添加项目文件。

zxing.core/xx/pdf417/decoder/ec/ErrorCorrection.cs

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+/*
+ * 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.
+ */
+
+namespace ZXing.PDF417.Internal.EC
+{
+   /// <summary>
+   /// <p>PDF417 error correction implementation.</p>
+   /// <p>This <a href="http://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction#Example">example</a>
+   /// is quite useful in understanding the algorithm.</p>
+   /// <author>Sean Owen</author>
+   /// <see cref="ZXing.Common.ReedSolomon.ReedSolomonDecoder" />
+   /// </summary>
+   public sealed class ErrorCorrection
+   {
+      private readonly ModulusGF field;
+
+      /// <summary>
+      /// Initializes a new instance of the <see cref="ErrorCorrection"/> class.
+      /// </summary>
+      public ErrorCorrection()
+      {
+         this.field = ModulusGF.PDF417_GF;
+      }
+
+      /// <summary>
+      /// Decodes the specified received.
+      /// </summary>
+      /// <param name="received">received codewords</param>
+      /// <param name="numECCodewords">number of those codewords used for EC</param>
+      /// <param name="erasures">location of erasures</param>
+      /// <param name="errorLocationsCount">The error locations count.</param>
+      /// <returns></returns>
+      public bool decode(int[] received, int numECCodewords, int[] erasures, out int errorLocationsCount)
+      {
+         ModulusPoly poly = new ModulusPoly(field, received);
+         int[] S = new int[numECCodewords];
+         bool error = false;
+         errorLocationsCount = 0;
+         for (int i = numECCodewords; i > 0; i--)
+         {
+            int eval = poly.evaluateAt(field.exp(i));
+            S[numECCodewords - i] = eval;
+            if (eval != 0)
+            {
+               error = true;
+            }
+         }
+
+         if (!error)
+         {
+            return true;
+         }
+
+         ModulusPoly knownErrors = field.One;
+         if (erasures != null)
+         {
+            foreach (int erasure in erasures)
+            {
+               int b = field.exp(received.Length - 1 - erasure);
+               // Add (1 - bx) term:
+               ModulusPoly term = new ModulusPoly(field, new int[] {field.subtract(0, b), 1});
+               knownErrors = knownErrors.multiply(term);
+            }
+         }
+
+         ModulusPoly syndrome = new ModulusPoly(field, S);
+         //syndrome = syndrome.multiply(knownErrors);
+
+         ModulusPoly[] sigmaOmega = runEuclideanAlgorithm(field.buildMonomial(numECCodewords, 1), syndrome, numECCodewords);
+
+         if (sigmaOmega == null)
+         {
+            return false;
+         }
+
+         ModulusPoly sigma = sigmaOmega[0];
+         ModulusPoly omega = sigmaOmega[1];
+
+         if (sigma == null || omega == null)
+         {
+            return false;
+         }
+
+         //sigma = sigma.multiply(knownErrors);
+
+         int[] errorLocations = findErrorLocations(sigma);
+
+         if (errorLocations == null)
+         {
+            return false;
+         }
+
+         int[] errorMagnitudes = findErrorMagnitudes(omega, sigma, errorLocations);
+
+         for (int i = 0; i < errorLocations.Length; i++)
+         {
+            int position = received.Length - 1 - field.log(errorLocations[i]);
+            if (position < 0)
+            {
+               return false;
+
+            }
+            received[position] = field.subtract(received[position], errorMagnitudes[i]);
+         }
+         errorLocationsCount = errorLocations.Length;
+         return true;
+      }
+
+      /// <summary>
+      /// Runs the euclidean algorithm (Greatest Common Divisor) until r's degree is less than R/2
+      /// </summary>
+      /// <returns>The euclidean algorithm.</returns>
+      private ModulusPoly[] runEuclideanAlgorithm(ModulusPoly a, ModulusPoly b, int R)
+      {
+         // Assume a's degree is >= b's
+         if (a.Degree < b.Degree)
+         {
+            ModulusPoly temp = a;
+            a = b;
+            b = temp;
+         }
+
+         ModulusPoly rLast = a;
+         ModulusPoly r = b;
+         ModulusPoly tLast = field.Zero;
+         ModulusPoly t = field.One;
+
+         // Run Euclidean algorithm until r's degree is less than R/2
+         while (r.Degree >= R / 2)
+         {
+            ModulusPoly rLastLast = rLast;
+            ModulusPoly tLastLast = tLast;
+            rLast = r;
+            tLast = t;
+
+            // Divide rLastLast by rLast, with quotient in q and remainder in r
+            if (rLast.isZero)
+            {
+               // Oops, Euclidean algorithm already terminated?
+               return null;
+            }
+            r = rLastLast;
+            ModulusPoly q = field.Zero;
+            int denominatorLeadingTerm = rLast.getCoefficient(rLast.Degree);
+            int dltInverse = field.inverse(denominatorLeadingTerm);
+            while (r.Degree >= rLast.Degree && !r.isZero)
+            {
+               int degreeDiff = r.Degree - rLast.Degree;
+               int scale = field.multiply(r.getCoefficient(r.Degree), dltInverse);
+               q = q.add(field.buildMonomial(degreeDiff, scale));
+               r = r.subtract(rLast.multiplyByMonomial(degreeDiff, scale));
+            }
+
+            t = q.multiply(tLast).subtract(tLastLast).getNegative();
+         }
+
+         int sigmaTildeAtZero = t.getCoefficient(0);
+         if (sigmaTildeAtZero == 0)
+         {
+            return null;
+         }
+
+         int inverse = field.inverse(sigmaTildeAtZero);
+         ModulusPoly sigma = t.multiply(inverse);
+         ModulusPoly omega = r.multiply(inverse);
+         return new ModulusPoly[] { sigma, omega };
+      }
+
+      /// <summary>
+      /// Finds the error locations as a direct application of Chien's search
+      /// </summary>
+      /// <returns>The error locations.</returns>
+      /// <param name="errorLocator">Error locator.</param>
+      private int[] findErrorLocations(ModulusPoly errorLocator)
+      {
+         // This is a direct application of Chien's search
+         int numErrors = errorLocator.Degree;
+         int[] result = new int[numErrors];
+         int e = 0;
+         for (int i = 1; i < field.Size && e < numErrors; i++)
+         {
+            if (errorLocator.evaluateAt(i) == 0)
+            {
+               result[e] = field.inverse(i);
+               e++;
+            }
+         }
+         if (e != numErrors)
+         {
+            return null;
+         }
+         return result;
+      }
+
+      /// <summary>
+      /// Finds the error magnitudes by directly applying Forney's Formula
+      /// </summary>
+      /// <returns>The error magnitudes.</returns>
+      /// <param name="errorEvaluator">Error evaluator.</param>
+      /// <param name="errorLocator">Error locator.</param>
+      /// <param name="errorLocations">Error locations.</param>
+      private int[] findErrorMagnitudes(ModulusPoly errorEvaluator,
+                                        ModulusPoly errorLocator,
+                                        int[] errorLocations)
+      {
+         int errorLocatorDegree = errorLocator.Degree;
+         int[] formalDerivativeCoefficients = new int[errorLocatorDegree];
+         for (int i = 1; i <= errorLocatorDegree; i++)
+         {
+            formalDerivativeCoefficients[errorLocatorDegree - i] =
+                field.multiply(i, errorLocator.getCoefficient(i));
+         }
+         ModulusPoly formalDerivative = new ModulusPoly(field, formalDerivativeCoefficients);
+
+         // This is directly applying Forney's Formula
+         int s = errorLocations.Length;
+         int[] result = new int[s];
+         for (int i = 0; i < s; i++)
+         {
+            int xiInverse = field.inverse(errorLocations[i]);
+            int numerator = field.subtract(0, errorEvaluator.evaluateAt(xiInverse));
+            int denominator = field.inverse(formalDerivative.evaluateAt(xiInverse));
+            result[i] = field.multiply(numerator, denominator);
+         }
+         return result;
+      }
+   }
+}

zxing.core/xx/pdf417/decoder/ec/ModulusGF.cs

@@ -0,0 +1,121 @@
+/*
+ * 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.
+ */
+
+using System;
+
+namespace ZXing.PDF417.Internal.EC
+{
+   /// <summary>
+   /// <p>A field based on powers of a generator integer, modulo some modulus.</p>
+   /// @see com.google.zxing.common.reedsolomon.GenericGF
+   /// </summary>
+   /// <author>Sean Owen</author>
+   internal sealed class ModulusGF
+   {
+      public static ModulusGF PDF417_GF = new ModulusGF(PDF417Common.NUMBER_OF_CODEWORDS, 3);
+
+      private readonly int[] expTable;
+      private readonly int[] logTable;
+      public ModulusPoly Zero { get; private set; }
+      public ModulusPoly One { get; private set; }
+      private readonly int modulus;
+
+      public ModulusGF(int modulus, int generator)
+      {
+         this.modulus = modulus;
+         expTable = new int[modulus];
+         logTable = new int[modulus];
+         int x = 1;
+         for (int i = 0; i < modulus; i++)
+         {
+            expTable[i] = x;
+            x = (x * generator) % modulus;
+         }
+         for (int i = 0; i < modulus - 1; i++)
+         {
+            logTable[expTable[i]] = i;
+         }
+         // logTable[0] == 0 but this should never be used
+         Zero = new ModulusPoly(this, new int[] {0});
+         One = new ModulusPoly(this, new int[] {1});
+      }
+
+      internal ModulusPoly buildMonomial(int degree, int coefficient)
+      {
+         if (degree < 0)
+         {
+            throw new ArgumentException();
+         }
+         if (coefficient == 0)
+         {
+            return Zero;
+         }
+         int[] coefficients = new int[degree + 1];
+         coefficients[0] = coefficient;
+         return new ModulusPoly(this, coefficients);
+      }
+
+      internal int add(int a, int b)
+      {
+         return (a + b)%modulus;
+      }
+
+      internal int subtract(int a, int b)
+      {
+         return (modulus + a - b)%modulus;
+      }
+
+      internal int exp(int a)
+      {
+         return expTable[a];
+      }
+
+      internal int log(int a)
+      {
+         if (a == 0)
+         {
+            throw new ArgumentException();
+         }
+         return logTable[a];
+      }
+
+      internal int inverse(int a)
+      {
+         if (a == 0)
+         {
+            throw new ArithmeticException();
+         }
+         return expTable[modulus - logTable[a] - 1];
+      }
+
+      internal int multiply(int a, int b)
+      {
+         if (a == 0 || b == 0)
+         {
+            return 0;
+         }
+         return expTable[(logTable[a] + logTable[b]) % (modulus - 1)];
+      }
+
+      internal int Size
+      {
+         get
+         {
+            return modulus;
+         }
+      }
+   }
+}

zxing.core/xx/pdf417/decoder/ec/ModulusPoly.cs

@@ -0,0 +1,366 @@
+/*
+ * 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.
+ */
+
+using System;
+using System.Text;
+
+namespace ZXing.PDF417.Internal.EC
+{
+   /// <summary>
+   /// <see cref="com.google.zxing.common.reedsolomon.GenericGFPoly"/>
+   /// </summary>
+   /// <author>Sean Owen</author>
+   internal sealed class ModulusPoly
+   {
+      private readonly ModulusGF field;
+      private readonly int[] coefficients;
+
+      public ModulusPoly(ModulusGF field, int[] coefficients)
+      {
+         if (coefficients.Length == 0)
+         {
+            throw new ArgumentException();
+         }
+         this.field = field;
+         int coefficientsLength = coefficients.Length;
+         if (coefficientsLength > 1 && coefficients[0] == 0)
+         {
+            // Leading term must be non-zero for anything except the constant polynomial "0"
+            int firstNonZero = 1;
+            while (firstNonZero < coefficientsLength && coefficients[firstNonZero] == 0)
+            {
+               firstNonZero++;
+            }
+            if (firstNonZero == coefficientsLength)
+            {
+               this.coefficients = new int[]{0};
+            }
+            else
+            {
+               this.coefficients = new int[coefficientsLength - firstNonZero];
+               Array.Copy(coefficients,
+                          firstNonZero,
+                          this.coefficients,
+                          0,
+                          this.coefficients.Length);
+            }
+         }
+         else
+         {
+            this.coefficients = coefficients;
+         }
+      }
+
+      /// <summary>
+      /// Gets the coefficients.
+      /// </summary>
+      /// <value>The coefficients.</value>
+      internal int[] Coefficients
+      {
+         get { return coefficients; }
+      }
+
+      /// <summary>
+      /// degree of this polynomial
+      /// </summary>
+      internal int Degree
+      {
+         get
+         {
+            return coefficients.Length - 1;
+         }
+      }
+
+      /// <summary>
+      /// Gets a value indicating whether this instance is zero.
+      /// </summary>
+      /// <value>true if this polynomial is the monomial "0"
+      /// </value>
+      internal bool isZero
+      {
+         get { return coefficients[0] == 0; }
+      }
+
+      /// <summary>
+      /// coefficient of x^degree term in this polynomial
+      /// </summary>
+      /// <param name="degree">The degree.</param>
+      /// <returns>coefficient of x^degree term in this polynomial</returns>
+      internal int getCoefficient(int degree)
+      {
+         return coefficients[coefficients.Length - 1 - degree];
+      }
+
+      /// <summary>
+      /// evaluation of this polynomial at a given point
+      /// </summary>
+      /// <param name="a">A.</param>
+      /// <returns>evaluation of this polynomial at a given point</returns>
+      internal int evaluateAt(int a)
+      {
+         if (a == 0)
+         {
+            // Just return the x^0 coefficient
+            return getCoefficient(0);
+         }
+         int size = coefficients.Length;
+         int result = 0;
+         if (a == 1)
+         {
+            // Just the sum of the coefficients
+            foreach (var coefficient in coefficients)
+            {
+               result = field.add(result, coefficient);
+            }
+            return result;
+         }
+         result = coefficients[0];
+         for (int i = 1; i < size; i++)
+         {
+            result = field.add(field.multiply(a, result), coefficients[i]);
+         }
+         return result;
+      }
+
+      /// <summary>
+      /// Adds another Modulus
+      /// </summary>
+      /// <param name="other">Other.</param>
+      internal ModulusPoly add(ModulusPoly other)
+      {
+         if (!field.Equals(other.field))
+         {
+            throw new ArgumentException("ModulusPolys do not have same ModulusGF field");
+         }
+         if (isZero)
+         {
+            return other;
+         }
+         if (other.isZero)
+         {
+            return this;
+         }
+
+         int[] smallerCoefficients = this.coefficients;
+         int[] largerCoefficients = other.coefficients;
+         if (smallerCoefficients.Length > largerCoefficients.Length)
+         {
+            int[] temp = smallerCoefficients;
+            smallerCoefficients = largerCoefficients;
+            largerCoefficients = temp;
+         }
+         int[] sumDiff = new int[largerCoefficients.Length];
+         int lengthDiff = largerCoefficients.Length - smallerCoefficients.Length;
+         // Copy high-order terms only found in higher-degree polynomial's coefficients
+         Array.Copy(largerCoefficients, 0, sumDiff, 0, lengthDiff);
+
+         for (int i = lengthDiff; i < largerCoefficients.Length; i++)
+         {
+            sumDiff[i] = field.add(smallerCoefficients[i - lengthDiff], largerCoefficients[i]);
+         }
+
+         return new ModulusPoly(field, sumDiff);
+      }
+
+      /// <summary>
+      /// Subtract another Modulus
+      /// </summary>
+      /// <param name="other">Other.</param>
+      internal ModulusPoly subtract(ModulusPoly other)
+      {
+         if (!field.Equals(other.field))
+         {
+            throw new ArgumentException("ModulusPolys do not have same ModulusGF field");
+         }
+         if (other.isZero)
+         {
+            return this;
+         }
+         return add(other.getNegative());
+      }
+
+      /// <summary>
+      /// Multiply by another Modulus
+      /// </summary>
+      /// <param name="other">Other.</param>
+      internal ModulusPoly multiply(ModulusPoly other)
+      {
+         if (!field.Equals(other.field))
+         {
+            throw new ArgumentException("ModulusPolys do not have same ModulusGF field");
+         }
+         if (isZero || other.isZero)
+         {
+            return field.Zero;
+         }
+         int[] aCoefficients = this.coefficients;
+         int aLength = aCoefficients.Length;
+         int[] bCoefficients = other.coefficients;
+         int bLength = bCoefficients.Length;
+         int[] product = new int[aLength + bLength - 1];
+         for (int i = 0; i < aLength; i++)
+         {
+            int aCoeff = aCoefficients[i];
+            for (int j = 0; j < bLength; j++)
+            {
+               product[i + j] = field.add(product[i + j], field.multiply(aCoeff, bCoefficients[j]));
+            }
+         }
+         return new ModulusPoly(field, product);
+      }
+
+      /// <summary>
+      /// Returns a Negative version of this instance
+      /// </summary>
+      internal ModulusPoly getNegative()
+      {
+         int size = coefficients.Length;
+         int[] negativeCoefficients = new int[size];
+         for (int i = 0; i < size; i++)
+         {
+            negativeCoefficients[i] = field.subtract(0, coefficients[i]);
+         }
+         return new ModulusPoly(field, negativeCoefficients);
+      }
+
+      /// <summary>
+      /// Multiply by a Scalar.
+      /// </summary>
+      /// <param name="scalar">Scalar.</param>
+      internal ModulusPoly multiply(int scalar)
+      {
+         if (scalar == 0)
+         {
+            return field.Zero;
+         }
+         if (scalar == 1)
+         {
+            return this;
+         }
+         int size = coefficients.Length;
+         int[] product = new int[size];
+         for (int i = 0; i < size; i++)
+         {
+            product[i] = field.multiply(coefficients[i], scalar);
+         }
+         return new ModulusPoly(field, product);
+      }
+
+      /// <summary>
+      /// Multiplies by a Monomial
+      /// </summary>
+      /// <returns>The by monomial.</returns>
+      /// <param name="degree">Degree.</param>
+      /// <param name="coefficient">Coefficient.</param>
+      internal ModulusPoly multiplyByMonomial(int degree, int coefficient)
+      {
+         if (degree < 0)
+         {
+            throw new ArgumentException();
+         }
+         if (coefficient == 0)
+         {
+            return field.Zero;
+         }
+         int size = coefficients.Length;
+         int[] product = new int[size + degree];
+         for (int i = 0; i < size; i++)
+         {
+            product[i] = field.multiply(coefficients[i], coefficient);
+         }
+         return new ModulusPoly(field, product);
+      }
+
+      /// <summary>
+      /// Divide by another modulus
+      /// </summary>
+      /// <param name="other">Other.</param>
+      internal ModulusPoly[] divide(ModulusPoly other)
+      {
+         if (!field.Equals(other.field))
+         {
+            throw new ArgumentException("ModulusPolys do not have same ModulusGF field");
+         }
+         if (other.isZero)
+         {
+            throw new DivideByZeroException();
+         }
+
+         ModulusPoly quotient = field.Zero;
+         ModulusPoly remainder = this;
+
+         int denominatorLeadingTerm = other.getCoefficient(other.Degree);
+         int inverseDenominatorLeadingTerm = field.inverse(denominatorLeadingTerm);
+
+         while (remainder.Degree >= other.Degree && !remainder.isZero)
+         {
+            int degreeDifference = remainder.Degree - other.Degree;
+            int scale = field.multiply(remainder.getCoefficient(remainder.Degree), inverseDenominatorLeadingTerm);
+            ModulusPoly term = other.multiplyByMonomial(degreeDifference, scale);
+            ModulusPoly iterationQuotient = field.buildMonomial(degreeDifference, scale);
+            quotient = quotient.add(iterationQuotient);
+            remainder = remainder.subtract(term);
+         }
+
+         return new ModulusPoly[] { quotient, remainder };
+      }
+
+      /// <summary>
+      /// Returns a <see cref="System.String"/> that represents the current <see cref="ZXing.PDF417.Internal.EC.ModulusPoly"/>.
+      /// </summary>
+      /// <returns>A <see cref="System.String"/> that represents the current <see cref="ZXing.PDF417.Internal.EC.ModulusPoly"/>.</returns>
+      public override String ToString()
+      {
+         var result = new StringBuilder(8 * Degree);
+         for (int degree = Degree; degree >= 0; degree--)
+         {
+            int coefficient = getCoefficient(degree);
+            if (coefficient != 0)
+            {
+               if (coefficient < 0)
+               {
+                  result.Append(" - ");
+                  coefficient = -coefficient;
+               }
+               else
+               {
+                  if (result.Length > 0)
+                  {
+                     result.Append(" + ");
+                  }
+               }
+               if (degree == 0 || coefficient != 1)
+               {
+                  result.Append(coefficient);
+               }
+               if (degree != 0)
+               {
+                  if (degree == 1)
+                  {
+                     result.Append('x');
+                  }
+                  else
+                  {
+                     result.Append("x^");
+                     result.Append(degree);
+                  }
+               }
+            }
+         }
+         return result.ToString();
+      }
+   }
+}