includes/media/WebPHandler.php
<?php
/**
* Handler for Google's WebP format <https://developers.google.com/speed/webp/>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Media
*/
/**
* Handler for Google's WebP format <https://developers.google.com/speed/webp/>
*
* @ingroup Media
*/
class WebPHandler extends BitmapHandler {
/**
* Value to store in img_metadata if there was an error extracting metadata
*/
private const BROKEN_FILE = '0';
/**
* Minimum chunk header size to be able to read all header types
*/
private const MINIMUM_CHUNK_HEADER_LENGTH = 18;
/**
* Version of the metadata stored in db records
*/
private const _MW_WEBP_VERSION = 1;
private const VP8X_ICC = 32;
private const VP8X_ALPHA = 16;
private const VP8X_EXIF = 8;
private const VP8X_XMP = 4;
private const VP8X_ANIM = 2;
public function getSizeAndMetadata( $state, $filename ) {
$parsedWebPData = self::extractMetadata( $filename );
if ( !$parsedWebPData ) {
return [ 'metadata' => [ '_error' => self::BROKEN_FILE ] ];
}
$parsedWebPData['metadata']['_MW_WEBP_VERSION'] = self::_MW_WEBP_VERSION;
$info = [
'width' => $parsedWebPData['width'],
'height' => $parsedWebPData['height'],
'metadata' => $parsedWebPData
];
return $info;
}
public function getMetadataType( $image ) {
return 'parsed-webp';
}
public function isFileMetadataValid( $image ) {
$data = $image->getMetadataArray();
if ( $data === [ '_error' => self::BROKEN_FILE ] ) {
// Do not repetitivly regenerate metadata on broken file.
return self::METADATA_GOOD;
}
if ( !$data || !isset( $data['_error'] ) ) {
wfDebug( __METHOD__ . " invalid WebP metadata" );
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" );
return self::METADATA_COMPATIBLE;
}
return self::METADATA_GOOD;
}
/**
* Extracts the image size and WebP type from a file
*
* @param string $filename
* @return array|false Header data array with entries 'compression', 'width' and 'height',
* where 'compression' can be 'lossy', 'lossless', 'animated' or 'unknown'. False if
* file is not a valid WebP file.
*/
public static function extractMetadata( $filename ) {
wfDebugLog( 'WebP', __METHOD__ . ": Extracting metadata from $filename" );
$info = RiffExtractor::findChunksFromFile( $filename, 100 );
if ( $info === false ) {
wfDebugLog( 'WebP', __METHOD__ . ": Not a valid RIFF file" );
return false;
}
if ( $info['fourCC'] !== 'WEBP' ) {
wfDebugLog( 'WebP', __METHOD__ . ': FourCC was not WEBP: ' .
bin2hex( $info['fourCC'] ) );
return false;
}
$metadata = self::extractMetadataFromChunks( $info['chunks'], $filename );
if ( !$metadata ) {
wfDebugLog( 'WebP', __METHOD__ . ": No VP8 chunks found" );
return false;
}
return $metadata;
}
/**
* Extracts the image size and WebP type from a file based on the chunk list
* @param array[] $chunks Chunks as extracted by RiffExtractor
* @param string $filename
* @return array Header data array with entries 'compression', 'width' and 'height', where
* 'compression' can be 'lossy', 'lossless', 'animated' or 'unknown'
*/
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']}" );
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;
}
/**
* Decodes a lossy chunk header
* @param string $header First few bytes of the header, expected to be at least 18 bytes long
* @return bool|array See WebPHandler::decodeHeader
*/
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 ) );
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
];
}
/**
* Decodes a lossless chunk header
* @param string $header First few bytes of the header, expected to be at least 13 bytes long
* @return bool|array See WebPHandler::decodeHeader
*/
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] ) );
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
];
}
/**
* Decodes an extended chunk header
* @param string $header First few bytes of the header, expected to be at least 18 bytes long
* @return bool|array See WebPHandler::decodeHeader
*/
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
];
}
/**
* @param File $file
* @return bool True, not all browsers support WebP
*/
public function mustRender( $file ) {
return true;
}
/**
* @param File $file
* @return bool False if we are unable to render this image
*/
public function canRender( $file ) {
if ( $this->isAnimatedImage( $file ) ) {
return false;
}
return true;
}
/**
* @param File $image
* @return bool
*/
public function isAnimatedImage( $image ) {
$metadata = $image->getMetadataArray();
if ( isset( $metadata['animated'] ) && $metadata['animated'] === true ) {
return true;
}
return false;
}
public function canAnimateThumbnail( $file ) {
return false;
}
/**
* Render files as PNG
*
* @param string $ext
* @param string $mime
* @param array|null $params
* @return array
*/
public function getThumbType( $ext, $mime, $params = null ) {
return [ 'png', 'image/png' ];
}
/**
* Must use "im" for XCF
*
* @param string|null $dstPath
* @param bool $checkDstPath
* @return string
*/
protected function getScalerType( $dstPath, $checkDstPath = true ) {
return 'im';
}
}