decode_bar_code_rectangle2T_decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 (Operator)

Name

decode_bar_code_rectangle2T_decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 — Decode bar code symbols within a rectangle.

Signature

Description

The operator decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 uses the bar code model specified by BarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandlebar_code_handle to decode a bar code at a given position within the image ImageImageImageimageimage. BarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandlebar_code_handle must be created with create_bar_code_modelcreate_bar_code_modelCreateBarCodeModelCreateBarCodeModelcreate_bar_code_model, its parameters can be set with set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamset_bar_code_param. The position of the bar code is given as an arbitrarily oriented rectangle. Contrary to find_bar_codefind_bar_codeFindBarCodeFindBarCodefind_bar_code, where the decoding is preceded by a time consuming search for candidate regions, decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 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 Length1Length1Length1length1length_1 and Length2Length2Length2length2length_2 for the half edge lengths (see gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2gen_rectangle2). 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_rectangle2GenRectangle2GenRectangle2gen_rectangle2. Note that the angle unit deviates from the conventions in get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultget_bar_code_result and set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamset_bar_code_param where angles are given in degrees. PhiPhiPhiphiphi can be in the range of []. The reading direction is perpendicular to the bars of the bar code. Bar codes with a reading direction are also returned. Multiple regions for decoding can be given by supplying tuples for RowRowRowrowrow, ColumnColumnColumncolumncolumn, PhiPhiPhiphiphi, Length1Length1Length1length1length_1 and Length2Length2Length2length2length_2.

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 (Length2Length2Length2length2length_2) is small enough such that scanlines can be placed sufficiently dense. Rectangles that are too short in reading direction (Length1Length1Length1length1length_1) cannot be decoded.

decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 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_codeFindBarCodeFindBarCodefind_bar_code and get_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObjectget_bar_code_object could be reused with a different code type (see the following example).

Multiple bar code types can be specified for CodeTypeCodeTypeCodeTypecodeTypecode_type. See section Autodiscrimination for find_bar_codefind_bar_codeFindBarCodeFindBarCodefind_bar_code.

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

Execution Information

• 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.

This operator supports canceling timeouts and interrupts.

This operator modifies the state of the following input parameter:

• BarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandlebar_code_handle

During execution of this operator, access to the value of this parameter must be synchronized if it is used across multiple threads.

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

Result

The operator decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2 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_modelCreateBarCodeModelCreateBarCodeModelcreate_bar_code_model, set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamset_bar_code_param, smallest_rectangle2smallest_rectangle2SmallestRectangle2SmallestRectangle2smallest_rectangle2

Possible Successors

get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultget_bar_code_result, get_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObjectget_bar_code_object, clear_bar_code_modelclear_bar_code_modelClearBarCodeModelClearBarCodeModelclear_bar_code_model

Alternatives

find_bar_codefind_bar_codeFindBarCodeFindBarCodefind_bar_code

See also

gen_rectangle2gen_rectangle2GenRectangle2GenRectangle2gen_rectangle2

Module

Bar Code