find_bar_codeT_find_bar_codeFindBarCodeFindBarCodefind_bar_code (Operator)

Name

find_bar_codeT_find_bar_codeFindBarCodeFindBarCodefind_bar_code — Detect and read bar code symbols in an image.

Signature

Description

The operator find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code finds and reads bar code symbols in a given image (ImageImageImageImageimageimage) and returns the decoded data. In one image an arbitrary number of bar codes of a single type can be read. The type of the desired bar code symbology is given by CodeTypeCodeTypeCodeTypeCodeTypecodeTypecode_type. The decoded strings are returned in DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStringsdecoded_data_strings and the corresponding bar code regions in SymbolRegionsSymbolRegionsSymbolRegionsSymbolRegionssymbolRegionssymbol_regions. For a total of n successfully read bar codes, the indices from 0 to (n-1) can be used as candidate handle in the operators get_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObjectGetBarCodeObjectget_bar_code_object and get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultGetBarCodeResultget_bar_code_result in order to retrieve the desired data of one specific bar code result.

Bar codes are expected to appear dark on a light background. To read light bar codes on a dark background, invert the input image using the operator invert_imageinvert_imageInvertImageInvertImageInvertImageinvert_image beforehand.

Before calling find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code a bar code model must be created by calling create_bar_code_modelcreate_bar_code_modelCreateBarCodeModelCreateBarCodeModelCreateBarCodeModelcreate_bar_code_model. This operator returns a bar code model BarCodeHandleBarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandlebar_code_handle, which is input to find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code.

The output value DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStringsdecoded_data_strings contains the decoded string of the symbol for each bar code result. The contents of the strings are conform to the appropriate standard of the symbology. Typically, DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStringsdecoded_data_strings contains only data characters. For bar codes with a mandatory check character the check character is not included in the string. For bar codes with an optional check character, like for example Code 39, Codabar, 2/5 Industrial or 2/5 Interleaved, the result depends on the value of the 'check_char'"check_char""check_char""check_char""check_char""check_char" parameter, which can be set in create_bar_code_modelcreate_bar_code_modelCreateBarCodeModelCreateBarCodeModelCreateBarCodeModelcreate_bar_code_model, set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param or set_bar_code_param_specificset_bar_code_param_specificSetBarCodeParamSpecificSetBarCodeParamSpecificSetBarCodeParamSpecificset_bar_code_param_specific: The default setting of 'absent'"absent""absent""absent""absent""absent" assumes that no check character is present. In this case, no check is performed and all characters are returned as data. When set to 'present'"present""present""present""present""present", a check character is expected and used to verify the correctness of the bar code. The bar code is graded as unreadable if the check sum does not match. Accordingly, the symbol region and the decoded string do not appear in the list of resulting strings (DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStringsdecoded_data_strings) and in the list of resulting regions (SymbolRegionsSymbolRegionsSymbolRegionsSymbolRegionssymbolRegionssymbol_regions). The check character itself is stripped from the data. If this stripping is undesired, the mode 'preserved'"preserved""preserved""preserved""preserved""preserved" allows to verify the bar code while still keeping the check character in the data.

The underlying decoded reference data, including start/stop and check characters, can be queried by using the get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultGetBarCodeResultget_bar_code_result operator with the option 'decoded_reference'"decoded_reference""decoded_reference""decoded_reference""decoded_reference""decoded_reference".

Following bar code symbologies are supported:

Note that the PharmaCode can be read in forward and backward direction, both yielding a valid result. Therefore, both strings are returned and concatenated into a single string in DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStringsdecoded_data_strings by a separating comma.

Note that the GS1 DataBar bar codes may contain an additional composite code component. To find and decode this component, set the parameter 'composite_code'"composite_code""composite_code""composite_code""composite_code""composite_code" to 'CC-A/B'"CC-A/B""CC-A/B""CC-A/B""CC-A/B""CC-A/B" using the operator set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param.

Note that also a bar code of type 'Code 32' can be read by using find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code with CodeTypeCodeTypeCodeTypeCodeTypecodeTypecode_type set to 'Code 39'"Code 39""Code 39""Code 39""Code 39""Code 39" in combination with the external procedure convert_decoded_string_code39_to_code32.

Autodiscrimination

Autodiscrimination describes the simultaneous decoding of multiple bar code types in one call of find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code. For this purpose a tuple of bar code types is specified for the parameter CodeTypeCodeTypeCodeTypeCodeTypecodeTypecode_type. Using the generic value 'auto'"auto""auto""auto""auto""auto" all known bar code types are decoded - except 'PharmaCode'"PharmaCode""PharmaCode""PharmaCode""PharmaCode""PharmaCode" and 'MSI'"MSI""MSI""MSI""MSI""MSI" because these codes don't have enough features to be reliably separated from other bar code types. The tuple can also contain bar code types with the tilde prefix (~) which won't be decoded. For example ['auto'"auto""auto""auto""auto""auto", '~EAN-8'"~EAN-8""~EAN-8""~EAN-8""~EAN-8""~EAN-8", '~EAN-8 Add-On 2'"~EAN-8 Add-On 2""~EAN-8 Add-On 2""~EAN-8 Add-On 2""~EAN-8 Add-On 2""~EAN-8 Add-On 2", '~EAN-8 Add-On 5'"~EAN-8 Add-On 5""~EAN-8 Add-On 5""~EAN-8 Add-On 5""~EAN-8 Add-On 5""~EAN-8 Add-On 5"] describes all bar code types without 'PharmaCode'"PharmaCode""PharmaCode""PharmaCode""PharmaCode""PharmaCode", 'MSI'"MSI""MSI""MSI""MSI""MSI" and all kinds of 'EAN-8'"EAN-8""EAN-8""EAN-8""EAN-8""EAN-8". Please note that each additionally allowed bar code type increases the run-time of the operator. Using too many bar code types the reliability of the decoding could decrease because not all bar code types can be discriminated reliably. To improve autodiscrimination compatibility bar codes with a check character or check sum should be used.

The bar code reader tries to decode the bar code types in the following order:

'GS1 DataBar Omnidir'"GS1 DataBar Omnidir""GS1 DataBar Omnidir""GS1 DataBar Omnidir""GS1 DataBar Omnidir""GS1 DataBar Omnidir", 'GS1 DataBar Truncated'"GS1 DataBar Truncated""GS1 DataBar Truncated""GS1 DataBar Truncated""GS1 DataBar Truncated""GS1 DataBar Truncated", 'GS1 DataBar Stacked'"GS1 DataBar Stacked""GS1 DataBar Stacked""GS1 DataBar Stacked""GS1 DataBar Stacked""GS1 DataBar Stacked", 'GS1 DataBar Stacked Omnidir'"GS1 DataBar Stacked Omnidir""GS1 DataBar Stacked Omnidir""GS1 DataBar Stacked Omnidir""GS1 DataBar Stacked Omnidir""GS1 DataBar Stacked Omnidir", 'GS1 DataBar Limited'"GS1 DataBar Limited""GS1 DataBar Limited""GS1 DataBar Limited""GS1 DataBar Limited""GS1 DataBar Limited", 'GS1 DataBar Expanded'"GS1 DataBar Expanded""GS1 DataBar Expanded""GS1 DataBar Expanded""GS1 DataBar Expanded""GS1 DataBar Expanded", 'GS1 DataBar Expanded Stacked'"GS1 DataBar Expanded Stacked""GS1 DataBar Expanded Stacked""GS1 DataBar Expanded Stacked""GS1 DataBar Expanded Stacked""GS1 DataBar Expanded Stacked", 'GS1-128'"GS1-128""GS1-128""GS1-128""GS1-128""GS1-128", 'Code 128'"Code 128""Code 128""Code 128""Code 128""Code 128", 'EAN-13 Add-On 5'"EAN-13 Add-On 5""EAN-13 Add-On 5""EAN-13 Add-On 5""EAN-13 Add-On 5""EAN-13 Add-On 5", 'EAN-13 Add-On 2'"EAN-13 Add-On 2""EAN-13 Add-On 2""EAN-13 Add-On 2""EAN-13 Add-On 2""EAN-13 Add-On 2", 'EAN-13'"EAN-13""EAN-13""EAN-13""EAN-13""EAN-13", 'UPC-A Add-On 5'"UPC-A Add-On 5""UPC-A Add-On 5""UPC-A Add-On 5""UPC-A Add-On 5""UPC-A Add-On 5", 'UPC-A Add-On 2'"UPC-A Add-On 2""UPC-A Add-On 2""UPC-A Add-On 2""UPC-A Add-On 2""UPC-A Add-On 2", 'UPC-A'"UPC-A""UPC-A""UPC-A""UPC-A""UPC-A", 'EAN-8 Add-On 5'"EAN-8 Add-On 5""EAN-8 Add-On 5""EAN-8 Add-On 5""EAN-8 Add-On 5""EAN-8 Add-On 5", 'EAN-8 Add-On 2'"EAN-8 Add-On 2""EAN-8 Add-On 2""EAN-8 Add-On 2""EAN-8 Add-On 2""EAN-8 Add-On 2", 'EAN-8'"EAN-8""EAN-8""EAN-8""EAN-8""EAN-8", 'UPC-E Add-On 5'"UPC-E Add-On 5""UPC-E Add-On 5""UPC-E Add-On 5""UPC-E Add-On 5""UPC-E Add-On 5", 'UPC-E Add-On 2'"UPC-E Add-On 2""UPC-E Add-On 2""UPC-E Add-On 2""UPC-E Add-On 2""UPC-E Add-On 2", 'UPC-E'"UPC-E""UPC-E""UPC-E""UPC-E""UPC-E", 'Code 93'"Code 93""Code 93""Code 93""Code 93""Code 93", 'Code 39'"Code 39""Code 39""Code 39""Code 39""Code 39", 'Codabar'"Codabar""Codabar""Codabar""Codabar""Codabar", '2/5 Interleaved'"2/5 Interleaved""2/5 Interleaved""2/5 Interleaved""2/5 Interleaved""2/5 Interleaved", '2/5 Industrial'"2/5 Industrial""2/5 Industrial""2/5 Industrial""2/5 Industrial""2/5 Industrial"

Therefore you should exclude at least all definitely not occurring bar code types that are scanned before the first of the bar code types you expect to find or, better, just scan for the explicit list of bar code types you expect.

Especially for the autodiscrimination there is the operator set_bar_code_param_specificset_bar_code_param_specificSetBarCodeParamSpecificSetBarCodeParamSpecificSetBarCodeParamSpecificset_bar_code_param_specific. With it some parameters of the bar code model can be set specifically for certain bar code types.

Training

If the bar code reader is in training mode, the operator find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code executes a training cycle. The training mode is described with the operator set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param.

Timeout and Abort

The operator find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code can be aborted by a timeout and dynamically. With the operator set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param you can specify a timeout. If find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code reaches this timeout, it returns all codes decoded so far. Alternatively, you can call set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param with 'abort' from another thread to abort find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code dynamically.

The information whether the operator was aborted or not can be queried by calling get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultGetBarCodeResultget_bar_code_result with the parameter 'aborted'"aborted""aborted""aborted""aborted""aborted".

Furthermore, the operator find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code can be canceled, which means no result is returned but instead an error is returned. This can be done with the operator set_operator_timeoutset_operator_timeoutSetOperatorTimeoutSetOperatorTimeoutSetOperatorTimeoutset_operator_timeout or interrupt_operatorinterrupt_operatorInterruptOperatorInterruptOperatorInterruptOperatorinterrupt_operator. If find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code is canceled by set_operator_timeoutset_operator_timeoutSetOperatorTimeoutSetOperatorTimeoutSetOperatorTimeoutset_operator_timeout, H_ERR_TIMEOUT (9400) is returned. If find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code is canceled by interrupt_operatorinterrupt_operatorInterruptOperatorInterruptOperatorInterruptOperatorinterrupt_operator, H_ERR_CANCEL (22) is returned. Note: Both mentioned operators are only supported in cancel mode.

Advice on low resolution bar code imaging systems

This advice applies to bar code applications that use low resolution images, i.e., images in which a single bar is between 0.6 and 2 pixels wide.

In these cases, one should optimize the bar code imaging system in order to eliminate noise and focal blur because a combination of these optical distortions lead to problems in the decodability of low resolution bar codes.

See set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param documentation entry on 'small_elements_robustness'"small_elements_robustness""small_elements_robustness""small_elements_robustness""small_elements_robustness""small_elements_robustness" for more advice.

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 cancelling timeouts and interrupts.

This operator modifies the state of the following input parameter:

• BarCodeHandleBarCodeHandleBarCodeHandleBarCodeHandlebarCodeHandlebar_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)

* Small example for aborting bar code search:
read_image (Image, 'barcode/ean13/tea_box_10.png')

* Decode normally:
create_bar_code_model ([], [], BarCodeHandle)
find_bar_code (Image, SymbolRegions, BarCodeHandle, 'auto', \
    DecodedDataStrings)
stop ()

* Start bar code search in separate thread.
par_start<ThreadID>: find_bar_code (Image, SymbolRegions1, BarCodeHandle, \
    'auto', DecodedDataStrings1)

* Let some time pass.
wait_seconds (0.002)

* Abort the data code search.
set_bar_code_param (BarCodeHandle, 'abort', 'true')

* Wait for the thread, it should finish very fast.
par_join(ThreadID)

* We can determine that the search in fact was aborted.
get_bar_code_result (BarCodeHandle, 'all', 'aborted', Aborted)

Result

The operator find_bar_codefind_bar_codeFindBarCodeFindBarCodeFindBarCodefind_bar_code 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_modelCreateBarCodeModelCreateBarCodeModelCreateBarCodeModelcreate_bar_code_model, set_bar_code_paramset_bar_code_paramSetBarCodeParamSetBarCodeParamSetBarCodeParamset_bar_code_param

Possible Successors

get_bar_code_resultget_bar_code_resultGetBarCodeResultGetBarCodeResultGetBarCodeResultget_bar_code_result, get_bar_code_objectget_bar_code_objectGetBarCodeObjectGetBarCodeObjectGetBarCodeObjectget_bar_code_object, clear_bar_code_modelclear_bar_code_modelClearBarCodeModelClearBarCodeModelClearBarCodeModelclear_bar_code_model

Alternatives

decode_bar_code_rectangle2decode_bar_code_rectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2DecodeBarCodeRectangle2decode_bar_code_rectangle2

Module

Bar Code