Split alphanumeric encoding from QRCodeGenerator, split encoding tables

QRCoder/QRCodeGenerator/AlignmentPatterns.cs

@@ -0,0 +1,62 @@
+using System.Collections.Generic;
+
+namespace QRCoder;
+
+public partial class QRCodeGenerator
+{
+    /// <summary>
+    /// This class contains the alignment patterns used in QR codes.
+    /// </summary>
+    private static class AlignmentPatterns
+    {
+        /// <summary>
+        /// A lookup table mapping QR code versions to their corresponding alignment patterns.
+        /// </summary>
+        private static readonly Dictionary<int, AlignmentPattern> _alignmentPatternTable = CreateAlignmentPatternTable();
+
+        /// <summary>
+        /// Retrieves the alignment pattern for a specific QR code version.
+        /// </summary>
+        public static AlignmentPattern FromVersion(int version) => _alignmentPatternTable[version];
+
+        /// <summary>
+        /// Creates a lookup table mapping QR code versions to their corresponding alignment patterns.
+        /// Alignment patterns are used in QR codes to help scanners accurately read the code at high speeds and when partially obscured.
+        /// This table provides the necessary patterns based on the QR code version which dictates the size and complexity of the QR code.
+        /// </summary>
+        /// <returns>A dictionary where keys are QR code version numbers and values are AlignmentPattern structures detailing the positions of alignment patterns for each version.</returns>
+        private static Dictionary<int, AlignmentPattern> CreateAlignmentPatternTable()
+        {
+            var alignmentPatternBaseValues = new int[] { 0, 0, 0, 0, 0, 0, 0, 6, 18, 0, 0, 0, 0, 0, 6, 22, 0, 0, 0, 0, 0, 6, 26, 0, 0, 0, 0, 0, 6, 30, 0, 0, 0, 0, 0, 6, 34, 0, 0, 0, 0, 0, 6, 22, 38, 0, 0, 0, 0, 6, 24, 42, 0, 0, 0, 0, 6, 26, 46, 0, 0, 0, 0, 6, 28, 50, 0, 0, 0, 0, 6, 30, 54, 0, 0, 0, 0, 6, 32, 58, 0, 0, 0, 0, 6, 34, 62, 0, 0, 0, 0, 6, 26, 46, 66, 0, 0, 0, 6, 26, 48, 70, 0, 0, 0, 6, 26, 50, 74, 0, 0, 0, 6, 30, 54, 78, 0, 0, 0, 6, 30, 56, 82, 0, 0, 0, 6, 30, 58, 86, 0, 0, 0, 6, 34, 62, 90, 0, 0, 0, 6, 28, 50, 72, 94, 0, 0, 6, 26, 50, 74, 98, 0, 0, 6, 30, 54, 78, 102, 0, 0, 6, 28, 54, 80, 106, 0, 0, 6, 32, 58, 84, 110, 0, 0, 6, 30, 58, 86, 114, 0, 0, 6, 34, 62, 90, 118, 0, 0, 6, 26, 50, 74, 98, 122, 0, 6, 30, 54, 78, 102, 126, 0, 6, 26, 52, 78, 104, 130, 0, 6, 30, 56, 82, 108, 134, 0, 6, 34, 60, 86, 112, 138, 0, 6, 30, 58, 86, 114, 142, 0, 6, 34, 62, 90, 118, 146, 0, 6, 30, 54, 78, 102, 126, 150, 6, 24, 50, 76, 102, 128, 154, 6, 28, 54, 80, 106, 132, 158, 6, 32, 58, 84, 110, 136, 162, 6, 26, 54, 82, 110, 138, 166, 6, 30, 58, 86, 114, 142, 170 };
+            var localAlignmentPatternTable = new Dictionary<int, AlignmentPattern>(40);
+
+            for (var i = 0; i < (7 * 40); i += 7)
+            {
+                var points = new List<Point>(50);
+                for (var x = 0; x < 7; x++)
+                {
+                    if (alignmentPatternBaseValues[i + x] != 0)
+                    {
+                        for (var y = 0; y < 7; y++)
+                        {
+                            if (alignmentPatternBaseValues[i + y] != 0)
+                            {
+                                var p = new Point(alignmentPatternBaseValues[i + x] - 2, alignmentPatternBaseValues[i + y] - 2);
+                                if (!points.Contains(p))
+                                    points.Add(p);
+                            }
+                        }
+                    }
+                }
+
+                var version = (i + 7) / 7;
+                localAlignmentPatternTable.Add(version, new AlignmentPattern()
+                {
+                    Version = version,
+                    PatternPositions = points
+                });
+            }
+            return localAlignmentPatternTable;
+        }
+    }
+}

QRCoder/QRCodeGenerator/AlphanumericEncoder.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace QRCoder;
+
+public partial class QRCodeGenerator
+{
+    /// <summary>
+    /// Encodes alphanumeric characters (<c>0–9</c>, <c>A–Z</c> (uppercase), space, <c>$</c>, <c>%</c>, <c>*</c>, <c>+</c>, <c>-</c>, period, <c>/</c>, colon) into a binary format suitable for QR codes.
+    /// </summary>
+    private static class AlphanumericEncoder
+    {
+        private static readonly char[] _alphanumEncTable = { ' ', '$', '%', '*', '+', '-', '.', '/', ':' };
+
+        /// <summary>
+        /// A dictionary mapping alphanumeric characters to their respective positions used in QR code encoding.
+        /// This includes digits 0-9, uppercase letters A-Z, and some special characters.
+        /// </summary>
+        private static readonly Dictionary<char, int> _alphanumEncDict = CreateAlphanumEncDict(_alphanumEncTable);
+
+        /// <summary>
+        /// Creates a dictionary mapping alphanumeric characters to their respective positions used in QR code encoding.
+        /// This includes digits 0-9, uppercase letters A-Z, and some special characters.
+        /// </summary>
+        /// <returns>A dictionary mapping each supported alphanumeric character to its corresponding value.</returns>
+        private static Dictionary<char, int> CreateAlphanumEncDict(char[] alphanumEncTable)
+        {
+            var localAlphanumEncDict = new Dictionary<char, int>(45);
+            // Add 0-9
+            for (char c = '0'; c <= '9'; c++)
+                localAlphanumEncDict.Add(c, c - '0');
+            // Add uppercase alphabetic characters.
+            for (char c = 'A'; c <= 'Z'; c++)
+                localAlphanumEncDict.Add(c, localAlphanumEncDict.Count);
+            // Add special characters from a predefined table.
+            for (int i = 0; i < _alphanumEncTable.Length; i++)
+                localAlphanumEncDict.Add(alphanumEncTable[i], localAlphanumEncDict.Count);
+            return localAlphanumEncDict;
+        }
+
+        /// <summary>
+        /// Checks if a character is present in the alphanumeric encoding table.
+        /// </summary>
+        public static bool CanEncode(char c) => IsInRange(c, 'A', 'Z') || Array.IndexOf(_alphanumEncTable, c) >= 0;
+
+        /// <summary>
+        /// Converts alphanumeric plain text into a binary format optimized for QR codes.
+        /// Alphanumeric encoding packs characters into 11-bit groups for each pair of characters,
+        /// and 6 bits for a single remaining character if the total count is odd.
+        /// </summary>
+        /// <param name="plainText">The alphanumeric text to be encoded, which should only contain characters valid in QR alphanumeric mode.</param>
+        /// <returns>A BitArray representing the binary data of the encoded alphanumeric text.</returns>
+        public static BitArray GetBitArray(string plainText)
+        {
+            // Calculate the length of the BitArray needed based on the number of character pairs.
+            var codeText = new BitArray((plainText.Length / 2) * 11 + (plainText.Length & 1) * 6);
+            var codeIndex = 0;
+            var index = 0;
+            var count = plainText.Length;
+
+            // Process each pair of characters.
+            while (count >= 2)
+            {
+                // Convert each pair of characters to a number by looking them up in the alphanumeric dictionary and calculating.
+                var dec = _alphanumEncDict[plainText[index++]] * 45 + _alphanumEncDict[plainText[index++]];
+                // Convert the number to binary and store it in the BitArray.
+                codeIndex = DecToBin(dec, 11, codeText, codeIndex);
+                count -= 2;
+            }
+
+            // Handle the last character if the length is odd.
+            if (count > 0)
+            {
+                DecToBin(_alphanumEncDict[plainText[index]], 6, codeText, codeIndex);
+            }
+
+            return codeText;
+        }
+    }
+}