Support mirrored QR codes

git-svn-id: https://zxing.googlecode.com/svn/trunk@2815 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/multi/qrcode/QRCodeMultiReader.java

@@ -29,6 +29,7 @@ import com.google.zxing.common.DetectorResult;
 import com.google.zxing.multi.MultipleBarcodeReader;
 import com.google.zxing.multi.qrcode.detector.MultiDetector;
 import com.google.zxing.qrcode.QRCodeReader;
+import com.google.zxing.qrcode.decoder.QRCodeDecoderMetaData;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -57,6 +58,10 @@ public final class QRCodeMultiReader extends QRCodeReader implements MultipleBar
       try {
         DecoderResult decoderResult = getDecoder().decode(detectorResult.getBits(), hints);
         ResultPoint[] points = detectorResult.getPoints();
+        // If the code was mirrored: swap the bottom-left and the top-right points.
+        if (decoderResult.getOther() instanceof QRCodeDecoderMetaData) {
+          ((QRCodeDecoderMetaData) decoderResult.getOther()).applyMirroredCorrection(points);
+        }
         Result result = new Result(decoderResult.getText(), decoderResult.getRawBytes(), points,
                                    BarcodeFormat.QR_CODE);
         List<byte[]> byteSegments = decoderResult.getByteSegments();

core/src/com/google/zxing/qrcode/QRCodeReader.java

@@ -30,6 +30,7 @@ import com.google.zxing.common.BitMatrix;
 import com.google.zxing.common.DecoderResult;
 import com.google.zxing.common.DetectorResult;
 import com.google.zxing.qrcode.decoder.Decoder;
+import com.google.zxing.qrcode.decoder.QRCodeDecoderMetaData;
 import com.google.zxing.qrcode.detector.Detector;
 
 import java.util.List;
@@ -78,6 +79,11 @@ public class QRCodeReader implements Reader {
       points = detectorResult.getPoints();
     }
 
+    // If the code was mirrored: swap the bottom-left and the top-right points.
+    if (decoderResult.getOther() instanceof QRCodeDecoderMetaData) {
+      ((QRCodeDecoderMetaData) decoderResult.getOther()).applyMirroredCorrection(points);
+    }
+
     Result result = new Result(decoderResult.getText(), decoderResult.getRawBytes(), points, BarcodeFormat.QR_CODE);
     List<byte[]> byteSegments = decoderResult.getByteSegments();
     if (byteSegments != null) {

core/src/com/google/zxing/qrcode/decoder/BitMatrixParser.java

@@ -27,6 +27,7 @@ final class BitMatrixParser {
   private final BitMatrix bitMatrix;
   private Version parsedVersion;
   private FormatInformation parsedFormatInfo;
+  private boolean mirror;
 
   /**
    * @param bitMatrix {@link BitMatrix} to parse
@@ -137,12 +138,13 @@ final class BitMatrixParser {
   }
 
   private int copyBit(int i, int j, int versionBits) {
-    return bitMatrix.get(i, j) ? (versionBits << 1) | 0x1 : versionBits << 1;
+    boolean bit = mirror ? bitMatrix.get(j, i) : bitMatrix.get(i, j);
+    return bit ? (versionBits << 1) | 0x1 : versionBits << 1;
   }
 
   /**
    * <p>Reads the bits in the {@link BitMatrix} representing the finder pattern in the
-   * correct order in order to reconstitute the codewords bytes contained within the
+   * correct order in order to reconstruct the codewords bytes contained within the
    * QR Code.</p>
    *
    * @return bytes encoded within the QR Code
@@ -155,7 +157,7 @@ final class BitMatrixParser {
 
     // Get the data mask for the format used in this QR Code. This will exclude
     // some bits from reading as we wind through the bit matrix.
-    DataMask dataMask = DataMask.forReference((int) formatInfo.getDataMask());
+    DataMask dataMask = DataMask.forReference(formatInfo.getDataMask());
     int dimension = bitMatrix.getHeight();
     dataMask.unmaskBitMatrix(bitMatrix, dimension);
 
@@ -202,4 +204,42 @@ final class BitMatrixParser {
     return result;
   }
 
-}
+  /**
+   * Revert the mask removal done while reading the code words. The bit matrix should revert to its original state.
+   */
+  void remask() {
+    if (parsedFormatInfo == null) {
+      return; // We have no format information, and have no data mask
+    }
+    DataMask dataMask = DataMask.forReference(parsedFormatInfo.getDataMask());
+    int dimension = bitMatrix.getHeight();
+    dataMask.unmaskBitMatrix(bitMatrix, dimension);
+  }
+
+  /**
+   * Prepare the parser for a mirrored operation.
+   * This flag has effect only on the {@link #readFormatInformation()} and the
+   * {@link #readVersion()}. Before proceeding with {@link #readCodewords()} the
+   * {@link #mirror()} method should be called.
+   * 
+   * @param mirror Whether to read version and format information mirrored.
+   */
+  void setMirror(boolean mirror) {
+    parsedVersion = null;
+    parsedFormatInfo = null;
+    this.mirror = mirror;
+  }
+
+  /** Mirror the bit matrix in order to attempt a second reading. */
+  void mirror() {
+    for (int x = 0; x < bitMatrix.getWidth(); x++) {
+      for (int y = x + 1; y < bitMatrix.getHeight(); y++) {
+        if (bitMatrix.get(x, y) != bitMatrix.get(y, x)) {
+          bitMatrix.flip(y, x);
+          bitMatrix.flip(x, y);          
+        }
+      }
+    }
+  }
+
+}

core/src/com/google/zxing/qrcode/decoder/Decoder.java

@@ -85,6 +85,71 @@ public final class Decoder {
 
     // Construct a parser and read version, error-correction level
     BitMatrixParser parser = new BitMatrixParser(bits);
+    FormatException fe = null;
+    ChecksumException ce = null;
+    try {
+      return decode(parser, hints);
+    } catch (FormatException e) {
+      fe = e;
+    } catch (ChecksumException e) {
+      ce = e;
+    }
+
+    try {
+
+      // Revert the bit matrix
+      parser.remask();
+
+      // Will be attempting a mirrored reading of the version and format info.
+      parser.setMirror(true);
+
+      // Preemptively read the version.
+      parser.readVersion();
+
+      // Preemptively read the format information.
+      parser.readFormatInformation();
+
+      /*
+       * Since we're here, this means we have successfully detected some kind
+       * of version and format information when mirrored. This is a good sign,
+       * that the QR code may be mirrored, and we should try once more with a
+       * mirrored content.
+       */
+      // Prepare for a mirrored reading.
+      parser.mirror();
+
+      DecoderResult result = decode(parser, hints);
+
+      // Success! Notify the caller that the code was mirrored.
+      result.setOther(new QRCodeDecoderMetaData(true));
+
+      return result;
+
+    } catch (FormatException e) {
+      // Throw the exception from the original reading
+      if (fe != null) {
+        throw fe;
+      }
+      if (ce != null) {
+        throw ce;
+      }
+      throw e;
+
+    } catch (ChecksumException e) {
+      // Throw the exception from the original reading
+      if (fe != null) {
+        throw fe;
+      }
+      if (ce != null) {
+        throw ce;
+      }
+      throw e;
+
+    }
+  }
+
+  private DecoderResult decode(BitMatrixParser parser, Map<DecodeHintType,?> hints)
+      throws FormatException, ChecksumException {
     Version version = parser.readVersion();
     ErrorCorrectionLevel ecLevel = parser.readFormatInformation().getErrorCorrectionLevel();
 

core/src/com/google/zxing/qrcode/decoder/QRCodeDecoderMetaData.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2013 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.
+ */
+
+package com.google.zxing.qrcode.decoder;
+
+import com.google.zxing.ResultPoint;
+
+/**
+ * Meta-data container for QR Code decoding. Instances of this class may be used to convey information back to the
+ * decoding caller. Callers are expected to process this.
+ * 
+ * @see com.google.zxing.common.DecoderResult#getOther()
+ */
+public final class QRCodeDecoderMetaData {
+
+  private final boolean mirrored;
+  
+  QRCodeDecoderMetaData(boolean mirrored) {
+    this.mirrored = mirrored;
+  }
+
+  /** 
+   * @return true if the QR Code was mirrored. 
+   */
+  public boolean isMirrored() {
+    return mirrored;
+  }
+
+  /**
+   * Apply the result points' order correction due to mirroring.
+   * 
+   * @param points Array of points to apply mirror correction to.
+   */
+  public void applyMirroredCorrection(ResultPoint[] points) {
+    if (!mirrored || points == null || points.length < 3) {
+      return;
+    }
+    ResultPoint bottomLeft = points[0];
+    points[0] = points[2];
+    points[2] = bottomLeft;
+    // No need to 'fix' top-left and alignment pattern.
+  }
+
+}