\Zxing\Qrcode\DecoderDecoder

<?php
/*
 * Copyright 2007 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\Qrcode\Decoder;

use Zxing\ChecksumException;
use Zxing\DecodeHintType;
use Zxing\FormatException;
use Zxing\Common\BitMatrix;
use Zxing\Common\DecoderResult;
use Zxing\Common\Reedsolomon\GenericGF;
use Zxing\Common\Reedsolomon\ReedSolomonDecoder;
use Zxing\Common\Reedsolomon\ReedSolomonException;

/**
 * <p>The main class which implements QR Code decoding -- as opposed to locating and extracting
 * the QR Code from an image.</p>
 *
 * @author Sean Owen
 */
final class Decoder
{

    private $rsDecoder;

    public function __construct()
    {
        $this->rsDecoder = new ReedSolomonDecoder(GenericGF::$QR_CODE_FIELD_256);
    }

    public function decode($variable, $hints = null)
    {
        if (is_array($variable)) {
            return $this->decodeImage($variable, $hints);
        } elseif ($variable instanceof BitMatrix) {
            return $this->decodeBits($variable, $hints);
        } elseif ($variable instanceof BitMatrixParser) {
            return $this->decodeParser($variable, $hints);
        }
        die('decode error Decoder.php');
    }

    /**
     * <p>Convenience method that can decode a QR Code represented as a 2D array of booleans.
     * "true" is taken to mean a black module.</p>
     *
     * @param array $image booleans representing white/black QR Code modules
     * @param       hints  decoding hints that should be used to influence decoding
     *
     * @return text and bytes encoded within the QR Code
     * @throws FormatException if the QR Code cannot be decoded
     * @throws ChecksumException if error correction fails
     */
    public function decodeImage($image, $hints = null)
    {
        $dimension = count($image);
        $bits      = new BitMatrix($dimension);
        for ($i = 0; $i < $dimension; $i++) {
            for ($j = 0; $j < $dimension; $j++) {
                if ($image[$i][$j]) {
                    $bits->set($j, $i);
                }
            }
        }

        return $this->decode($bits, $hints);
    }


    /**
     * <p>Decodes a QR Code represented as a {@link BitMatrix}. A 1 or "true" is taken to mean a black module.</p>
     *
     * @param BitMatrix $bits booleans representing white/black QR Code modules
     * @param           hints decoding hints that should be used to influence decoding
     *
     * @return text and bytes encoded within the QR Code
     * @throws FormatException if the QR Code cannot be decoded
     * @throws ChecksumException if error correction fails
     */
    public function decodeBits($bits, $hints = null)
    {

// Construct a parser and read version, error-correction level
        $parser = new BitMatrixParser($bits);
        $fe     = null;
        $ce     = null;
        try {
            return $this->decode($parser, $hints);
        } catch (FormatException $e) {
            $fe = $e;
        } catch (ChecksumException $e) {
            $ce = $e;
        }

        try {

            // Revert the bit matrix
            $parser->remask();

            // Will be attempting a mirrored reading of the version and format info.
            $parser->setMirror(true);

            // Preemptively read the version.
            $parser->readVersion();

            // Preemptively read the format information.
            $parser->readFormatInformation();

            /*
            * Since we're here, this means we have successfully detected some kind
            * of version and format information when mirrored. This is a good sign,
            * that the QR code may be mirrored, and we should try once more with a
            * mirrored content.
            */
            // Prepare for a mirrored reading.
            $parser->mirror();

            $result = $this->decode($parser, $hints);

            // Success! Notify the caller that the code was mirrored.
            $result->setOther(new QRCodeDecoderMetaData(true));

            return $result;

        } catch (FormatException $e) {// catch (FormatException | ChecksumException e) {
            // Throw the exception from the original reading
            if ($fe != null) {
                throw $fe;
            }
            if ($ce != null) {
                throw $ce;
            }
            throw $e;

        }
    }

    private function decodeParser($parser, $hints = null)
    {
        $version = $parser->readVersion();
        $ecLevel = $parser->readFormatInformation()->getErrorCorrectionLevel();

// Read codewords
        $codewords = $parser->readCodewords();
// Separate into data blocks
        $dataBlocks = DataBlock::getDataBlocks($codewords, $version, $ecLevel);

// Count total number of data bytes
        $totalBytes = 0;
        foreach ($dataBlocks as $dataBlock) {
            $totalBytes += $dataBlock->getNumDataCodewords();
        }
        $resultBytes  = fill_array(0, $totalBytes, 0);
        $resultOffset = 0;

// Error-correct and copy data blocks together into a stream of bytes
        foreach ($dataBlocks as $dataBlock) {
            $codewordBytes    = $dataBlock->getCodewords();
            $numDataCodewords = $dataBlock->getNumDataCodewords();
            $this->correctErrors($codewordBytes, $numDataCodewords);
            for ($i = 0; $i < $numDataCodewords; $i++) {
                $resultBytes[$resultOffset++] = $codewordBytes[$i];
            }
        }

// Decode the contents of that stream of bytes
        return DecodedBitStreamParser::decode($resultBytes, $version, $ecLevel, $hints);
    }

    /**
     * <p>Given data and error-correction codewords received, possibly corrupted by errors, attempts to
     * correct the errors in-place using Reed-Solomon error correction.</p>
     *
     * @param codewordBytes    data and error correction codewords
     * @param numDataCodewords number of codewords that are data bytes
     *
     * @throws ChecksumException if error correction fails
     */
    private function correctErrors(&$codewordBytes, $numDataCodewords)
    {
        $numCodewords = count($codewordBytes);
// First read into an array of ints
        $codewordsInts = fill_array(0, $numCodewords, 0);
        for ($i = 0; $i < $numCodewords; $i++) {
            $codewordsInts[$i] = $codewordBytes[$i] & 0xFF;
        }
        $numECCodewords = count($codewordBytes) - $numDataCodewords;
        try {
            $this->rsDecoder->decode($codewordsInts, $numECCodewords);
        } catch (ReedSolomonException $ignored) {
            throw ChecksumException::getChecksumInstance();
        }
// Copy back into array of bytes -- only need to worry about the bytes that were data
// We don't care about errors in the error-correction codewords
        for ($i = 0; $i < $numDataCodewords; $i++) {
            $codewordBytes[$i] = $codewordsInts[$i];
        }
    }
}