aistudio-wpf-diagram/zxing.core/xx/oned/MultiFormatUPCEANReader.cs

/*
 * Copyright 2008 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.
 */

using System.Collections.Generic;
using ZXing.Common;

namespace ZXing.OneD
{
   /// <summary>
   ///   <p>A reader that can read all available UPC/EAN formats. If a caller wants to try to
   /// read all such formats, it is most efficient to use this implementation rather than invoke
   /// individual readers.</p>
   ///   <author>Sean Owen</author>
   /// </summary>
   public sealed class MultiFormatUPCEANReader : OneDReader
   {
      private readonly UPCEANReader[] readers;

      /// <summary>
      /// Initializes a new instance of the <see cref="MultiFormatUPCEANReader"/> class.
      /// </summary>
      /// <param name="hints">The hints.</param>
      public MultiFormatUPCEANReader(IDictionary<DecodeHintType, object> hints)
      {
         var possibleFormats = hints == null || !hints.ContainsKey(DecodeHintType.POSSIBLE_FORMATS) ? null :
             (IList<BarcodeFormat>)hints[DecodeHintType.POSSIBLE_FORMATS];
         var readers = new List<UPCEANReader>();
         if (possibleFormats != null)
         {
            if (possibleFormats.Contains(BarcodeFormat.EAN_13) || possibleFormats.Contains(BarcodeFormat.All_1D))
            {
               readers.Add(new EAN13Reader());
            }
            else if (possibleFormats.Contains(BarcodeFormat.UPC_A) || possibleFormats.Contains(BarcodeFormat.All_1D))
            {
               readers.Add(new UPCAReader());
            }
            if (possibleFormats.Contains(BarcodeFormat.EAN_8) || possibleFormats.Contains(BarcodeFormat.All_1D))
            {
               readers.Add(new EAN8Reader());
            }
            if (possibleFormats.Contains(BarcodeFormat.UPC_E) || possibleFormats.Contains(BarcodeFormat.All_1D))
            {
               readers.Add(new UPCEReader());
            }
         }
         if (readers.Count == 0)
         {
            readers.Add(new EAN13Reader());
            // UPC-A is covered by EAN-13
            readers.Add(new EAN8Reader());
            readers.Add(new UPCEReader());
         }
         this.readers = readers.ToArray();
      }

      /// <summary>
      ///   <p>Attempts to decode a one-dimensional barcode format given a single row of
      /// an image.</p>
      /// </summary>
      /// <param name="rowNumber">row number from top of the row</param>
      /// <param name="row">the black/white pixel data of the row</param>
      /// <param name="hints">decode hints</param>
      /// <returns>
      ///   <see cref="Result"/>containing encoded string and start/end of barcode or null if an error occurs or barcode cannot be found
      /// </returns>
      override public Result decodeRow(int rowNumber,
                              BitArray row,
                              IDictionary<DecodeHintType, object> hints)
      {
         // Compute this location once and reuse it on multiple implementations
         int[] startGuardPattern = UPCEANReader.findStartGuardPattern(row);
         if (startGuardPattern == null)
            return null;

         foreach (UPCEANReader reader in readers)
         {
            Result result = reader.decodeRow(rowNumber, row, startGuardPattern, hints);
            if (result == null)
               continue;

            // Special case: a 12-digit code encoded in UPC-A is identical to a "0"
            // followed by those 12 digits encoded as EAN-13. Each will recognize such a code,
            // UPC-A as a 12-digit string and EAN-13 as a 13-digit string starting with "0".
            // Individually these are correct and their readers will both read such a code
            // and correctly call it EAN-13, or UPC-A, respectively.
            //
            // In this case, if we've been looking for both types, we'd like to call it
            // a UPC-A code. But for efficiency we only run the EAN-13 decoder to also read
            // UPC-A. So we special case it here, and convert an EAN-13 result to a UPC-A
            // result if appropriate.
            //
            // But, don't return UPC-A if UPC-A was not a requested format!
            bool ean13MayBeUPCA =
                result.BarcodeFormat == BarcodeFormat.EAN_13 &&
                    result.Text[0] == '0';
            var possibleFormats =
                hints == null || !hints.ContainsKey(DecodeHintType.POSSIBLE_FORMATS) ? null : (IList<BarcodeFormat>)hints[DecodeHintType.POSSIBLE_FORMATS];
            bool canReturnUPCA = possibleFormats == null || possibleFormats.Contains(BarcodeFormat.UPC_A) || possibleFormats.Contains(BarcodeFormat.All_1D);

            if (ean13MayBeUPCA && canReturnUPCA)
            {
               // Transfer the metdata across
               var resultUPCA = new Result(result.Text.Substring(1),
                                              result.RawBytes,
                                              result.ResultPoints,
                                              BarcodeFormat.UPC_A);
               resultUPCA.putAllMetadata(result.ResultMetadata);
               return resultUPCA;
            }
            return result;
         }

         return null;
      }

      /// <summary>
      /// Resets any internal state the implementation has after a decode, to prepare it
      /// for reuse.
      /// </summary>
      public override void reset()
      {
         foreach (Reader reader in readers)
         {
            reader.reset();
         }
      }
   }
}