unprintable-character.md

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default-layout	How to Handle Non-printable Characters Like "\u{1D}" or "{GS}" from the Barcode Text?	Dynamsoft Barcode Reader, FAQ, tech basic, enable DPM	How to Handle Non-printable Characters Like "\u{1D}" or "{GS}" from the Barcode Text?	false	/faq/general/unprintable-character.html

How to Handle Non-printable Characters Like "\u{1D}" or "{GS}" from the Barcode Text?

This page helps to you modify the barcode results when non-printable characters exists in the barcode text you decoded.

You always get 2 values that stands for the barcode decoding result from the CBarcodeResultItem object:

• barcodeBytes
• barcodeText

Since barcodeText is a string value that generated from the barcodeBytes, is might be decoded into different characters based on different character encoding formats. When there exists a non-printable ASCII value (0 ~ 31 or 127) in the barcodeBytes array, the value is decoded into a messy code. Currently, the library doesn't provide methods to remove the non-printable characters nor convert them into printable characters, you have to add your own code to recognize the non-printable characters and replace or remove them. The following code snippet is an example for how to create a method for processing the barcodeBytes into a string you want.

Code Snippet

>- C++ >- Android >- Objective-C >- Swift > > ```c++ #include #include typedef enum ProcessNonPrintingCharsMode { PNPCM_KEEP, PNPCM_REMOVE, PNPCM_CONVERT }ProcessNonPrintingCharsMode; class ProcessBarcodeBytesUtil { private: std::map charValueToStringDict; public: ProcessBarcodeBytesUtil() { int NonPrintingAsciiCharsValue[33] = { 0x0,0x1,0x2,0x3,0x4,0x5,0x6,0x7,0x8,0x9,0xa,0xb,0xc,0xd,0xe,0xf,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1a,0x1b,0x1c,0x1d,0x1e,0x1f,0x7f }; const char* NonPrintingAsciiCharsString[33] = { "{NUL}","{SOH}","{STX}","{ETX}","{EOT}","{ENQ}","{ACK}","{BEL}","{BS}","{HT}","{LF}","{VT}","{FF}","{CR}","{SO}","{SI}","{DLE}","{DC1}","{DC2}","{DC3}","{DC4}","{NAK}","{SYN}","{ETB}","{CAN}","{EM}","{SUB}","{ESC}","{FS}","{GS}","{RS}","{US}","{DEL}" }; for (int i = 0; i < 33; ++i) charValueToStringDict.insert(std::make_pair(NonPrintingAsciiCharsValue[i], NonPrintingAsciiCharsString[i])); } /** * Process the non-printing chars of barcode bytes to obtain desired text. * * @param [in] bytes The barcode content in a byte array. * @param [in] bytesLength The length of the byte array. * @param [in] mode The mode indicates how to processing non-printing chars. * @param [in] keepLineBreak The flag indicates whether to preserve the original line breaks in the resulting text. It is only valid when mode is PNPCM_REMOVE or PNPCM_CONVERT. * * @return Returns The text result after processing barcode bytes. * */ std::string processBarcodeBytes(unsigned char* bytes, int bytesLength, ProcessNonPrintingCharsMode mode, bool keepLineBreak = true) { std::string result; for (int i = 0; i < bytesLength; ++i) { int byteValue = (int)bytes[i]; if (charValueToStringDict.find(byteValue) == charValueToStringDict.end() || mode == PNPCM_KEEP || keepLineBreak && (byteValue == 10 || byteValue == 13)) { result.append(1, bytes[i]); } else if (mode == PNPCM_CONVERT) { result.append(charValueToStringDict[byteValue]); } } return result; } }; int main() { // obtain bytes from CBarcodeResultItem. unsigned char* barcodeBytes = barcodeResult->GetBytes(); int bytesLength = barcodeResult->GetBytesLength(); ProcessBarcodeBytesUtil util; std::string originStr = util.processBarcodeBytes(barcodeBytes, bytesLength, PNPCM_KEEP); std::cout << "1.original text:" << std::endl << originStr << std::endl << std::endl; std::string strAfterRemoveExceptLineBreack = util.processBarcodeBytes(barcodeBytes, bytesLength, PNPCM_REMOVE); std::cout << "2.text after removing non-printing chars except line break:" << std::endl << strAfterRemoveExceptLineBreack << std::endl << std::endl; std::string strAfterRemove= util.processBarcodeBytes(barcodeBytes, bytesLength, PNPCM_REMOVE, false); std::cout << "3.text after removing non-printing chars:" << std::endl << strAfterRemove << std::endl << std::endl; std::string strAfterConvertExceptLineBreack = util.processBarcodeBytes(barcodeBytes, bytesLength, PNPCM_CONVERT); std::cout << "4.text after converting non-printing chars except line break:" << std::endl << strAfterConvertExceptLineBreack << std::endl << std::endl; std::string strAfterConvert = util.processBarcodeBytes(barcodeBytes, bytesLength, PNPCM_CONVERT, false); std::cout << "5.text after converting non-printing chars:" << std::endl << strAfterConvert << std::endl << std::endl; return 0; } ``` > ```java mRouter.addResultReceiver(new CapturedResultReceiver() { @Override // Implement the callback method to receive DecodedBarcodesResult. // The method returns a DecodedBarcodesResult object that contains an array of BarcodeResultItems. // BarcodeResultItems is the basic unit from which you can get the basic info of the barcode like the barcode text and barcode format. public void onDecodedBarcodesReceived(DecodedBarcodesResult result) { process = new ProcessBarcodeResultUtil(); if (result!=null && result.getItems().length!=0){ for (int i=0; i< result.getItems().length; i++){ // The return value is the modified barcode text. String processedResult = process.processBarcodeByte(result.getItems().getBytes(),ProcessBarcodeResultUtil.ProcessNonPrintingCharsMode.PNPCM_REMOVE,true); Log.i("ProcessByte", "onDecodedBarcodesReceived: processeResult = "+processedResult); } } } }); // Create a ProcessBarcodeResultUtil class public class ProcessBarcodeResultUtil { enum ProcessNonPrintingCharsMode{ PNPCM_KEEP, PNPCM_REMOVE, PNPCM_CONVERT } final HashMap charValueToStringDict = new HashMap(); ProcessBarcodeResultUtil(){ final int[] NonPrintingAsciiCharsValue = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,127}; final String[] NonPrintingAsciiCharsString = { "{NUL}","{SOH}","{STX}","{ETX}","{EOT}","{ENQ}","{ACK}","{BEL}","{BS}","{HT}","{LF}","{VT}","{FF}","{CR}","{SO}","{SI}", "{DLE}","{DC1}","{DC2}","{DC3}","{DC4}","{NAK}","{SYN}","{ETB}","{CAN}","{EM}","{SUB}","{ESC}","{FS}","{GS}","{RS}","{US}","{DEL}" }; for (int i = 0; i < 33; ++i){ charValueToStringDict.put(NonPrintingAsciiCharsValue[i], NonPrintingAsciiCharsString[i]); } } public String processBarcodeByte(byte[] barcodeByte, ProcessNonPrintingCharsMode mode, boolean keepLineBreak){ StringBuilder processedResult = new StringBuilder(); for (int i=0; i ```objc typedef NS_ENUM(NSInteger,EnumResultProcessMode) { RPM_KEEP = 0, RPM_CONVERT = 1, RPM_REMOVE = 2 }; ... - (void)onDecodedBarcodesReceived:(DSDecodedBarcodesResult *)result { if (result.items.count > 0) { for (DSBarcodeResultItem *item in result.items) { NSString *modifiedBarcodeText = [self processResult:item.bytes mode:RPM_CONVERT isBreaklineKept:NO]; msgText = [msgText stringByAppendingString:[NSString stringWithFormat:@"\nFormat: %@\nText: %@\n", item.formatString, modifiedBarcodeText]]; } } } - (NSString *)processBarcodeBytes:(NSData *)byte mode:(EnumResultProcessMode)mode isBreaklineKept:(BOOL)isKept{ NSArray* _nonPrintingAsciiCharsKey = @[@0,@1,@2,@3,@4,@5,@6,@7,@8,@9,@10,@11,@12,@13,@14,@15,@16,@17,@18,@19,@20,@21,@22,@23,@24,@25,@26,@27,@28,@29,@30,@31,@127]; NSArray* _nonPrintingAsciiCharsString = @[@"{NUL}",@"{SOH}",@"{STX}",@"{ETX}",@"{EOT}",@"{ENQ}",@"{ACK}",@"{BEL}",@"{BS}",@"{HT}",@"{LF}",@"{VT}",@"{FF}",@"{CR}",@"{SO}",@"{SI}",@"{DLE}",@"{DC1}",@"{DC2}",@"{DC3}",@"{DC4}",@"{NAK}",@"{SYN}",@"{ETB}",@"{CAN}",@"{EM}",@"{SUB}",@"{ESC}",@"{FS}",@"{GS}",@"{RS}",@"{US}",@"{DEL}"]; NSMapTable * _charValueToStringDict = [NSMapTable strongToStrongObjectsMapTable]; for (int i=0; i<_nonPrintingAsciiCharsKey.count;i++){ [_charValueToStringDict setObject:_nonPrintingAsciiCharsString[i] forKey:_nonPrintingAsciiCharsKey[i]]; } const char* _Nonnull barcodeByteChar = byte.bytes; NSString *processedText = @""; for (int i=0;i31 && (int)barcodeByteChar[i]!=127 && (int)barcodeByteChar[i]!=0)){ NSString *nextString = [NSString stringWithFormat:@"%c",barcodeByteChar[i]]; processedText = [processedText stringByAppendingString:nextString]; } else if (mode == RPM_CONVERT){ NSNumber *keyValue = [[NSNumber alloc] initWithInt:(int)barcodeByteChar[i]]; NSString *nextString = [_charValueToStringDict objectForKey:@2]; processedText = [processedText stringByAppendingString:nextString]; } } return processedText; } ``` > ```swift enum EnumResultProcessMode{ case keep case convert case remove } func onDecodedBarcodesReceived(_ result: DecodedBarcodesResult) { if let items = result.items, items.count > 0 { for item in items { let processedBarcodeText = processBarcodeBytes(byte: item.bytes, processMode: EnumResultProcessMode.convert, isKeep: true) item.barcodeText = processedBarcodeText } } } private func processBarcodeBytes(byte:Data, processMode:EnumResultProcessMode, isKeep:Bool) -> String{ let charValueToStringDict:NSDictionary = [0:"{NUL}",1:"{SOH}",2:"{STX}",3:"{ETX}",4:"{EOT}",5:"{ENQ}",6:"{ACK}",7:"{BEL}",8:"{BS}",9:"{HT}",10:"{LF}",11:"{VT}",12:"{FF}",13:"{CR}",14:"{SO}",15:"{SI}",16:"{DLE}",17:"{DC1}",18:"{DC2}",19:"{DC3}",20:"{DC4}",21:"{NAK}",22:"{SYN}",23:"{ETB}",24:"{CAN}",25:"{EM}",26:"{SUB}",27:"{ESC}",28:"{FS}",29:"{GS}",30:"{RS}",31:"{US}",127:"{DEL}"] var processedString = "" for i in 0...byte.count-1{ if ((isKeep && ((byte[i]==10) || (byte[i]==13))) || (processMode == EnumResultProcessMode.keep) || ((byte[i]>31) && (byte[i] != 127) && (byte[i] != 0))){ let nextText:String = String(bytes: [byte[i]], encoding: String.Encoding.utf8)! processedString += nextText as String } else if (processMode == EnumResultProcessMode.convert){ let nextText:NSString = charValueToStringDict.object(forKey: byte[i]) as! NSString processedString += nextText as String } } return processedString } ```