zxing android 二维码扫描器实现源码

/* * Copyright 2009 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. */ package com.google.zxing.pdf417.decoder; import com.google.zxing.FormatException; import com.google.zxing.common.BitMatrix; /** * <p> * This class parses the BitMatrix image into codewords. * </p> * * @author SITA Lab (kevin.osullivan@sita.aero) */ final class BitMatrixParser { private static final int[] NO_ERRORS = new int[0]; private static final int MAX_ROW_DIFFERENCE = 6; private static final int MAX_ROWS = 90; //private static final int MAX_COLUMNS = 30; // Maximum Codewords (Data + Error) private static final int MAX_CW_CAPACITY = 929; private static final int MODULES_IN_SYMBOL = 17; private final BitMatrix bitMatrix; private int rows = 0; //private int columns = 0; private int leftColumnECData = 0; private int rightColumnECData = 0; private int eraseCount = 0; private int[] erasures; private int ecLevel = -1; BitMatrixParser(BitMatrix bitMatrix) { this.bitMatrix = bitMatrix; } /** * To ensure separability of rows, codewords of consecutive rows belong to * different subsets of all possible codewords. This routine scans the * symbols in the barcode. When it finds a number of consecutive rows which * are the same, it assumes that this is a row of codewords and processes * them into a codeword array. * * @return an array of codewords. */ int[] readCodewords() throws FormatException { int width = bitMatrix.getWidth(); int height = bitMatrix.getHeight(); erasures = new int[MAX_CW_CAPACITY]; // Get the number of pixels in a module across the X dimension //float moduleWidth = bitMatrix.getModuleWidth(); float moduleWidth = 1.0f; // Image has been sampled and reduced int[] rowCounters = new int[width]; int[] codewords = new int[MAX_CW_CAPACITY]; int next = 0; int matchingConsecutiveScans = 0; boolean rowInProgress = false; int rowNumber = 0; int rowHeight = 0; for (int i = 1; i < height; i++) { if (rowNumber >= MAX_ROWS) { // Something is wrong, since we have exceeded // the maximum rows in the specification. throw FormatException.getFormatInstance(); } int rowDifference = 0; // Scan a line of modules and check the // difference between this and the previous line for (int j = 0; j < width; j++) { // Accumulate differences between this line and the // previous line. if (bitMatrix.get(j, i) != bitMatrix.get(j, i - 1)) { rowDifference++; } } if (rowDifference <= moduleWidth * MAX_ROW_DIFFERENCE) { for (int j = 0; j < width; j++) { // Accumulate the black pixels on this line if (bitMatrix.get(j, i)) { rowCounters[j]++; } } // Increment the number of consecutive rows of pixels // that are more or less the same matchingConsecutiveScans++; // Height of a row is a multiple of the module size in pixels // Usually at least 3 times the module size if (matchingConsecutiveScans >= moduleWidth * 2) { // MGMG // We have some previous matches as well as a match here // Set processing a unique row. rowInProgress = true; } } else { if (rowInProgress) { // Process Row next = processRow(rowCounters, rowNumber, rowHeight, codewords, next); if (next == -1) { // Something is wrong, since we have exceeded // the maximum columns in the specification. throw FormatException.getFormatInstance(); } // Reinitialize the row counters. for (int j = 0; j < rowCounters.length; j++) { rowCounters[j] = 0; } rowNumber++; rowHeight = 0; } matchingConsecutiveScans = 0; rowInProgress = false; } rowHeight++; } // Check for a row that was in progress before we exited above. if (rowInProgress) { // Process Row if (rowNumber >= MAX_ROWS) { // Something is wrong, since we have exceeded // the maximum rows in the specification. throw FormatException.getFormatInstance(); } next = processRow(rowCounters, rowNumber, rowHeight, codewords, next); rowNumber++; rows = rowNumber; } erasures = trimArray(erasures, eraseCount); return trimArray(codewords, next); } /** * Trim the array to the required size. * * @param array the array * @param size the size to trim it to * @return the new trimmed array */ private static int[] trimArray(int[] array, int size) { if (size < 0) { throw new IllegalArgumentException(); } if (size == 0) { return NO_ERRORS; } int[] a = new int[size]; System.arraycopy(array, 0, a, 0, size); return a; } /** * Convert the symbols in the row to codewords. * Each PDF417 symbol character consists of four bar elements and four space * elements, each of which can be one to six modules wide. The four bar and * four space elements shall measure 17 modules in total. * * @param rowCounters an array containing the counts of black pixels for each column * in the row. * @param rowNumber the current row number of codewords. * @param rowHeight the height of this row in pixels. * @param codewords the codeword array to save codewords into. * @param next the next available index into the codewords array. * @return the next available index into the codeword array after processing * this row. */ int processRow(int[] rowCounters, int rowNumber, int rowHeight, int[] codewords, int next) throws FormatException { int width = bitMatrix.getWidth(); int columnNumber = 0; long symbol = 0; for (int i = 0; i < width; i += MODULES_IN_SYMBOL) { // This happens in real life and is almost surely a rare misdecode if (i + MODULES_IN_SYMBOL > rowCounters.length) { throw FormatException.getFormatInstance(); } for (int mask = MODULES_IN_SYMBOL - 1; mask >= 0; mask--) { if (rowCounters[i + (MODULES_IN_SYMBOL - 1 - mask)] >= rowHeight >>> 1) { symbol |= 1L << mask; } } if (columnNumber > 0) { int cw = getCodeword(symbol); if (cw < 0 && i < width - MODULES_IN_SYMBOL) { // Skip errors on the Right row indicator column if (eraseCount >= erasures.length) { throw FormatException.getFormatInstance(); } erasures[eraseCount] = next; next++; eraseCount++; } else { codewords[next++] = cw; } } else { // Left row indicator column int cw = getCodeword(symbol); if (ecLevel < 0) { switch (rowNumber % 3) { case 0: break; case 1: leftColumnECData = cw; break; case 2: break; } } } symbol = 0; //columns = columnNumber; columnNumber++; } if (col