern        : STRING;
    eOcrOptions     : UDINT;
    ipBoundingBoxes : Reference To  ITcVnContainer;
    ipConfidences   : Reference To  ITcVnContainer;
    hrPrev          : HRESULT;
END_VAR
VAR_OUTPUT
    fMinConfidence  : REAL;
END_VAR

 Inputs

 Outputs

 Return value

HRESULT

Further information

The function F_VN_OCRExp is the expert variant of F_VN_OCR. It contains additional parameters.

Parameter

Input image

The input image that is transferred to ipSrcImage must be a 1-channel binary image. Only white characters on a black background are permitted.

Model

The model types of ETcVnOcrModelType that are to be used to classify the characters in a function call must be transferred to eModel. To be able to use several models with one function call, a string pattern must be specified via sPattern. The models can be linked with a OR.

To be able to use the individual models, they must first be initialized with the function block FB_VN_InitializeFunction.

Recognized characters

The recognized characters are returned via the reference ipCharacters.

String pattern

A string pattern with the expected format of the character string to be recognized can be transferred via sPattern.

Supported formatting and its meaning:

• ! (exclamation mark) to ignore characters (does not apply to spaces)
• . (point) for any character (does not apply to spaces)
  The use of the point is only supported with the TCVN_OMT_NUMBERS_SC_UCLETTERS model, otherwise the point has the same effect as an exclamation mark and an S_FALSE is output.
• _ (underscore) for a space (independent of eOcrOptions)
• d (number) for an expected number of 0-9
• # (special character) for an expected special character, supported are . / - : =
• u (capital letter) for an expected capital letter of A-Z

Options

With eOcrOptions, options (ETcVnOcrOptions) can be specified that influence the functionality and result output. If no options are required, a 0 must be passed.

Bounding Boxes

The reference ipBoundingBoxes can optionally be used to return the corresponding bounding boxes of the recognized characters. If no bounding boxes are required, the value 0 can be transferred.

Confidences

The reference ipConfidences can optionally be used to return the corresponding classification confidences of the recognized characters. If no confidences are required, the value 0 can be transferred.

Minimum confidence

The optional return value fMinConfidence returns the minimum confidence value of all characters found.

Application

For example, a call to the OCRExp function, with two models for recognizing numbers and capital letters, with subsequent string export looks like this:

sPattern := 'dd!uuu!dddd'; // e.g. 02-FEB-2024

hr := F_VN_OCRExp(
    ipSrcImage      := ipBinaryImage,
    eModel          := TCVN_OMT_NUMBERS OR TCVN_OMT_UCLETTERS,
    ipCharacters    := ipCharactersResults,
    sPattern        := sPattern,
    eOcrOptions     := eOcrOptions,
    ipBoundingBoxes := ipBoundingBoxes,
    ipConfidences   := ipConfidences,
    hrPrev          := hr,
    fMinConfidence  => fMinConfidence);

// Export character to string
hr := F_VN_ExportSubContainer_String(ipCharactersResults, 0, sText, 255, hr);

// Get the bounding box of the first element
hr := F_VN_GetAt_TcVnRectangle_DINT(ipBoundingBoxes, stRectangle, 0, hr); 

// Get the Confidence value of the first element
hr := F_VN_GetAt_REAL(ipConfidences, fConfidence, 0, hr);

To evaluate the confidence values or to draw bounding boxes, individual elements of the containers can be accessed via GetAt. However, if you want to access several or all elements of a container, it is advisable to program a loop or export the ipConfidences container completely as an array.

Required License

TC3 Vision OCR

System Requirements