/* * Copyright 2012 ZXing authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #import "ZXBitArray.h" #import "ZXEAN13Reader.h" #import "ZXErrors.h" #import "ZXIntArray.h" // For an EAN-13 barcode, the first digit is represented by the parities used // to encode the next six digits, according to the table below. For example, // if the barcode is 5 123456 789012 then the value of the first digit is // signified by using odd for '1', even for '2', even for '3', odd for '4', // odd for '5', and even for '6'. See http://en.wikipedia.org/wiki/EAN-13 // // Parity of next 6 digits // Digit 0 1 2 3 4 5 // 0 Odd Odd Odd Odd Odd Odd // 1 Odd Odd Even Odd Even Even // 2 Odd Odd Even Even Odd Even // 3 Odd Odd Even Even Even Odd // 4 Odd Even Odd Odd Even Even // 5 Odd Even Even Odd Odd Even // 6 Odd Even Even Even Odd Odd // 7 Odd Even Odd Even Odd Even // 8 Odd Even Odd Even Even Odd // 9 Odd Even Even Odd Even Odd // // Note that the encoding for '0' uses the same parity as a UPC barcode. Hence // a UPC barcode can be converted to an EAN-13 barcode by prepending a 0. // // The encoding is represented by the following array, which is a bit pattern // using Odd = 0 and Even = 1. For example, 5 is represented by: // // Odd Even Even Odd Odd Even // in binary: // 0 1 1 0 0 1 == 0x19 // const int ZX_EAN13_FIRST_DIGIT_ENCODINGS[] = { 0x00, 0x0B, 0x0D, 0xE, 0x13, 0x19, 0x1C, 0x15, 0x16, 0x1A }; @interface ZXEAN13Reader () @property (nonatomic, strong, readonly) ZXIntArray *decodeMiddleCounters; @end @implementation ZXEAN13Reader - (id)init { if (self = [super init]) { _decodeMiddleCounters = [[ZXIntArray alloc] initWithLength:4]; } return self; } - (int)decodeMiddle:(ZXBitArray *)row startRange:(NSRange)startRange result:(NSMutableString *)result error:(NSError **)error { ZXIntArray *counters = self.decodeMiddleCounters; [counters clear]; int end = row.size; int rowOffset = (int)NSMaxRange(startRange); int lgPatternFound = 0; for (int x = 0; x < 6 && rowOffset < end; x++) { int bestMatch = [ZXUPCEANReader decodeDigit:row counters:counters rowOffset:rowOffset patternType:ZX_UPC_EAN_PATTERNS_L_AND_G_PATTERNS error:error]; if (bestMatch == -1) { return -1; } [result appendFormat:@"%C", (unichar)('0' + bestMatch % 10)]; rowOffset += [counters sum]; if (bestMatch >= 10) { lgPatternFound |= 1 << (5 - x); } } if (![self determineFirstDigit:result lgPatternFound:lgPatternFound]) { if (error) *error = ZXNotFoundErrorInstance(); return -1; } NSRange middleRange = [[self class] findGuardPattern:row rowOffset:rowOffset whiteFirst:YES pattern:ZX_UPC_EAN_MIDDLE_PATTERN patternLen:ZX_UPC_EAN_MIDDLE_PATTERN_LEN error:error]; if (middleRange.location == NSNotFound) { return -1; } rowOffset = (int)NSMaxRange(middleRange); for (int x = 0; x < 6 && rowOffset < end; x++) { int bestMatch = [ZXUPCEANReader decodeDigit:row counters:counters rowOffset:rowOffset patternType:ZX_UPC_EAN_PATTERNS_L_PATTERNS error:error]; if (bestMatch == -1) { return -1; } [result appendFormat:@"%C", (unichar)('0' + bestMatch)]; rowOffset += [counters sum]; } return rowOffset; } - (ZXBarcodeFormat)barcodeFormat { return kBarcodeFormatEan13; } /** * Based on pattern of odd-even ('L' and 'G') patterns used to encoded the explicitly-encoded * digits in a barcode, determines the implicitly encoded first digit and adds it to the * result string. * * @param resultString string to insert decoded first digit into * @param lgPatternFound int whose bits indicates the pattern of odd/even L/G patterns used to * encode digits * @return NO if first digit cannot be determined */ - (BOOL)determineFirstDigit:(NSMutableString *)resultString lgPatternFound:(int)lgPatternFound { for (int d = 0; d < 10; d++) { if (lgPatternFound == ZX_EAN13_FIRST_DIGIT_ENCODINGS[d]) { [resultString insertString:[NSString stringWithFormat:@"%C", (unichar)('0' + d)] atIndex:0]; return YES; } } return NO; } @end