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Header: AVL.h
Namespace: avl
Module: Barcodes

Extracts information from a barcode located on the input image at a given position.

Applications: Most often used after a barcode detection filter.


void avl::RecognizeBarcode
	const avl::Image& inImage,
	const avl::Rectangle2D& inBarcodePosition,
	atl::Optional<const avl::CoordinateSystem2D&> inBarcodePositionAlignment,
	atl::Optional<avl::BarcodeFormat::Type> inBarcodeFormat,
	const int inScanCount,
	const int inScanWidth,
	const float inMinStrength,
	const float inSmoothingStdDev,
	avl::Polarity::Type inPolarity,
	atl::Conditional<atl::String>& outDecodedText,
	atl::Conditional<avl::BarcodeFormat::Type>& outBarcodeFormat,
	atl::Optional<atl::Conditional<avl::Polarity::Type>&> outBarcodePolarity = atl::NIL,
	atl::Optional<avl::Rectangle2D&> outAlignedBarcodePosition = atl::NIL,
	atl::Array<avl::Segment2D>& diagScheduledScanSegments


Name Type Range Default Description
Input value
inImage const Image& Input image
Input value
inBarcodePosition const Rectangle2D& Position of the input image in which the barcode is located
Input value
inBarcodePositionAlignment Optional<const CoordinateSystem2D&> NIL Adjusts the barcode rectangle to the position of the inspected object
Input value
inBarcodeFormat Optional<BarcodeFormat::Type> EAN13 Format of the barcode
Input value
inScanCount const int 1 - 5 Number of parallel scans run until first successful read
Input value
inScanWidth const int 1 - 5 Width of the single scan
Input value
inMinStrength const float 0.0 - 5.0f Minimal strength of an extracted edge
Input value
inSmoothingStdDev const float 0.0 - 0.25f Standard deviation of the gaussian smoothing applied to the profile extracted in each scan
Input value
inPolarity Polarity::Type Dark Specifies whether code is darker or brighter than the background
Output value
outDecodedText Conditional<String>& Decoded barcode text or nothing if all of the scans failed
Output value
outBarcodeFormat Conditional<BarcodeFormat::Type>& Decoded barcode format or nothing if all of the scans failed
Output value
outBarcodePolarity Optional<Conditional<Polarity::Type>&> NIL Decoded barcode polarity or nothing if all of the scans failed
Output value
outAlignedBarcodePosition Optional<Rectangle2D&> NIL
Diagnostic input
diagScheduledScanSegments Array<Segment2D>& Scheduled scan segments

Optional Outputs

The computation of following outputs can be switched off by passing value atl::NIL to these parameters: outBarcodePolarity, outAlignedBarcodePosition.

Read more about Optional Outputs.


  • Connect inImage with the output of your image acquisition filter.
  • Select inBarcodeFormat according to the type of codes you want to read. If you choose the wrong format, the codes will not be recognized. Setting its value to Auto can increase the computation time considerably. Furthermore, the Auto value causes detection of UPC-A codes as EAN-13 codes.


Rotated barcode.

Low quality barcode printed on plastic foil.

Barcode on package wrapped in plastic foil.

Barcode on blurry image.

Barcode on standard 330ml can.

Barcode on reflective and wrapped surface.

EAN-13 with add-on 2 used to indicate a book edition.

EAN-13 with add-on 5 to give a suggestion for the price.


Minimal bar width requirement

To provide precise detection of the barcode width of the thinnest bar should be at least 1.5 pixels.

Depending on the barcode format guard or start/end code patterns must be readable.

Pharmacode usage

The pharmacode barcode type can be read correctly in both directions. To get results from both directions use a Pharmacode and PharmacodeInversed barcode types.

Before decoding a Pharmacode the code orientation angle is normalized to a range from -45° to 135° what makes the code decoding more stable

Results of reading using a different Pharmacode directions: Pharmacode = 23 and PharmacodeInversed = 16.

Using a relative coordinate systems

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

See Also

  • DecodeBarcode – Translates an array of bar widths to sequence of digits or text in accordance to the selected barcode standard.