F_VN_GradeBarcodeExp

Syntax

Definition:

FUNCTION F_VN_GradeBarcodeExp : HRESULT
VAR_INPUT
    ipSrcImage            : ITcVnImage;
    ipDecodedData         : Reference To  ITcVnContainer;
END_VAR
VAR_IN_OUT
    stCodeGrades          : TcVnCodeGrades1D;
END_VAR
VAR_INPUT
    eBarcodeType          : ETcVnBarcodeType;
    eSearchDirection      : ETcVnBarcodeSearchDirection;
    ipResultVisualization : Reference To  ITcVnImage;
    ipScanLineInfo        : Reference To  ITcVnContainer;
    ipContour             : Reference To  ITcVnContainer;
    hrPrev                : HRESULT;
END_VAR
VAR_OUTPUT
    fAngleDeg             : REAL;
END_VAR

 Inputs

 In/Outputs

 Outputs

 Return value

HRESULT

Further information

The function F_VN_GradeBarcodeExp is an expert variant of F_VN_GradeBarcode. It contains additional parameters.

Parameter

Input image

The input image ipSrcImage must be an 1-channel image with element type USINT (8 bits). The input image may only contain the code to be checked, including the corresponding quiet zones. The barcode must be aligned horizontally or vertically and must not have any text or blank space more than 10% of the total height above or below it. The quiet zones are located to the left and right of the code when aligned horizontally.

To achieve meaningful results, uniform illumination, not underexposed or overexposed, good focusing on the code plane and an image sensor plane aligned parallel to it are required. Furthermore, the image resolution must be high enough to match the line width. For barcodes, the minimum bar width should be covered by at least 3 pixels in order to achieve good results.

Read data

The data read from the code are returned as a string in the container ipDecodedData. The container is of the type ContainerType_String_SINT. Once the code has been successfully found and decoded, the content can be exported to a string using the function F_VN_ExportContainer_String.

hr := F_VN_ExportSubContainer_String(ipDecodedData, sText, nMaxLength, hr);

Different decoding results Decoding with the respective reference algorithm can lead to deviating results. It is therefore possible that the code content can be read by other devices or functions, but the reference algorithm fails.

Return of the quality assessment

The return value stCodeGrades of type TcVnCodeGrades1D contains the determined individual results and an overall total result fOverall. The quality grades ranges from 0 (very poor) to 4 (very good). The results are averaged over several scan lines.

Parameter	Description
fDecode	Evaluates whether the code could be decoded with the reference algorithm.
fSymbolContrast	Evaluates the global symbol contrast, i.e. the difference between the brightest and darkest value on the entire scan line.
fMinReflectance	Evaluates the ratio of the darkest to the brightest value of the scan lines.
fMinEdgeContrast	Evaluates the minimum local contrast of neighboring elements of the scan lines.
fModulation	Evaluates the ratio between the minimum local contrast and the global symbol contrast.
fDefects	Evaluates irregularities within elements and quiet zones.
fDecodability	Evaluates how reliably the code can be decoded with the reference algorithm.
fOverall	The overall score of the code is the lowest score achieved in the individual tests, averaged over all scan lines. If different scan lines lead to different decoded data, the overall score is 0.

Barcode type

The parameter eBarcodeType defines the barcode type whose print quality is to be assessed. The following barcode types from the enum ETcVnBarcodeType are supported:

• TCVN_BT_CODE39
• TCVN_BT_CODE128
• TCVN_BT_EAN8
• TCVN_BT_EAN13
• TCVN_BT_ITF
• TCVN_BT_UPCA
• TCVN_BT_UPCE

Search direction

The search direction can be specified via eSearchDirection:

• With TCVN_BSD_ANY, the search is first carried out in the horizontal direction and then in the vertical direction.
• With TCVN_BSD_HORIZONTAL, the search is only carried out in a horizontal direction.
• With TCVN_BSD_VERTICAL, the search is only carried out in the vertical direction.

Presentation of results

ipResultVisualization returns an image with the visualization of the scan lines and the respective evaluation results. The lines are color-coded according to the individual grades: >= 3 as green, >= 2 as light blue, >= 1 as orange, < 1 as red. This parameter is optional and can be set to 0 if it is not required.

Scan line information

ipScanLineInfo returns additional information about the individual scan lines for a more detailed evaluation. The return values are of the type ContainerType_Vector_TcVnVector3_REAL and specify the index of the image row or image column, the total score and the global threshold determined for each scan line, depending on the orientation. The individual lines can be visualized with F_VN_PlotIntensityProfile, for example. This parameter is optional and can be set to 0 if it is not required.

Position of the code

The parameter ipContour returns the code corner points, including the quiet zone, as four contour points of the type ContainerType_Vector_TcVnPoint2_DINT. The calculation is based only on the scan lines that could be decoded. The contour can be drawn directly with F_VN_DrawContours, for example, or further analyzed with the Contour Analysis functions. This parameter is optional and can be set to 0 if it is not required.

Rotation angle ^{(return value)}

fAngleDeg returns the clockwise rotation angle in 90° steps.

Application

The print quality of a barcode can be determined in this way, for example:

hr := F_VN_GradeBarcodeExp(
    ipSrcImage            := ipSrcImage,
    ipDecodedData         := ipDecodedData,
    stCodeGrades          := stCodeGrades,
    eBarcodeType          := eBarcodeType,
    eSearchDirection      := eSearchDirection,
    ipResultVisualization := ipResultVisualization,
    ipScanLineInfo        := ipScanLineInfo,
    ipContour             := ipContour,
    hrPrev                := hr,
    fAngleDeg             => fAngleDeg);

Required License

TC3 Vision Code Quality

System Requirements