ClassesClasses | | Operators

find_data_code_2dT_find_data_code_2dFindDataCode2dFindDataCode2d (Operator)


find_data_code_2dT_find_data_code_2dFindDataCode2dFindDataCode2d — Detect and read 2D data code symbols in an image or train the 2D data code model.


find_data_code_2d(Image : SymbolXLDs : DataCodeHandle, GenParamName, GenParamValue : ResultHandles, DecodedDataStrings)

Herror T_find_data_code_2d(const Hobject Image, Hobject* SymbolXLDs, const Htuple DataCodeHandle, const Htuple GenParamName, const Htuple GenParamValue, Htuple* ResultHandles, Htuple* DecodedDataStrings)

void FindDataCode2d(const HObject& Image, HObject* SymbolXLDs, const HTuple& DataCodeHandle, const HTuple& GenParamName, const HTuple& GenParamValue, HTuple* ResultHandles, HTuple* DecodedDataStrings)

HXLDCont HDataCode2D::FindDataCode2d(const HImage& Image, const HTuple& GenParamName, const HTuple& GenParamValue, HTuple* ResultHandles, HTuple* DecodedDataStrings) const

HXLDCont HDataCode2D::FindDataCode2d(const HImage& Image, const HString& GenParamName, Hlong GenParamValue, Hlong* ResultHandles, HString* DecodedDataStrings) const

HXLDCont HDataCode2D::FindDataCode2d(const HImage& Image, const char* GenParamName, Hlong GenParamValue, Hlong* ResultHandles, HString* DecodedDataStrings) const

HXLDCont HImage::FindDataCode2d(const HDataCode2D& DataCodeHandle, const HTuple& GenParamName, const HTuple& GenParamValue, HTuple* ResultHandles, HTuple* DecodedDataStrings) const

HXLDCont HImage::FindDataCode2d(const HDataCode2D& DataCodeHandle, const HString& GenParamName, Hlong GenParamValue, Hlong* ResultHandles, HString* DecodedDataStrings) const

HXLDCont HImage::FindDataCode2d(const HDataCode2D& DataCodeHandle, const char* GenParamName, Hlong GenParamValue, Hlong* ResultHandles, HString* DecodedDataStrings) const

static void HOperatorSet.FindDataCode2d(HObject image, out HObject symbolXLDs, HTuple dataCodeHandle, HTuple genParamName, HTuple genParamValue, out HTuple resultHandles, out HTuple decodedDataStrings)

HXLDCont HDataCode2D.FindDataCode2d(HImage image, HTuple genParamName, HTuple genParamValue, out HTuple resultHandles, out HTuple decodedDataStrings)

HXLDCont HDataCode2D.FindDataCode2d(HImage image, string genParamName, int genParamValue, out int resultHandles, out string decodedDataStrings)

HXLDCont HImage.FindDataCode2d(HDataCode2D dataCodeHandle, HTuple genParamName, HTuple genParamValue, out HTuple resultHandles, out HTuple decodedDataStrings)

HXLDCont HImage.FindDataCode2d(HDataCode2D dataCodeHandle, string genParamName, int genParamValue, out int resultHandles, out string decodedDataStrings)


The operator find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d detects 2D data code symbols in the input image (ImageImageImageImageimage) and reads the data that is encoded in the symbol. Before calling find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d, a model of a class of 2D data codes that matches the symbols in the images must be created with create_data_code_2d_modelcreate_data_code_2d_modelCreateDataCode2dModelCreateDataCode2dModelCreateDataCode2dModel or read_data_code_2d_modelread_data_code_2d_modelReadDataCode2dModelReadDataCode2dModelReadDataCode2dModel. The handle returned by these operators is passed to find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d in DataCodeHandleDataCodeHandleDataCodeHandleDataCodeHandledataCodeHandle. To look for more than one symbol in an image, the generic parameter 'stop_after_result_num'"stop_after_result_num""stop_after_result_num""stop_after_result_num""stop_after_result_num" can be passed to GenParamNameGenParamNameGenParamNameGenParamNamegenParamName together with the number of requested symbols as GenParamValueGenParamValueGenParamValueGenParamValuegenParamValue.

As a result the operator returns for every successfully decoded symbol the surrounding XLD contour (SymbolXLDsSymbolXLDsSymbolXLDsSymbolXLDssymbolXLDs), a result handle, which refers to a candidate structure that stores additional information about the symbol as well as the search and decoding process (ResultHandlesResultHandlesResultHandlesResultHandlesresultHandles), and the string that is encoded in the symbol (DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStrings). Passing the candidate handle from ResultHandlesResultHandlesResultHandlesResultHandlesresultHandles together with the generic parameter 'decoded_data'"decoded_data""decoded_data""decoded_data""decoded_data", get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults returns a tuple with the ASCII code of all characters of the string (see also Tuple / String Operations).

For an explanation of the concept of the 2D data code reader see the introduction of chapter Identification / Data Code.

The symbol structure of GS1 DataMatrix, GS1 QR Code, and GS1 Aztec is identical to the structure of ECC 200, QR Code, and Aztec Code, respectively. Therefore, all parameters, settings, and rules applying to ECC 200, QR Code, or Aztec Code apply to their GS1 variants as well. The GS1 symbologies enforce merely additional rules for the format of the data carried by the codes. The data has to be organized in so called GS1 application element strings according to the GS1 General Specifications. For example, if the data code model DataCodeHandleDataCodeHandleDataCodeHandleDataCodeHandledataCodeHandle is created as GS1 DataMatrix, then find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d only returns a result if the underlying symbol is a valid ECC 200 symbol, and only if its data conforms to the GS1 application element strings rules. For the GS1 application element strings it is only checked if the application identifiers exist in the GS1 General Specifications. In contrast, find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d will return no results for ECC 200 containing general data. The same is valid for GS1 QR Code and GS1 Aztec Code.

Adjusting the model

If there is a symbol in the image that cannot be read, it should be verified, whether the properties of the symbol fit the model parameters. Special attention should be paid to

Further relevant parameters are the gap between neighboring foreground modules and, for ECC 200, the maximum slant of the L-shaped finder pattern ('slant_max'"slant_max""slant_max""slant_max""slant_max"). The current settings for these parameters are returned by the operator get_data_code_2d_paramget_data_code_2d_paramGetDataCode2dParamGetDataCode2dParamGetDataCode2dParam. If necessary, the corresponding model parameters can be adjusted with set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam.

It is recommended to adjust the model as well as possible to the symbols in the images also for runtime reasons. In general, the runtime of find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d is higher for a more general model than for a more specific model. One should take into account that a general model leads to a high runtime especially if no valid data code can be found.

Train the model

Besides setting the model parameters manually with set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam, the model can also be trained with find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d based on one or several sample images. For this, the generic parameter 'train'"train""train""train""train" must be passed in GenParamNameGenParamNameGenParamNameGenParamNamegenParamName. The corresponding value passed in GenParamValueGenParamValueGenParamValueGenParamValuegenParamValue determines the model parameters that should be learned. The following values are possible:

It is possible to train several of these parameters in one call of find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d by passing the generic parameter 'train'"train""train""train""train" in a tuple more than once in conjunction with the corresponding parameters: e.g., GenParamNameGenParamNameGenParamNameGenParamNamegenParamName = ['train','train']["train","train"]["train","train"]["train","train"]["train","train"] and GenParamValueGenParamValueGenParamValueGenParamValuegenParamValue = ['polarity','module_size']["polarity","module_size"]["polarity","module_size"]["polarity","module_size"]["polarity","module_size"]. Furthermore, in conjunction with 'train'"train""train""train""train" = 'all'"all""all""all""all" it is possible to exclude single parameters from training explicitly again by passing 'train'"train""train""train""train" more than once. The names of the parameters to exclude, however, must be prefixed by '~'"~""~""~""~": GenParamNameGenParamNameGenParamNameGenParamNamegenParamName = ['train','train']["train","train"]["train","train"]["train","train"]["train","train"] and GenParamValueGenParamValueGenParamValueGenParamValuegenParamValue = ['all','~contrast']["all","~contrast"]["all","~contrast"]["all","~contrast"]["all","~contrast"], e.g., trains all parameters except the minimum contrast.

For training the model, the following aspects should be considered:

Note that during training, a possibly set timeout is ignored (see set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam).

Functionality of the symbol search

Depending on the current settings of the 2D data code model (see set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam), the operator find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d performs several passes for searching the data code symbols. The search starts at the highest pyramid level, where - according to the maximum module size defined in the data code model - the modules can be separated. In addition, in every pyramid level the preprocessing can vary depending on the presets for the module gap. If the data code model enables dark symbols on a light background as well as light symbols on a dark background, within the current pyramid level, the dark symbols are searched first. Then the passes for searching light symbols follow. A pass consists of two phases: The search phase is used to look for the finder patterns and to generate a symbol candidate for every detected finder pattern, and the evaluation phase, where in a lower pyramid level all candidates are investigated and - if possible - read.

The operator call is either terminated after successfully decoding the requested number of symbols, after processing all search passes, or due to a timeout (see set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam). The number of requested symbols can be specified via the generic parameter GenParamNameGenParamNameGenParamNameGenParamNamegenParamName = 'stop_after_result_num'"stop_after_result_num""stop_after_result_num""stop_after_result_num""stop_after_result_num". Without specifying this number the search stops as soon as one symbol could be decoded.

Query results of the symbol search

With the result handles and the operators get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults and get_data_code_2d_objectsget_data_code_2d_objectsGetDataCode2dObjectsGetDataCode2dObjectsGetDataCode2dObjects, additional data can be requested about the search process, e.g., the number of internal search passes or the number of investigated candidates, and - together with the ResultHandlesResultHandlesResultHandlesResultHandlesresultHandles - about the symbols, like the symbol and module size, the contrast, or the raw data coded in the symbol. In addition, these operators provide information about all investigated candidates that could not be read. In particular, this helps to determine if a candidate was actually generated at the symbol's position during the preprocessing and - by the value of a status variable - why the search or reading was aborted. Further information about the parameters can be found with the operators get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults and get_data_code_2d_objectsget_data_code_2d_objectsGetDataCode2dObjectsGetDataCode2dObjectsGetDataCode2dObjects.

Timeout and Abort

The operator find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d can be aborted by a timeout and dynamically. With the operator set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam you can specify a timeout. If find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d reaches this timeout, it returns all codes decoded so far. Alternatively, you can call set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam with 'abort' from another thread to abort find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d dynamically.

The information whether the operator was aborted or not can be queried by calling get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults with the parameter 'aborted'"aborted""aborted""aborted""aborted".

Chinese characters

If a QR Code contains Chinese characters encoded according to the Chinese national standard GBT 18284-2000, find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d returns these characters UTF-8 encoded in DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStrings, if the system parameter 'filename_encoding'"filename_encoding""filename_encoding""filename_encoding""filename_encoding" is set to 'utf8'"utf8""utf8""utf8""utf8". The contents of 'decoded_data'"decoded_data""decoded_data""decoded_data""decoded_data", which can be retrieved with get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults, are never converted to UTF-8.

Execution Information


ImageImageImageImageimage (input_object)  singlechannelimage objectHImageHImageHobject (byte)

Input image. If the image has a reduced domain, the data code search is reduced to that domain. This usually reduces the runtime of the operator. However, if the datacode is not fully inside the domain, the datacode might not be found correctly. In rare cases, data codes may be found outside the domain. If these results are undesirable, they have to be subsequently eliminated.

SymbolXLDsSymbolXLDsSymbolXLDsSymbolXLDssymbolXLDs (output_object)  xld_cont(-array) objectHXLDContHXLDContHobject *

XLD contours that surround the successfully decoded data code symbols. The order of the contour points reflects the orientation of the detected symbols. The contours begin in the top left corner (see 'orientation' at get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults) and continue clockwise.

DataCodeHandleDataCodeHandleDataCodeHandleDataCodeHandledataCodeHandle (input_control)  datacode_2d HDataCode2D, HTupleHTupleHtuple (handle) (IntPtr) (HHandle) (handle)

Handle of the 2D data code model.

GenParamNameGenParamNameGenParamNameGenParamNamegenParamName (input_control) HTupleHTupleHtuple (string) (string) (HString) (char*)

Names of (optional) parameters for controlling the behavior of the operator.

Default value: []

List of values: 'stop_after_result_num'"stop_after_result_num""stop_after_result_num""stop_after_result_num""stop_after_result_num", 'train'"train""train""train""train"

GenParamValueGenParamValueGenParamValueGenParamValuegenParamValue (input_control)  attribute.value(-array) HTupleHTupleHtuple (integer / real / string) (int / long / double / string) (Hlong / double / HString) (Hlong / double / char*)

Values of the optional generic parameters.

Default value: []

Suggested values: 'all'"all""all""all""all", 'model_type'"model_type""model_type""model_type""model_type", 'symbol_size'"symbol_size""symbol_size""symbol_size""symbol_size", 'version'"version""version""version""version", 'module_size'"module_size""module_size""module_size""module_size", 'small_modules_robustness'"small_modules_robustness""small_modules_robustness""small_modules_robustness""small_modules_robustness", 'module_shape'"module_shape""module_shape""module_shape""module_shape", 'polarity'"polarity""polarity""polarity""polarity", 'mirrored'"mirrored""mirrored""mirrored""mirrored", 'contrast'"contrast""contrast""contrast""contrast", 'module_grid'"module_grid""module_grid""module_grid""module_grid", 'finder_pattern_tolerance'"finder_pattern_tolerance""finder_pattern_tolerance""finder_pattern_tolerance""finder_pattern_tolerance", 'contrast_tolerance'"contrast_tolerance""contrast_tolerance""contrast_tolerance""contrast_tolerance", 'additional_levels'"additional_levels""additional_levels""additional_levels""additional_levels", 'image_proc'"image_proc""image_proc""image_proc""image_proc", 1, 2, 3

ResultHandlesResultHandlesResultHandlesResultHandlesresultHandles (output_control)  integer(-array) HTupleHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Handles of all successfully decoded 2D data code symbols.

DecodedDataStringsDecodedDataStringsDecodedDataStringsDecodedDataStringsdecodedDataStrings (output_control)  string(-array) HTupleHTupleHtuple (string) (string) (HString) (char*)

Decoded data strings of all detected 2D data code symbols in the image.

Example (HDevelop)

* Examples showing the use of find_data_code_2d.
* First, the operator is used to train the model, afterwards it is used to
* read the symbol in another image.

* Create a model for reading Data matrix ECC 200 codes
create_data_code_2d_model ('Data Matrix ECC 200', [], [], DataCodeHandle)
* Read a training image
read_image (Image, 'datacode/ecc200/ecc200_cpu_008')
* Train the model with the symbol in the image
find_data_code_2d (Image, SymbolXLDs, DataCodeHandle, 'train', 'all', \
                   ResultHandles, DecodedDataStrings)
* End of training / begin of normal application

* Read an image
read_image (Image, 'datacode/ecc200/ecc200_cpu_010')
* Read the symbol in the image
find_data_code_2d (Image, SymbolXLDs, DataCodeHandle, [], [], \
                   ResultHandles, DecodedDataStrings)

* Display all symbols, the strings encoded in them, and the module size
dev_set_color ('green')
for i := 0 to |ResultHandles| - 1 by 1
    select_obj (SymbolXLDs, SymbolXLD, i+1)
    dev_display (SymbolXLD)
    get_contour_xld (SymbolXLD, Row, Col)
    set_tposition (WindowHandle, max(Row), min(Col))
    write_string (WindowHandle, DecodedDataStrings[i])
    get_data_code_2d_results (DataCodeHandle, ResultHandles[i], \
                              ['module_height','module_width'], ModuleSize)
    new_line (WindowHandle)
    write_string (WindowHandle, 'module size = ' + ModuleSize[0] + 'x' + \

* Clear the model
clear_data_code_2d_model (DataCodeHandle)


The operator find_data_code_2dfind_data_code_2dFindDataCode2dFindDataCode2dFindDataCode2d returns the value 2 (H_MSG_TRUE) if the given parameters are correct. Otherwise, an exception is raised.

Possible Predecessors

create_data_code_2d_modelcreate_data_code_2d_modelCreateDataCode2dModelCreateDataCode2dModelCreateDataCode2dModel, read_data_code_2d_modelread_data_code_2d_modelReadDataCode2dModelReadDataCode2dModelReadDataCode2dModel, set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam

Possible Successors

get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults, get_data_code_2d_objectsget_data_code_2d_objectsGetDataCode2dObjectsGetDataCode2dObjectsGetDataCode2dObjects, write_data_code_2d_modelwrite_data_code_2d_modelWriteDataCode2dModelWriteDataCode2dModelWriteDataCode2dModel

See also

create_data_code_2d_modelcreate_data_code_2d_modelCreateDataCode2dModelCreateDataCode2dModelCreateDataCode2dModel, set_data_code_2d_paramset_data_code_2d_paramSetDataCode2dParamSetDataCode2dParamSetDataCode2dParam, get_data_code_2d_resultsget_data_code_2d_resultsGetDataCode2dResultsGetDataCode2dResultsGetDataCode2dResults, get_data_code_2d_objectsget_data_code_2d_objectsGetDataCode2dObjectsGetDataCode2dObjectsGetDataCode2dObjects


GS1 General Specifications; Version 12; Issue 1, Jan-2012; GS1.


Data Code

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