mirror of
https://github.com/chillerlan/php-qrcode.git
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codemasher
332 lines
11 KiB
PHP
332 lines
11 KiB
PHP
<?php
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/**
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* Class Decoder
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*
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* @created 17.01.2021
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* @author ZXing Authors
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* @author Smiley <smiley@chillerlan.net>
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* @copyright 2021 Smiley
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* @license Apache-2.0
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*/
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namespace chillerlan\QRCode\Decoder;
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use InvalidArgumentException, RuntimeException, Throwable;
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use chillerlan\QRCode\Common\{BitBuffer, EccLevel, Mode, ReedSolomonDecoder, Version};
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use chillerlan\QRCode\Data\{AlphaNum, Byte, ECI, Kanji, Number};
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use chillerlan\QRCode\Detector\Detector;
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use function count, array_fill, mb_convert_encoding, mb_detect_encoding;
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/**
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* The main class which implements QR Code decoding -- as opposed to locating and extracting
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* the QR Code from an image.
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*
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* @author Sean Owen
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*/
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final class Decoder{
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# private const GB2312_SUBSET = 1;
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/**
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* Decodes a QR Code represented as a BitMatrix.
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* A 1 or "true" is taken to mean a black module.
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*
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* @param \chillerlan\QRCode\Decoder\LuminanceSourceInterface $source
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*
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* @return \chillerlan\QRCode\Decoder\DecoderResult text and bytes encoded within the QR Code
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* @throws \Throwable if the QR Code cannot be decoded
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*/
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public function decode(LuminanceSourceInterface $source):DecoderResult{
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$bitMatrix = (new Detector($source))->detect();
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try{
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// clone the BitMatrix to avoid errors in case we run into mirroring
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return $this->decodeMatrix(clone $bitMatrix);
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}
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catch(Throwable $e){
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try{
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/*
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* Prepare for a mirrored reading.
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*
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* Since we're here, this means we have successfully detected some kind
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* of version and format information when mirrored. This is a good sign,
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* that the QR code may be mirrored, and we should try once more with a
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* mirrored content.
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*/
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return $this->decodeMatrix($bitMatrix->setMirror(true)->mirror());
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}
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catch(Throwable $f){
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// Throw the exception from the original reading
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throw $e;
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}
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}
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}
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/**
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* @param \chillerlan\QRCode\Decoder\BitMatrix $bitMatrix
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*
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* @return \chillerlan\QRCode\Decoder\DecoderResult
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*/
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private function decodeMatrix(BitMatrix $bitMatrix):DecoderResult{
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// Read raw codewords
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$rawCodewords = $bitMatrix->readCodewords();
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$version = $bitMatrix->getVersion();
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$formatInfo = $bitMatrix->getFormatInfo();
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// technically this shouldn't happen as the respective read meathods would throw first
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if($version === null || $formatInfo === null){
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throw new RuntimeException('unable to read version or ecc level');
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}
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$eccLevel = $formatInfo->getErrorCorrectionLevel();
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// Separate into data blocks
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$dataBlocks = $this->getDataBlocks($rawCodewords, $version, $eccLevel);
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$resultBytes = [];
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$resultOffset = 0;
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// Error-correct and copy data blocks together into a stream of bytes
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foreach($dataBlocks as $dataBlock){
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[$numDataCodewords, $codewordBytes] = $dataBlock;
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$corrected = $this->correctErrors($codewordBytes, $numDataCodewords);
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for($i = 0; $i < $numDataCodewords; $i++){
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$resultBytes[$resultOffset++] = $corrected[$i];
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}
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}
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// Decode the contents of that stream of bytes
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return $this->decodeBitStream($resultBytes, $version, $eccLevel);
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}
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/**
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* When QR Codes use multiple data blocks, they are actually interleaved.
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* That is, the first byte of data block 1 to n is written, then the second bytes, and so on. This
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* method will separate the data into original blocks.
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*
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* @param array $rawCodewords bytes as read directly from the QR Code
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* @param \chillerlan\QRCode\Common\Version $version version of the QR Code
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* @param \chillerlan\QRCode\Common\EccLevel $eccLevel error-correction level of the QR Code
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*
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* @return array DataBlocks containing original bytes, "de-interleaved" from representation in the QR Code
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* @throws \InvalidArgumentException
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*/
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private function getDataBlocks(array $rawCodewords, Version $version, EccLevel $eccLevel):array{
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if(count($rawCodewords) !== $version->getTotalCodewords()){
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throw new InvalidArgumentException('$rawCodewords differ from total codewords for version');
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}
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// Figure out the number and size of data blocks used by this version and
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// error correction level
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[$numEccCodewords, $eccBlocks] = $version->getRSBlocks($eccLevel);
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// Now establish DataBlocks of the appropriate size and number of data codewords
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$result = [];//new DataBlock[$totalBlocks];
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$numResultBlocks = 0;
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foreach($eccBlocks as $blockData){
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[$numEccBlocks, $eccPerBlock] = $blockData;
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for($i = 0; $i < $numEccBlocks; $i++, $numResultBlocks++){
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$result[$numResultBlocks] = [$eccPerBlock, array_fill(0, $numEccCodewords + $eccPerBlock, 0)];
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}
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}
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// All blocks have the same amount of data, except that the last n
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// (where n may be 0) have 1 more byte. Figure out where these start.
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/** @phan-suppress-next-line PhanTypePossiblyInvalidDimOffset */
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$shorterBlocksTotalCodewords = count($result[0][1]);
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$longerBlocksStartAt = count($result) - 1;
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while($longerBlocksStartAt >= 0){
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$numCodewords = count($result[$longerBlocksStartAt][1]);
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if($numCodewords == $shorterBlocksTotalCodewords){
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break;
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}
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$longerBlocksStartAt--;
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}
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$longerBlocksStartAt++;
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$shorterBlocksNumDataCodewords = $shorterBlocksTotalCodewords - $numEccCodewords;
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// The last elements of result may be 1 element longer;
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// first fill out as many elements as all of them have
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$rawCodewordsOffset = 0;
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for($i = 0; $i < $shorterBlocksNumDataCodewords; $i++){
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for($j = 0; $j < $numResultBlocks; $j++){
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$result[$j][1][$i] = $rawCodewords[$rawCodewordsOffset++];
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}
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}
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// Fill out the last data block in the longer ones
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for($j = $longerBlocksStartAt; $j < $numResultBlocks; $j++){
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$result[$j][1][$shorterBlocksNumDataCodewords] = $rawCodewords[$rawCodewordsOffset++];
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}
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// Now add in error correction blocks
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/** @phan-suppress-next-line PhanTypePossiblyInvalidDimOffset */
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$max = count($result[0][1]);
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for($i = $shorterBlocksNumDataCodewords; $i < $max; $i++){
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for($j = 0; $j < $numResultBlocks; $j++){
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$iOffset = $j < $longerBlocksStartAt ? $i : $i + 1;
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$result[$j][1][$iOffset] = $rawCodewords[$rawCodewordsOffset++];
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}
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}
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return $result;
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}
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/**
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* Given data and error-correction codewords received, possibly corrupted by errors, attempts to
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* correct the errors in-place using Reed-Solomon error correction.
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*/
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private function correctErrors(array $codewordBytes, int $numDataCodewords):array{
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// First read into an array of ints
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$codewordsInts = [];
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foreach($codewordBytes as $i => $codewordByte){
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$codewordsInts[$i] = $codewordByte & 0xFF;
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}
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$decoded = (new ReedSolomonDecoder)->decode($codewordsInts, (count($codewordBytes) - $numDataCodewords));
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// Copy back into array of bytes -- only need to worry about the bytes that were data
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// We don't care about errors in the error-correction codewords
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for($i = 0; $i < $numDataCodewords; $i++){
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$codewordBytes[$i] = $decoded[$i];
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}
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return $codewordBytes;
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}
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/**
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* @throws \RuntimeException
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*/
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private function decodeBitStream(array $bytes, Version $version, EccLevel $ecLevel):DecoderResult{
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$bits = new BitBuffer($bytes);
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$symbolSequence = -1;
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$parityData = -1;
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$versionNumber = $version->getVersionNumber();
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$result = '';
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$eciCharset = null;
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# $fc1InEffect = false;
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// While still another segment to read...
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while($bits->available() >= 4){
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$datamode = $bits->read(4); // mode is encoded by 4 bits
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// OK, assume we're done. Really, a TERMINATOR mode should have been recorded here
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if($datamode === Mode::TERMINATOR){
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break;
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}
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if($datamode === Mode::ECI){
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// Count doesn't apply to ECI
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$eciCharset = ECI::parseValue($bits);
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}
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/** @noinspection PhpStatementHasEmptyBodyInspection */
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elseif($datamode === Mode::FNC1_FIRST || $datamode === Mode::FNC1_SECOND){
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// We do little with FNC1 except alter the parsed result a bit according to the spec
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# $fc1InEffect = true;
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}
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elseif($datamode === Mode::STRCTURED_APPEND){
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if($bits->available() < 16){
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throw new RuntimeException('structured append: not enough bits left');
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}
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// sequence number and parity is added later to the result metadata
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// Read next 8 bits (symbol sequence #) and 8 bits (parity data), then continue
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$symbolSequence = $bits->read(8);
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$parityData = $bits->read(8);
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}
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else{
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// First handle Hanzi mode which does not start with character count
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/* if($datamode === Mode::DATA_HANZI){
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//chinese mode contains a sub set indicator right after mode indicator
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$subset = $bits->read(4);
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$length = $bits->read(Mode::getLengthBitsForVersion($datamode, $versionNumber));
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if($subset === self::GB2312_SUBSET){
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$result .= $this->decodeHanziSegment($bits, $length);
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}
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}*/
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# else{
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// "Normal" QR code modes:
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if($datamode === Mode::NUMBER){
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$result .= Number::decodeSegment($bits, $versionNumber);
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}
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elseif($datamode === Mode::ALPHANUM){
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$str = AlphaNum::decodeSegment($bits, $versionNumber);
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// See section 6.4.8.1, 6.4.8.2
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/* if($fc1InEffect){
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$start = \strlen($str);
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// We need to massage the result a bit if in an FNC1 mode:
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for($i = $start; $i < $start; $i++){
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if($str[$i] === '%'){
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if($i < $start - 1 && $str[$i + 1] === '%'){
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// %% is rendered as %
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$str = \substr_replace($str, '', $i + 1, 1);//deleteCharAt(i + 1);
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}
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# else{
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// In alpha mode, % should be converted to FNC1 separator 0x1D @todo
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# $str = setCharAt($i, \chr(0x1D)); // ???
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# }
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}
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}
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}
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*/
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$result .= $str;
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}
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elseif($datamode === Mode::BYTE){
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$str = Byte::decodeSegment($bits, $versionNumber);
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if($eciCharset !== null){
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$encoding = $eciCharset->getName();
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if($encoding === null){
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// The spec isn't clear on this mode; see
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// section 6.4.5: t does not say which encoding to assuming
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// upon decoding. I have seen ISO-8859-1 used as well as
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// Shift_JIS -- without anything like an ECI designator to
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// give a hint.
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$encoding = mb_detect_encoding($str, ['ISO-8859-1', 'SJIS', 'UTF-8']);
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}
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$eciCharset = null;
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$str = mb_convert_encoding($str, $encoding);
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}
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$result .= $str;
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}
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elseif($datamode === Mode::KANJI){
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$result .= Kanji::decodeSegment($bits, $versionNumber);
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}
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else{
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throw new RuntimeException('invalid data mode');
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}
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# }
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}
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}
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return new DecoderResult([
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'rawBytes' => $bytes,
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'text' => $result,
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'version' => $version,
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'eccLevel' => $ecLevel,
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'structuredAppendParity' => $parityData,
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'structuredAppendSequence' => $symbolSequence
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]);
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}
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}
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