Read Damaged Barcodes

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Barcode Images with Gaussian Noise

Gaussian noise is one of the most common damages that may deteriorate the quality of a source barcode. Most difficulties correspond to the cases when barcode images have a monochrome color scheme or the distortion grain is considerably bigger than the minimal element of a barcode. To cope with these effects, median filtering mechanisms suitable for both 1D and 2D types can be applied. Median filtering mechanisms also affect image quality due to the possible removal of some barcode elements together with noise; however, they still may be helpful in improving the readability of key barcode modules.

If you need any clarifications, feel free to reach out to Aspose Technical Support: ask your questions at Aspose.Barcode Forum or contact Aspose Paid Support Helpdesk.

Median Filtering for 2D Barcodes

In Aspose.BarCode for PHP via Java, median filtering can be implemented using the setAllowMedianSmoothing function and setting the median filtering window using the setMedianSmoothingWindowSize function of class QualitySettings. Unlike 1D barcodes, automated selection of a suitable median filtering window is not supported for 2D types.

$reader = new BarCodeReader("test.png", DecodeType::CODE_39_STANDARD, DecodeType::CODE_128);
$reader->getQualitySettings()->setAllowMedianSmoothing(true);
$reader->getQualitySettings()->setMedianSmoothingWindowSize(5);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Median Filtering for 1D Barcodes

One-dimensional filtering for linear barcodes can be enabled using the setAllowSaltAndPaperFiltering function. The filtering window size is selected automatically.

$reader = new BarCodeReader("test.png", DecodeType::CODE_128);
$reader->getQualitySettings()->setAllowSaltAndPaperFiltering(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Median Filtering for Postal Barcodes

One-dimensional median filtering for postal barcode types can be performed using the AllowMicroWhiteSpotsRemoving function. The size of the filtering window is set automatically.

$reader = new BarCodeReader("test.png", DecodeType::PLANET);
$reader->getQualitySettings()->setAllowMicroWhiteSpotsRemoving(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Filtering Out White Spots

The presence of white spots in barcode images is a frequent problem that appears while sending documents with barcodes through fax transmission. To mitigate this issue, it is possible to use the setAllowWhiteSpotsRemoving function, which allows filtering out not all Gaussian noise but only white spots.

$reader = new BarCodeReader("test.png", DecodeType::CODE_128);
$reader->getQualitySettings()->setAllowWhiteSpotsRemoving(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reducing Barcode Image Size to Eliminate Visual Artifacts

In some cases, distortions caused by excessive scaling of a barcode image can be mitigated by reducing the scale space. It can be done using the setAllowDecreasedImage function. Its purpose is to reduce the size of an image and in this way, to facilitate barcode reading by eliminating visual artifacts.

$reader = new BarCodeReader("test.png", DecodeType::DATA_MATRIX);
$reader->getQualitySettings()->setAllowDecreasedImage(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reading Inverted Barcode Images

The barcode library enables reading barcode images with inverted colors. To do this, it is required to enable the setAllowInvertImage function.

$reader = new BarCodeReader("test.png", DecodeType::AZTEC);
$reader->getQualitySettings()->setAllowInvertImage(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Detecting Colored Barcodes on Colored Background

To read colored barcodes on a colored background, it is necessary to use the setAllowComplexBackground function that attempts to distinguish the colored background from barcode labels through color quantization and then subtract it. It should be noted that enabling this parameter results in considerable deceleration of recognition speed and thus should be used in special cases only.

$reader = new BarCodeReader("test.png", DecodeType::QR);
$reader->getQualitySettings()->setAllowComplexBackground(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reading Barcodes with Erased or Displaced Bars

While scanning or sending barcode images using fax transmission, the problem of displaced or erased bars in 1D barcode labels often appears, especially, in those printed out using ink-jet printers. To resolve this issue, the barcode library provides two functions called setAllowOneDWipedBarsRestoration and setCheckMore1DVariants, which allow selecting the most suitable recognition option according to the checksum value and other barcode elements. However, it should be noted that enabling these settings may result in incorrect recognition of 1D barcodes.

$reader = new BarCodeReader("test.png", DecodeType::CODE_128);
$reader->getQualitySettings()->setAllowOneDWipedBarsRestoration(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reading Evidently Incorrect Barcodes

In cases when it is necessary just to detect the presence of barcodes regardless of their validity and corresponding recognition correctness, it is possible to enable two special settings called setAllowIncorrectBarcodes and setReadTinyBarcodes. The first one is used to attempt performing partial barcode recognition even if the reading process has provided incorrect results; in this case, the barcode data is decoded with BarCodeConfidence being set to NONE, which means that the correctness of recognition is not guaranteed.

The setReadTinyBarcodes function facilitates reading small barcode labels in large images. It is ignored if the setAllowIncorrectBarcodes function is called passing the True value. However, enabling this parameter may result in recognizing false barcodes in place of actual text or tables.

$reader = new BarCodeReader("test.png", DecodeType::QR, DecodeType::PDF417);
$reader->getQualitySettings()->setAllowIncorrectBarcodes(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

$reader = new BarCodeReader("test.png", DecodeType::QR, DecodeType::PDF417);
$reader->getQualitySettings()->setReadTinyBarcodes(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reading Severely Distorted QR Codes and Micro QR Codes

The barcode library allows reading severely corrupted QR Code and Micro QR Code labels. This can be enabled by setting the setAllowQRMicroQrRestoration parameter.

$reader = new BarCodeReader("test.png", DecodeType::QR);
$reader->getQualitySettings()->setAllowQRMicroQrRestoration(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());

Reading Industrial Data Matrix Barcodes

Industrial Data Matrix barcodes often have dotted patterns or other decoration elements and are placed onto metallic surfaces, in this way, creating embossed indelible barcode labels. To facilitate the recognition of such barcodes, it is possible to enable the setAllowDatamatrixIndustrialBarcodes function, which allows reading dashed labels in a slow mode.

$reader = new BarCodeReader("test.png", DecodeType::DATA_MATRIX);
$reader->getQualitySettings()->setAllowDatamatrixIndustrialBarcodes(true);
foreach($reader->readBarCodes() as $result)
  print("BarCode CodeText: ".$result->getCodeText());