2021SC@SDUSC

一、SymbolInfo

SymbolInfo是Data Matrix的符号信息表。
定义了如下信息表：

static final SymbolInfo[] PROD_SYMBOLS = {new SymbolInfo(false, 3, 5, 8, 8, 1),new SymbolInfo(false, 5, 7, 10, 10, 1),/*rect*/new SymbolInfo(true, 5, 7, 16, 6, 1),new SymbolInfo(false, 8, 10, 12, 12, 1),/*rect*/new SymbolInfo(true, 10, 11, 14, 6, 2),new SymbolInfo(false, 12, 12, 14, 14, 1),/*rect*/new SymbolInfo(true, 16, 14, 24, 10, 1),new SymbolInfo(false, 18, 14, 16, 16, 1),new SymbolInfo(false, 22, 18, 18, 18, 1),/*rect*/new SymbolInfo(true, 22, 18, 16, 10, 2),new SymbolInfo(false, 30, 20, 20, 20, 1),/*rect*/new SymbolInfo(true, 32, 24, 16, 14, 2),new SymbolInfo(false, 36, 24, 22, 22, 1),new SymbolInfo(false, 44, 28, 24, 24, 1),/*rect*/new SymbolInfo(true, 49, 28, 22, 14, 2),new SymbolInfo(false, 62, 36, 14, 14, 4),new SymbolInfo(false, 86, 42, 16, 16, 4),new SymbolInfo(false, 114, 48, 18, 18, 4),new SymbolInfo(false, 144, 56, 20, 20, 4),new SymbolInfo(false, 174, 68, 22, 22, 4),new SymbolInfo(false, 204, 84, 24, 24, 4, 102, 42),new SymbolInfo(false, 280, 112, 14, 14, 16, 140, 56),new SymbolInfo(false, 368, 144, 16, 16, 16, 92, 36),new SymbolInfo(false, 456, 192, 18, 18, 16, 114, 48),new SymbolInfo(false, 576, 224, 20, 20, 16, 144, 56),new SymbolInfo(false, 696, 272, 22, 22, 16, 174, 68),new SymbolInfo(false, 816, 336, 24, 24, 16, 136, 56),new SymbolInfo(false, 1050, 408, 18, 18, 36, 175, 68),new SymbolInfo(false, 1304, 496, 20, 20, 36, 163, 62),new DataMatrixSymbolInfo144(),};

并且有如下lookup方法：

public static SymbolInfo lookup(int dataCodewords,SymbolShapeHint shape,Dimension minSize,Dimension maxSize,boolean fail) {for (SymbolInfo symbol : symbols) {if (shape == SymbolShapeHint.FORCE_SQUARE && symbol.rectangular) {continue;}if (shape == SymbolShapeHint.FORCE_RECTANGLE && !symbol.rectangular) {continue;}if (minSize != null&& (symbol.getSymbolWidth() < minSize.getWidth()|| symbol.getSymbolHeight() < minSize.getHeight())) {continue;}if (maxSize != null&& (symbol.getSymbolWidth() > maxSize.getWidth()|| symbol.getSymbolHeight() > maxSize.getHeight())) {continue;}if (dataCodewords <= symbol.dataCapacity) {return symbol;}}if (fail) {throw new IllegalArgumentException("Can't find a symbol arrangement that matches the message. Data codewords: "+ dataCodewords);}return null;}

二、DefaultPlacement

DefaultPlacement符号字符放置程序。
重点是如下放置方法：首先，反复地先检查一个特殊的角落案例；
沿对角线向上扫掠，插入连续字符；
然后沿对角线向下扫掠，插入连续字符，直到扫描整个阵列；
最后，如果右下角未触及，则填充固定图案。

  public final void place() {int pos = 0;int row = 4;int col = 0;do {// 反复地先检查一个特殊的角落案例if ((row == numrows) && (col == 0)) {corner1(pos++);}if ((row == numrows - 2) && (col == 0) && ((numcols % 4) != 0)) {corner2(pos++);}if ((row == numrows - 2) && (col == 0) && (numcols % 8 == 4)) {corner3(pos++);}if ((row == numrows + 4) && (col == 2) && ((numcols % 8) == 0)) {corner4(pos++);}// 沿对角线向上扫掠，插入连续字符do {if ((row < numrows) && (col >= 0) && noBit(col, row)) {utah(row, col, pos++);}row -= 2;col += 2;} while (row >= 0 && (col < numcols));row++;col += 3;// 然后沿对角线向下扫掠，插入连续字符do {if ((row >= 0) && (col < numcols) && noBit(col, row)) {utah(row, col, pos++);}row += 2;col -= 2;} while ((row < numrows) && (col >= 0));row += 3;col++;// 直到扫描整个阵列} while ((row < numrows) || (col < numcols));// 最后，如果右下角未触及，则填充固定图案if (noBit(numcols - 1, numrows - 1)) {setBit(numcols - 1, numrows - 1, true);setBit(numcols - 2, numrows - 2, true);}}

三、ErrorCorrection

ECC200的纠错码。
DataMatrix ECC200采用Reed-Solomon纠错编码来为其提供纠错能力。RS编码的目标是计算出纠错码字，参考表来确定纠错码字的长度，考虑数据码字：66 67 68 69 70 142 129 56（“ABCDE12”通过ASCII编码），长度为8，则纠错码字长度为10，表示为RS(n,k)=RS(18, 8)。
设C(x)为数据码，
E(x)为纠错码字，G(x)为生成多项式，则：

由RS检验码生成多项式的一般形式为：

则有：

X分别取值，得到方程组：

然后用通过高斯消除法计算出E(x)={75 145 55 46 20 95 253 237 62 111}，最终生成18位码字{66 67 68 69 70 142 129 56 75 145 55 46 20 95 253 237 62 111}。

相关代码为：

  // 查找表要使用哪些因子来表示多少个纠错码字。private static final int[] FACTOR_SETS= {5, 7, 10, 11, 12, 14, 18, 20, 24, 28, 36, 42, 48, 56, 62, 68};// ECC 200的预计算多项式因子。private static final int[][] FACTORS = {{228, 48, 15, 111, 62},{23, 68, 144, 134, 240, 92, 254},{28, 24, 185, 166, 223, 248, 116, 255, 110, 61},{175, 138, 205, 12, 194, 168, 39, 245, 60, 97, 120},{41, 153, 158, 91, 61, 42, 142, 213, 97, 178, 100, 242},{156, 97, 192, 252, 95, 9, 157, 119, 138, 45, 18, 186, 83, 185},{83, 195, 100, 39, 188, 75, 66, 61, 241, 213, 109, 129, 94, 254, 225, 48, 90, 188},{15, 195, 244, 9, 233, 71, 168, 2, 188, 160, 153, 145, 253, 79, 108, 82, 27, 174, 186, 172},{52, 190, 88, 205, 109, 39, 176, 21, 155, 197, 251, 223, 155, 21, 5, 172,254, 124, 12, 181, 184, 96, 50, 193},{211, 231, 43, 97, 71, 96, 103, 174, 37, 151, 170, 53, 75, 34, 249, 121,17, 138, 110, 213, 141, 136, 120, 151, 233, 168, 93, 255},{245, 127, 242, 218, 130, 250, 162, 181, 102, 120, 84, 179, 220, 251, 80, 182,229, 18, 2, 4, 68, 33, 101, 137, 95, 119, 115, 44, 175, 184, 59, 25,225, 98, 81, 112},{77, 193, 137, 31, 19, 38, 22, 153, 247, 105, 122, 2, 245, 133, 242, 8,175, 95, 100, 9, 167, 105, 214, 111, 57, 121, 21, 1, 253, 57, 54, 101,248, 202, 69, 50, 150, 177, 226, 5, 9, 5},{245, 132, 172, 223, 96, 32, 117, 22, 238, 133, 238, 231, 205, 188, 237, 87,191, 106, 16, 147, 118, 23, 37, 90, 170, 205, 131, 88, 120, 100, 66, 138,186, 240, 82, 44, 176, 87, 187, 147, 160, 175, 69, 213, 92, 253, 225, 19},{175, 9, 223, 238, 12, 17, 220, 208, 100, 29, 175, 170, 230, 192, 215, 235,150, 159, 36, 223, 38, 200, 132, 54, 228, 146, 218, 234, 117, 203, 29, 232,144, 238, 22, 150, 201, 117, 62, 207, 164, 13, 137, 245, 127, 67, 247, 28,155, 43, 203, 107, 233, 53, 143, 46},{242, 93, 169, 50, 144, 210, 39, 118, 202, 188, 201, 189, 143, 108, 196, 37,185, 112, 134, 230, 245, 63, 197, 190, 250, 106, 185, 221, 175, 64, 114, 71,161, 44, 147, 6, 27, 218, 51, 63, 87, 10, 40, 130, 188, 17, 163, 31,176, 170, 4, 107, 232, 7, 94, 166, 224, 124, 86, 47, 11, 204},{220, 228, 173, 89, 251, 149, 159, 56, 89, 33, 147, 244, 154, 36, 73, 127,213, 136, 248, 180, 234, 197, 158, 177, 68, 122, 93, 213, 15, 160, 227, 236,66, 139, 153, 185, 202, 167, 179, 25, 220, 232, 96, 210, 231, 136, 223, 239,181, 241, 59, 52, 172, 25, 49, 232, 211, 189, 64, 54, 108, 153, 132, 63,96, 103, 82, 186}};

   // 为编码消息创建ECC200错误更正。// codewords  码字// symbolInfo 有关要编码的符号的信息// 返回交错纠错的码字。public static String encodeECC200(String codewords, SymbolInfo symbolInfo) {if (codewords.length() != symbolInfo.getDataCapacity()) {throw new IllegalArgumentException("The number of codewords does not match the selected symbol");}StringBuilder sb = new StringBuilder(symbolInfo.getDataCapacity() + symbolInfo.getErrorCodewords());sb.append(codewords);int blockCount = symbolInfo.getInterleavedBlockCount();if (blockCount == 1) {String ecc = createECCBlock(codewords, symbolInfo.getErrorCodewords());sb.append(ecc);} else {sb.setLength(sb.capacity());int[] dataSizes = new int[blockCount];int[] errorSizes = new int[blockCount];for (int i = 0; i < blockCount; i++) {dataSizes[i] = symbolInfo.getDataLengthForInterleavedBlock(i + 1);errorSizes[i] = symbolInfo.getErrorLengthForInterleavedBlock(i + 1);}for (int block = 0; block < blockCount; block++) {StringBuilder temp = new StringBuilder(dataSizes[block]);for (int d = block; d < symbolInfo.getDataCapacity(); d += blockCount) {temp.append(codewords.charAt(d));}String ecc = createECCBlock(temp.toString(), errorSizes[block]);int pos = 0;for (int e = block; e < errorSizes[block] * blockCount; e += blockCount) {sb.setCharAt(symbolInfo.getDataCapacity() + e, ecc.charAt(pos++));}}}return sb.toString();}

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2021SC@SDUSC Zxing开源代码（十）Data Matrix二维码（三）

目录

一、SymbolInfo

二、DefaultPlacement

三、ErrorCorrection

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