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ReadMultipleQRCodes

Header:	FIL.h
Namespace:	fil
Module:	Datacodes

Detects and recognizes all QR codes on the input image.

Syntax

void fil::ReadMultipleQRCodes
(
	const fil::Image& inImage,
	ftl::Optional<const fil::Rectangle2D&> inRoi,
	ftl::Optional<const fil::CoordinateSystem2D&> inRoiAlignment,
	int inMaxCodeCount,
	float inMinModuleSize,
	float inMaxModuleSize,
	ftl::Optional<float> inContrastThreshold,
	ftl::Optional<int> inPatternQuality,
	bool inAllowRotation,
	fil::Polarity::Type inPolarity,
	ftl::Optional<float> inMinLineMagnitude,
	ftl::Array<fil::QRCode>& outQRCodes,
	ftl::Optional<fil::Rectangle2D&> outAlignedRoi = ftl::NIL
)

Parameters

Name	Type	Range	Default	Description
inImage	const Image&			Input image
inRoi	Optional<const Rectangle2D&>		NIL	Range of pixels to be processed
inRoiAlignment	Optional<const CoordinateSystem2D&>		NIL	Adjusts the region of interest to the position of the inspected object
inMaxCodeCount	int	1 - 255	2	Maximum number of codes in one image
inMinModuleSize	float	1.5 - 100.0	4.0f	Lower estimated size of a code unit in pixels
inMaxModuleSize	float	1.5 - 100.0	40.0f	Upper estimated size of a code unit in pixels
inContrastThreshold	Optional<float>	1.0 - 255.0	NIL	Guaranteed gray level difference between dark and bright modules
inPatternQuality	Optional<int>	1 - 3	NIL	Quality of the code from 1 (extremely deformed) to 3 (perfect)
inAllowRotation	bool		True	Allows codes rotated in relation to the axes of the input image
inPolarity	Polarity::Type		Any	Specifies whether code is darker or brighter than the background
inMinLineMagnitude	Optional<float>	1.0 - 255.0	NIL	Strength of an edge within the code; default depends on parameters
outQRCodes	Array<QRCode>&
outAlignedRoi	Optional<Rectangle2D&>		NIL	Input ROI after transformation (in the image coordinates)

Optional Outputs

The computation of following outputs can be switched off by passing value ftl::NIL to these parameters: outAlignedRoi.

Description

The filter locates and decodes QR code on the image (inImage) within given region (inRoi). The encoded text length must be greater than 2.

inMinModuleSize is the expected lower bound of one module (smallest unit of the code). If there are multiple codes, size of the smallest one should be provided.

inMinModuleSize is the expected upper bound of one module (smallest unit of the code). If there are multiple codes, size of the smallest one should be provided.

Parameter inMaxCodeCount determines how many codes are to be found within the image. Thus the algorithm continues searching until it reaches the desired number of codes or has nowhere to search. Too high value can significantly extend the filter execution time.

Parameter inContrastThreshold describes contrast of the code - namely, it denotes the brightness difference between light and dark modules of the code. If not given, the algorithm uses normalization of the image to enhance the code and computes this value automatically.

inPatternQuality is an integer from the range <1,3> describing how much the code is blurred or the positional patterns are deformed. For instance, value 3 corresponds to a perfect quality code, while value 1 to an extremely blurred one. For standard cases it is recommended to use quality of 2 or to leave it default.

inAllowRotation Allows codes rotated in relation to the axes of the input image.

inPolarity Setup polarity of QR code can improve performance of ReadingQRCodes

inMinLineMagnitude describes strength of an edge within the code. This value determined automatically is usually correct, so this parameter can be viewed as a hint for the algorithm in nonstandard, tough cases.

Examples

Simple case.

Dark and lower quality code.

Multiple codes within one image.

Code viewed from an angle.

Remarks

To be correctly detected, the code should have safety area around it (of same brightness as the code background color) at least as wide as its unit. Moreover, unit size should be at least 2 pixels.