WebP.php

Go to the documentation of this file.

<?php
class WebPHandler extends BitmapHandler {
    const BROKEN_FILE = '0'; // value to store in img_metadata if error extracting metadata.
    const MINIMUM_CHUNK_HEADER_LENGTH = 18;
    const _MW_WEBP_VERSION = 1;

    const VP8X_ICC = 32;
    const VP8X_ALPHA = 16;
    const VP8X_EXIF = 8;
    const VP8X_XMP = 4;
    const VP8X_ANIM = 2;

    public function getMetadata( $image, $filename ) {
        $parsedWebPData = self::extractMetadata( $filename );
        if ( !$parsedWebPData ) {
            return self::BROKEN_FILE;
        }

        $parsedWebPData['metadata']['_MW_WEBP_VERSION'] = self::_MW_WEBP_VERSION;
        return serialize( $parsedWebPData );
    }

    public function getMetadataType( $image ) {
        return 'parsed-webp';
    }

    public function isMetadataValid( $image, $metadata ) {
        if ( $metadata === self::BROKEN_FILE ) {
                // Do not repetitivly regenerate metadata on broken file.
                return self::METADATA_GOOD;
        }

        MediaWiki\suppressWarnings();
        $data = unserialize( $metadata );
        MediaWiki\restoreWarnings();

        if ( !$data || !is_array( $data ) ) {
                wfDebug( __METHOD__ . " invalid WebP metadata\n" );

                return self::METADATA_BAD;
        }

        if ( !isset( $data['metadata']['_MW_WEBP_VERSION'] )
                || $data['metadata']['_MW_WEBP_VERSION'] != self::_MW_WEBP_VERSION
        ) {
                wfDebug( __METHOD__ . " old but compatible WebP metadata\n" );

                return self::METADATA_COMPATIBLE;
        }
        return self::METADATA_GOOD;
    }

    public static function extractMetadata( $filename ) {
        wfDebugLog( 'WebP', __METHOD__ . ": Extracting metadata from $filename\n" );

        $info = RiffExtractor::findChunksFromFile( $filename, 100 );
        if ( $info === false ) {
            wfDebugLog( 'WebP', __METHOD__ . ": Not a valid RIFF file\n" );
            return false;
        }

        if ( $info['fourCC'] != 'WEBP' ) {
            wfDebugLog( 'WebP', __METHOD__ . ': FourCC was not WEBP: ' .
                bin2hex( $info['fourCC'] ) . " \n" );
            return false;
        }

        $metadata = self::extractMetadataFromChunks( $info['chunks'], $filename );
        if ( !$metadata ) {
            wfDebugLog( 'WebP', __METHOD__ . ": No VP8 chunks found\n" );
            return false;
        }

        return $metadata;
    }

    public static function extractMetadataFromChunks( $chunks, $filename ) {
        $vp8Info = [];

        foreach ( $chunks as $chunk ) {
            if ( !in_array( $chunk['fourCC'], [ 'VP8 ', 'VP8L', 'VP8X' ] ) ) {
                // Not a chunk containing interesting metadata
                continue;
            }

            $chunkHeader = file_get_contents( $filename, false, null,
                $chunk['start'], self::MINIMUM_CHUNK_HEADER_LENGTH );
            wfDebugLog( 'WebP', __METHOD__ . ": {$chunk['fourCC']}\n" );

            switch ( $chunk['fourCC'] ) {
                case 'VP8 ':
                    return array_merge( $vp8Info,
                        self::decodeLossyChunkHeader( $chunkHeader ) );
                case 'VP8L':
                    return array_merge( $vp8Info,
                        self::decodeLosslessChunkHeader( $chunkHeader ) );
                case 'VP8X':
                    $vp8Info = array_merge( $vp8Info,
                        self::decodeExtendedChunkHeader( $chunkHeader ) );
                    // Continue looking for other chunks to improve the metadata
                    break;
            }
        }
        return $vp8Info;
    }

    protected static function decodeLossyChunkHeader( $header ) {
        // Bytes 0-3 are 'VP8 '
        // Bytes 4-7 are the VP8 stream size
        // Bytes 8-10 are the frame tag
        // Bytes 11-13 are 0x9D 0x01 0x2A called the sync code
        $syncCode = substr( $header, 11, 3 );
        if ( $syncCode != "\x9D\x01\x2A" ) {
            wfDebugLog( 'WebP', __METHOD__ . ': Invalid sync code: ' .
                bin2hex( $syncCode ) . "\n" );
            return [];
        }
        // Bytes 14-17 are image size
        $imageSize = unpack( 'v2', substr( $header, 14, 4 ) );
        // Image sizes are 14 bit, 2 MSB are scaling parameters which are ignored here
        return [
            'compression' => 'lossy',
            'width' => $imageSize[1] & 0x3FFF,
            'height' => $imageSize[2] & 0x3FFF
        ];
    }

    public static function decodeLosslessChunkHeader( $header ) {
        // Bytes 0-3 are 'VP8L'
        // Bytes 4-7 are chunk stream size
        // Byte 8 is 0x2F called the signature
        if ( $header{8} != "\x2F" ) {
            wfDebugLog( 'WebP', __METHOD__ . ': Invalid signature: ' .
                bin2hex( $header{8} ) . "\n" );
            return [];
        }
        // Bytes 9-12 contain the image size
        // Bits 0-13 are width-1; bits 15-27 are height-1
        $imageSize = unpack( 'C4', substr( $header, 9, 4 ) );
        return [
                'compression' => 'lossless',
                'width' => ( $imageSize[1] | ( ( $imageSize[2] & 0x3F ) << 8 ) ) + 1,
                'height' => ( ( ( $imageSize[2] & 0xC0 ) >> 6 ) |
                        ( $imageSize[3] << 2 ) | ( ( $imageSize[4] & 0x03 ) << 10 ) ) + 1
        ];
    }

    public static function decodeExtendedChunkHeader( $header ) {
        // Bytes 0-3 are 'VP8X'
        // Byte 4-7 are chunk length
        // Byte 8-11 are a flag bytes
        $flags = unpack( 'c', substr( $header, 8, 1 ) );

        // Byte 12-17 are image size (24 bits)
        $width = unpack( 'V', substr( $header, 12, 3 ) . "\x00" );
        $height = unpack( 'V', substr( $header, 15, 3 ) . "\x00" );

        return [
            'compression' => 'unknown',
            'animated' => ( $flags[1] & self::VP8X_ANIM ) == self::VP8X_ANIM,
            'transparency' => ( $flags[1] & self::VP8X_ALPHA ) == self::VP8X_ALPHA,
            'width' => ( $width[1] & 0xFFFFFF ) + 1,
            'height' => ( $height[1] & 0xFFFFFF ) + 1
        ];
    }

    public function getImageSize( $file, $path, $metadata = false ) {
        if ( $file === null ) {
            $metadata = self::getMetadata( $file, $path );
        }
        if ( $metadata === false && $file instanceof File ) {
            $metadata = $file->getMetadata();
        }

        MediaWiki\suppressWarnings();
        $metadata = unserialize( $metadata );
        MediaWiki\restoreWarnings();

        if ( $metadata == false ) {
            return false;
        }
        return [ $metadata['width'], $metadata['height'] ];
    }

    public function mustRender( $file ) {
        return true;
    }

    public function canRender( $file ) {
        if ( self::isAnimatedImage( $file ) ) {
            return false;
        }
        return true;
    }

    public function isAnimatedImage( $image ) {
        $ser = $image->getMetadata();
        if ( $ser ) {
            $metadata = unserialize( $ser );
            if ( isset( $metadata['animated'] ) && $metadata['animated'] === true ) {
                return true;
            }
        }

        return false;
    }

    public function canAnimateThumbnail( $file ) {
        return false;
    }

    public function getThumbType( $ext, $mime, $params = null ) {
        return [ 'png', 'image/png' ];
    }

    protected function getScalerType( $dstPath, $checkDstPath = true ) {
        return 'im';
    }
}