csharp/qrcode/decoder/Decoder.cs

   1 /*\r
   2 * Copyright 2007 ZXing authors\r
   3 *\r
   4 * Licensed under the Apache License, Version 2.0 (the "License");\r
   5 * you may not use this file except in compliance with the License.\r
   6 * You may obtain a copy of the License at\r
   7 *\r
   8 *      http://www.apache.org/licenses/LICENSE-2.0\r
   9 *\r
  10 * Unless required by applicable law or agreed to in writing, software\r
  11 * distributed under the License is distributed on an "AS IS" BASIS,\r
  12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
  13 * See the License for the specific language governing permissions and\r
  14 * limitations under the License.\r
  15 */\r
  16 using System;\r
  17 using ReaderException = com.google.zxing.ReaderException;\r
  18 using BitMatrix = com.google.zxing.common.BitMatrix;\r
  19 using DecoderResult = com.google.zxing.common.DecoderResult;\r
  20 using GF256 = com.google.zxing.common.reedsolomon.GF256;\r
  21 using ReedSolomonDecoder = com.google.zxing.common.reedsolomon.ReedSolomonDecoder;\r
  22 using ReedSolomonException = com.google.zxing.common.reedsolomon.ReedSolomonException;\r
  23 namespace com.google.zxing.qrcode.decoder\r
  24 {\r
  25         \r
  26         /// <summary> <p>The main class which implements QR Code decoding -- as opposed to locating and extracting\r
  27         /// the QR Code from an image.</p>\r
  28         /// \r
  29         /// </summary>\r
  30         /// <author>  Sean Owen\r
  31         /// </author>\r
  32         /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source \r
  33         /// </author>\r
  34         public sealed class Decoder\r
  35         {\r
  36                 \r
  37                 //UPGRADE_NOTE: Final was removed from the declaration of 'rsDecoder '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  38                 private ReedSolomonDecoder rsDecoder;\r
  39                 \r
  40                 public Decoder()\r
  41                 {\r
  42                         rsDecoder = new ReedSolomonDecoder(GF256.QR_CODE_FIELD);\r
  43                 }\r
  44                 \r
  45                 /// <summary> <p>Convenience method that can decode a QR Code represented as a 2D array of booleans.\r
  46                 /// "true" is taken to mean a black module.</p>\r
  47                 /// \r
  48                 /// </summary>\r
  49                 /// <param name="image">booleans representing white/black QR Code modules\r
  50                 /// </param>\r
  51                 /// <returns> text and bytes encoded within the QR Code\r
  52                 /// </returns>\r
  53                 /// <throws>  ReaderException if the QR Code cannot be decoded </throws>\r
  54                 public DecoderResult decode(bool[][] image)\r
  55                 {\r
  56                         int dimension = image.Length;\r
  57                         BitMatrix bits = new BitMatrix(dimension);\r
  58                         for (int i = 0; i < dimension; i++)\r
  59                         {\r
  60                                 for (int j = 0; j < dimension; j++)\r
  61                                 {\r
  62                                         if (image[i][j])\r
  63                                         {\r
  64                                                 bits.set_Renamed(j, i);\r
  65                                         }\r
  66                                 }\r
  67                         }\r
  68                         return decode(bits);\r
  69                 }\r
  70                 \r
  71                 /// <summary> <p>Decodes a QR Code represented as a {@link BitMatrix}. A 1 or "true" is taken to mean a black module.</p>\r
  72                 /// \r
  73                 /// </summary>\r
  74                 /// <param name="bits">booleans representing white/black QR Code modules\r
  75                 /// </param>\r
  76                 /// <returns> text and bytes encoded within the QR Code\r
  77                 /// </returns>\r
  78                 /// <throws>  ReaderException if the QR Code cannot be decoded </throws>\r
  79                 public DecoderResult decode(BitMatrix bits)\r
  80                 {\r
  81                         \r
  82                         // Construct a parser and read version, error-correction level\r
  83                         BitMatrixParser parser = new BitMatrixParser(bits);\r
  84                         Version version = parser.readVersion();\r
  85                         ErrorCorrectionLevel ecLevel = parser.readFormatInformation().ErrorCorrectionLevel;\r
  86                         \r
  87                         // Read codewords\r
  88                         sbyte[] codewords = parser.readCodewords();\r
  89                         // Separate into data blocks\r
  90                         DataBlock[] dataBlocks = DataBlock.getDataBlocks(codewords, version, ecLevel);\r
  91                         \r
  92                         // Count total number of data bytes\r
  93                         int totalBytes = 0;\r
  94                         for (int i = 0; i < dataBlocks.Length; i++)\r
  95                         {\r
  96                                 totalBytes += dataBlocks[i].NumDataCodewords;\r
  97                         }\r
  98                         sbyte[] resultBytes = new sbyte[totalBytes];\r
  99                         int resultOffset = 0;\r
 100                         \r
 101                         // Error-correct and copy data blocks together into a stream of bytes\r
 102                         for (int j = 0; j < dataBlocks.Length; j++)\r
 103                         {\r
 104                                 DataBlock dataBlock = dataBlocks[j];\r
 105                                 sbyte[] codewordBytes = dataBlock.Codewords;\r
 106                                 int numDataCodewords = dataBlock.NumDataCodewords;\r
 107                                 correctErrors(codewordBytes, numDataCodewords);\r
 108                                 for (int i = 0; i < numDataCodewords; i++)\r
 109                                 {\r
 110                                         resultBytes[resultOffset++] = codewordBytes[i];\r
 111                                 }\r
 112                         }\r
 113                         \r
 114                         // Decode the contents of that stream of bytes\r
 115                         return DecodedBitStreamParser.decode(resultBytes, version, ecLevel);\r
 116                 }\r
 117                 \r
 118                 /// <summary> <p>Given data and error-correction codewords received, possibly corrupted by errors, attempts to\r
 119                 /// correct the errors in-place using Reed-Solomon error correction.</p>\r
 120                 /// \r
 121                 /// </summary>\r
 122                 /// <param name="codewordBytes">data and error correction codewords\r
 123                 /// </param>\r
 124                 /// <param name="numDataCodewords">number of codewords that are data bytes\r
 125                 /// </param>\r
 126                 /// <throws>  ReaderException if error correction fails </throws>\r
 127                 private void  correctErrors(sbyte[] codewordBytes, int numDataCodewords)\r
 128                 {\r
 129                         int numCodewords = codewordBytes.Length;\r
 130                         // First read into an array of ints\r
 131                         int[] codewordsInts = new int[numCodewords];\r
 132                         for (int i = 0; i < numCodewords; i++)\r
 133                         {\r
 134                                 codewordsInts[i] = codewordBytes[i] & 0xFF;\r
 135                         }\r
 136                         int numECCodewords = codewordBytes.Length - numDataCodewords;\r
 137                         try\r
 138                         {\r
 139                                 rsDecoder.decode(codewordsInts, numECCodewords);\r
 140                         }\r
 141                         catch (ReedSolomonException rse)\r
 142                         {\r
 143                                 throw ReaderException.Instance;\r
 144                         }\r
 145                         // Copy back into array of bytes -- only need to worry about the bytes that were data\r
 146                         // We don't care about errors in the error-correction codewords\r
 147                         for (int i = 0; i < numDataCodewords; i++)\r
 148                         {\r
 149                                 codewordBytes[i] = (sbyte) codewordsInts[i];\r
 150                         }\r
 151                 }\r
 152         }\r
 153 }