F_VN_OCR

Detects and recognizes characters in a binary image (white characters on black background).
Can use available TwinCAT Job Tasks for executing parallel code regions.

Syntax

Definition:

FUNCTION F_VN_OCR : HRESULT
VAR_INPUT
    ipSrcImage   : ITcVnImage;
    eModel       : ULINT;
    ipCharacters : Reference To  ITcVnContainer;
    hrPrev       : HRESULT;
END_VAR

Inputs

Name	Type	Description
ipSrcImage	ITcVnImage	Source image (USINT elements, 1 or 3 channels). The required number of channels depends on the selected model type.
eModel	ULINT	Selection of OCR model types (ETcVnOcrModelType)
ipCharacters	Reference To ITcVnContainer	Returns the recognized characters (ContainerType_Vector_String_SINT)
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

Return value

HRESULT

Further information

The function F_VN_OCR detects and recognizes characters in a binary image and returns the recognized characters in a container.

Parameter

Input image

The format of the input image that must be provided to ipSrcImage depends on the model used:

For models whose names begin with TCVN_OMT_, you must provide a 1-channel binary image that permits only white characters on a black background.
For the model that begins with TCVN_OMT_CNN_, a 1-channel or 3-channel image of type USINT (8 bits) must be passed, which is automatically converted internally. The specific input format and size of the model are listed in the description of ETcVnOcrModelType. In order to reduce the internal conversion steps and thus also the computing time required, it is recommended to transfer the image with the same number of channels if it already exists in the form before the call. In general, it should be ensured that the aspect ratio of the input image is as similar as possible to that of the model. Otherwise, the internal scaling may result in distortions that impair the detection quality.

Model

A model type of ETcVnOcrModelType, which is to be used in a function call to classify the characters, must be transferred to eModel. This function only supports the use of one model per function call.

To be able to use a model, it must first be initialized with the function block FB_VN_InitializeFunction.

Recognized characters

The recognized characters are returned via the reference ipCharacters.

Expert parameters

The expert variant F_VN_OCRExp contains additional parameters.

Application

For example, a call of the OCR function, with a model for recognizing numbers, with subsequent string export looks like this:

hr := F_VN_OCR(
    ipSrcImage   := ipBinaryImage,
    eModel       := TCVN_OMT_NUMBERS,
    ipCharacters := ipCharactersResults,
    hrPrev       := hr);

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

Examples:

OCR

Required License

TC3 Vision OCR

System Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT V3.1.4024.59 or later	PC or CX (x64) with min. PL50, e.g. Intel 4-core Atom CPU	Tc3_Vision