X-Git-Url: http://git.rot13.org/?a=blobdiff_plain;f=core%2Fsrc%2Fcom%2Fgoogle%2Fzxing%2Fqrcode%2Fdecoder%2FFormatInformation.java;h=1b76b0de56e39f2fe0640541fb8a0ea8e1b1fd46;hb=feb768bba4b752ffe9ae48f6460675280517ec16;hp=223474600346a634f815c960fe105113b22fb33d;hpb=b675ea978c21ce2e8dac27c63a09057561945d16;p=zxing.git diff --git a/core/src/com/google/zxing/qrcode/decoder/FormatInformation.java b/core/src/com/google/zxing/qrcode/decoder/FormatInformation.java index 22347460..1b76b0de 100644 --- a/core/src/com/google/zxing/qrcode/decoder/FormatInformation.java +++ b/core/src/com/google/zxing/qrcode/decoder/FormatInformation.java @@ -1,5 +1,5 @@ /* - * Copyright 2007 Google Inc. + * Copyright 2007 ZXing authors * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -16,13 +16,11 @@ package com.google.zxing.qrcode.decoder; -import com.google.zxing.ReaderException; - /** *
Encapsulates a QR Code's format information, including the data mask used and * error correction level.
* - * @author srowen@google.com (Sean Owen) + * @author Sean Owen * @see DataMask * @see ErrorCorrectionLevel */ @@ -33,7 +31,7 @@ final class FormatInformation { /** * See ISO 18004:2006, Annex C, Table C.1 */ - private static final int[][] FORMAT_INFO_DECODE_LOOKUP = new int[][]{ + private static final int[][] FORMAT_INFO_DECODE_LOOKUP = { {0x5412, 0x00}, {0x5125, 0x01}, {0x5E7C, 0x02}, @@ -72,12 +70,12 @@ final class FormatInformation { * Offset i holds the number of 1 bits in the binary representation of i */ private static final int[] BITS_SET_IN_HALF_BYTE = - new int[]{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4}; + {0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4}; private final ErrorCorrectionLevel errorCorrectionLevel; private final byte dataMask; - private FormatInformation(int formatInfo) throws ReaderException { + private FormatInformation(int formatInfo) { // Bits 3,4 errorCorrectionLevel = ErrorCorrectionLevel.forBits((formatInfo >> 3) & 0x03); // Bottom 3 bits @@ -98,39 +96,51 @@ final class FormatInformation { } /** - * @param rawFormatInfo - * @return + * @param maskedFormatInfo1 format info indicator, with mask still applied + * @param maskedFormatInfo2 second copy of same info; both are checked at the same time + * to establish best match + * @return information about the format it specifies, ornull
+ * if doesn't seem to match any known pattern
*/
- static FormatInformation decodeFormatInformation(int rawFormatInfo) throws ReaderException {
- FormatInformation formatInfo = doDecodeFormatInformation(rawFormatInfo);
+ static FormatInformation decodeFormatInformation(int maskedFormatInfo1, int maskedFormatInfo2) {
+ FormatInformation formatInfo = doDecodeFormatInformation(maskedFormatInfo1, maskedFormatInfo2);
if (formatInfo != null) {
return formatInfo;
}
// Should return null, but, some QR codes apparently
- // do not mask this info. Try again, first masking the raw bits so
- // the function will unmask
- return doDecodeFormatInformation(rawFormatInfo ^ FORMAT_INFO_MASK_QR);
+ // do not mask this info. Try again by actually masking the pattern
+ // first
+ return doDecodeFormatInformation(maskedFormatInfo1 ^ FORMAT_INFO_MASK_QR,
+ maskedFormatInfo2 ^ FORMAT_INFO_MASK_QR);
}
- private static FormatInformation doDecodeFormatInformation(int rawFormatInfo) throws ReaderException {
- // Unmask:
- int unmaskedFormatInfo = rawFormatInfo ^ FORMAT_INFO_MASK_QR;
+ private static FormatInformation doDecodeFormatInformation(int maskedFormatInfo1, int maskedFormatInfo2) {
// Find the int in FORMAT_INFO_DECODE_LOOKUP with fewest bits differing
int bestDifference = Integer.MAX_VALUE;
int bestFormatInfo = 0;
for (int i = 0; i < FORMAT_INFO_DECODE_LOOKUP.length; i++) {
int[] decodeInfo = FORMAT_INFO_DECODE_LOOKUP[i];
int targetInfo = decodeInfo[0];
- if (targetInfo == unmaskedFormatInfo) {
+ if (targetInfo == maskedFormatInfo1 || targetInfo == maskedFormatInfo2) {
// Found an exact match
return new FormatInformation(decodeInfo[1]);
}
- int bitsDifference = numBitsDiffering(unmaskedFormatInfo, targetInfo);
+ int bitsDifference = numBitsDiffering(maskedFormatInfo1, targetInfo);
if (bitsDifference < bestDifference) {
bestFormatInfo = decodeInfo[1];
bestDifference = bitsDifference;
}
+ if (maskedFormatInfo1 != maskedFormatInfo2) {
+ // also try the other option
+ bitsDifference = numBitsDiffering(maskedFormatInfo2, targetInfo);
+ if (bitsDifference < bestDifference) {
+ bestFormatInfo = decodeInfo[1];
+ bestDifference = bitsDifference;
+ }
+ }
}
+ // Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits
+ // differing means we found a match
if (bestDifference <= 3) {
return new FormatInformation(bestFormatInfo);
}