decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 (Operator)

Name

decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 — Decode bar code symbols within a rectangle.

Signature

Description

The operator decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 uses the bar code model specified by BarCodeHandleBarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandle to decode a bar code at a given position within the image ImageImageImageImageimage. BarCodeHandleBarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandle must be created with create_bar_code_modelcreate_bar_code_modelcreate_bar_code_modelCreateBarCodeModelCreateBarCodeModel, its parameters can be set with set_bar_code_paramset_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParam. The position of the bar code is given as an arbitrarily oriented rectangle. Contrary to find_bar_codefind_bar_codefind_bar_codeFindBarCodeFindBarCode, where the decoding is preceeded by a time consuming search for candidate regions, decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 scans the provided region directly for bar codes. The rectangular region is defined by the parameters RowRowRowRowrow and ColumnColumnColumnColumncolumn for the center, PhiPhiPhiPhiphi for the orientation and Length1Length1Length1Length1length1 and Length2Length2Length2Length2length2 for the half edge lengths (see gen_rectangle2gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2). The angle PhiPhiPhiPhiphi also determines the reading direction and is defined as the angle between the reading direction of the bar code and the horizontal image axis. The angle is positive in counter clockwise direction and is given in radians as in gen_rectangle2gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2. Note that the angle unit deviates from the conventions in get_bar_code_resultget_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResult and set_bar_code_paramset_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParam where angles are given in degrees. PhiPhiPhiPhiphi can be in the range of ['-pi'"-pi""-pi""-pi""-pi"..'+pi'"+pi""+pi""+pi""+pi"]. The reading direction is perpendicular to the bars of the bar code. Bar codes with a reading direction PhiPhiPhiPhiphi + pi are also returned. Multiple regions for decoding can be given by supplying tuples for RowRowRowRowrow, ColumnColumnColumnColumncolumn, PhiPhiPhiPhiphi, Length1Length1Length1Length1length1 and Length2Length2Length2Length2length2.

The rectangle should cover completely the bar code and the quiet zones. Regions that are too big will be decoded, if there is no disturbing pattern within these regions and the height (Length2Length2Length2Length2length2) is small enough such that scanlines can be placed sufficiently dense. Rectangles that are too short in reading direction (Length1Length1Length1Length1length1) cannot be decoded.

decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 can be used if the position of the bar code is already known in advance. For example, the candidate regions found by find_bar_codefind_bar_codefind_bar_codeFindBarCodeFindBarCode and get_bar_code_objectget_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObject could be reused with a different code type (see the following example).

Multiple bar code types can be specified for CodeTypeCodeTypeCodeTypeCodeTypecodeType. See section Autodiscrimination for find_bar_codefind_bar_codefind_bar_codeFindBarCodeFindBarCode.

Further aspects of the actual decoding are explained with the operator find_bar_codefind_bar_codefind_bar_codeFindBarCodeFindBarCode.

Attention

A bar code model 'BarCodeHandle'"BarCodeHandle""BarCodeHandle""BarCodeHandle""BarCodeHandle" cannot be shared between two or more user's threads. Different bar code models can be used independently and safely in different threads.

Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Automatically parallelized on internal data level.

Parameters

Example (HDevelop)

read_image (Image, 'barcode/ean13/ean1301.png')
create_bar_code_model ([], [], BHandle)
find_bar_code (Image, SymReg, BHandle, '2/5 Industrial', Dec)
if (|Dec|=0)
*     A 2/5 Industrial code wasn't found. Try decoding an EAN-13 code.
    get_bar_code_object (CandReg, BHandle, 'all', 'candidate_regions')
    smallest_rectangle2 (CandReg, R, C, Phi, L1, L2)
    decode_bar_code_rectangle2 (Image, BHandle, 'EAN-13', R, C, Phi, \
                                L1, L2, Dec)
endif
clear_bar_code_model (BHandle)

Result

The operator decode_bar_code_rectangle2decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2 returns the value 2 (H_MSG_TRUE) if the given parameters are correct. Otherwise, an exception will be raised.

Possible Predecessors

create_bar_code_modelcreate_bar_code_modelcreate_bar_code_modelCreateBarCodeModelCreateBarCodeModel, set_bar_code_paramset_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParam, smallest_rectangle2smallest_rectangle2smallest_rectangle2SmallestRectangle2SmallestRectangle2

Possible Successors

get_bar_code_resultget_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResult, get_bar_code_objectget_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObject, clear_bar_code_modelclear_bar_code_modelclear_bar_code_modelClearBarCodeModelClearBarCodeModel

Alternatives

find_bar_codefind_bar_codefind_bar_codeFindBarCodeFindBarCode

See also

gen_rectangle2gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2

Module

Bar Code