Merge "Make update.php file executable"

[mediawiki.git] / includes / media / Bitmap.php

<?php
/**
 * Generic handler for bitmap images.
 *
 * 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
 */

/**
 * Generic handler for bitmap images
 *
 * @ingroup Media
 */
class BitmapHandler extends ImageHandler {
        /**
         * @param File $image
         * @param array $params Transform parameters. Entries with the keys 'width'
         * and 'height' are the respective screen width and height, while the keys
         * 'physicalWidth' and 'physicalHeight' indicate the thumbnail dimensions.
         * @return bool
         */
        function normaliseParams( $image, &$params ) {
                if ( !parent::normaliseParams( $image, $params ) ) {
                        return false;
                }

                # Obtain the source, pre-rotation dimensions
                $srcWidth = $image->getWidth( $params['page'] );
                $srcHeight = $image->getHeight( $params['page'] );

                # Don't make an image bigger than the source
                if ( $params['physicalWidth'] >= $srcWidth ) {
                        $params['physicalWidth'] = $srcWidth;
                        $params['physicalHeight'] = $srcHeight;

                        # Skip scaling limit checks if no scaling is required
                        # due to requested size being bigger than source.
                        if ( !$image->mustRender() ) {
                                return true;
                        }
                }

                # Check if the file is smaller than the maximum image area for thumbnailing
                $checkImageAreaHookResult = null;
                wfRunHooks(
                        'BitmapHandlerCheckImageArea',
                        array( $image, &$params, &$checkImageAreaHookResult )
                );

                if ( is_null( $checkImageAreaHookResult ) ) {
                        global $wgMaxImageArea;

                        if ( $srcWidth * $srcHeight > $wgMaxImageArea
                                && !( $image->getMimeType() == 'image/jpeg'
                                        && self::getScalerType( false, false ) == 'im' )
                        ) {
                                # Only ImageMagick can efficiently downsize jpg images without loading
                                # the entire file in memory
                                return false;
                        }
                } else {
                        return $checkImageAreaHookResult;
                }

                return true;
        }

        /**
         * Extracts the width/height if the image will be scaled before rotating
         *
         * This will match the physical size/aspect ratio of the original image
         * prior to application of the rotation -- so for a portrait image that's
         * stored as raw landscape with 90-degress rotation, the resulting size
         * will be wider than it is tall.
         *
         * @param array $params Parameters as returned by normaliseParams
         * @param int $rotation The rotation angle that will be applied
         * @return array ($width, $height) array
         */
        public function extractPreRotationDimensions( $params, $rotation ) {
                if ( $rotation == 90 || $rotation == 270 ) {
                        # We'll resize before rotation, so swap the dimensions again
                        $width = $params['physicalHeight'];
                        $height = $params['physicalWidth'];
                } else {
                        $width = $params['physicalWidth'];
                        $height = $params['physicalHeight'];
                }

                return array( $width, $height );
        }

        /**
         * @param File $image
         * @param string $dstPath
         * @param string $dstUrl
         * @param array $params
         * @param int $flags
         * @return MediaTransformError|ThumbnailImage|TransformParameterError
         */
        function doTransform( $image, $dstPath, $dstUrl, $params, $flags = 0 ) {
                if ( !$this->normaliseParams( $image, $params ) ) {
                        return new TransformParameterError( $params );
                }
                # Create a parameter array to pass to the scaler
                $scalerParams = array(
                        # The size to which the image will be resized
                        'physicalWidth' => $params['physicalWidth'],
                        'physicalHeight' => $params['physicalHeight'],
                        'physicalDimensions' => "{$params['physicalWidth']}x{$params['physicalHeight']}",
                        # The size of the image on the page
                        'clientWidth' => $params['width'],
                        'clientHeight' => $params['height'],
                        # Comment as will be added to the Exif of the thumbnail
                        'comment' => isset( $params['descriptionUrl'] )
                                ? "File source: {$params['descriptionUrl']}"
                                : '',
                        # Properties of the original image
                        'srcWidth' => $image->getWidth(),
                        'srcHeight' => $image->getHeight(),
                        'mimeType' => $image->getMimeType(),
                        'dstPath' => $dstPath,
                        'dstUrl' => $dstUrl,
                );

                if ( isset( $params['quality'] ) && $params['quality'] === 'low' ) {
                        $scalerParams['quality'] = 30;
                }

                # Determine scaler type
                $scaler = self::getScalerType( $dstPath );

                wfDebug( __METHOD__ . ": creating {$scalerParams['physicalDimensions']} " .
                        "thumbnail at $dstPath using scaler $scaler\n" );

                if ( !$image->mustRender() &&
                        $scalerParams['physicalWidth'] == $scalerParams['srcWidth']
                        && $scalerParams['physicalHeight'] == $scalerParams['srcHeight']
                        && !isset( $scalerParams['quality'] )
                ) {

                        # normaliseParams (or the user) wants us to return the unscaled image
                        wfDebug( __METHOD__ . ": returning unscaled image\n" );

                        return $this->getClientScalingThumbnailImage( $image, $scalerParams );
                }

                if ( $scaler == 'client' ) {
                        # Client-side image scaling, use the source URL
                        # Using the destination URL in a TRANSFORM_LATER request would be incorrect
                        return $this->getClientScalingThumbnailImage( $image, $scalerParams );
                }

                if ( $flags & self::TRANSFORM_LATER ) {
                        wfDebug( __METHOD__ . ": Transforming later per flags.\n" );
                        $newParams = array(
                                'width' => $scalerParams['clientWidth'],
                                'height' => $scalerParams['clientHeight']
                        );
                        if ( isset( $params['quality'] ) ) {
                                $newParams['quality'] = $params['quality'];
                        }
                        return new ThumbnailImage( $image, $dstUrl, false, $newParams );
                }

                # Try to make a target path for the thumbnail
                if ( !wfMkdirParents( dirname( $dstPath ), null, __METHOD__ ) ) {
                        wfDebug( __METHOD__ . ": Unable to create thumbnail destination " .
                                "directory, falling back to client scaling\n" );

                        return $this->getClientScalingThumbnailImage( $image, $scalerParams );
                }

                # Transform functions and binaries need a FS source file
                $scalerParams['srcPath'] = $image->getLocalRefPath();
                if ( $scalerParams['srcPath'] === false ) { // Failed to get local copy
                        wfDebugLog( 'thumbnail',
                                sprintf( 'Thumbnail failed on %s: could not get local copy of "%s"',
                                        wfHostname(), $image->getName() ) );

                        return new MediaTransformError( 'thumbnail_error',
                                $scalerParams['clientWidth'], $scalerParams['clientHeight'],
                                wfMessage( 'filemissing' )->text()
                        );
                }

                # Try a hook
                $mto = null;
                wfRunHooks( 'BitmapHandlerTransform', array( $this, $image, &$scalerParams, &$mto ) );
                if ( !is_null( $mto ) ) {
                        wfDebug( __METHOD__ . ": Hook to BitmapHandlerTransform created an mto\n" );
                        $scaler = 'hookaborted';
                }

                switch ( $scaler ) {
                        case 'hookaborted':
                                # Handled by the hook above
                                /** @var MediaTransformOutput $mto */
                                $err = $mto->isError() ? $mto : false;
                                break;
                        case 'im':
                                $err = $this->transformImageMagick( $image, $scalerParams );
                                break;
                        case 'custom':
                                $err = $this->transformCustom( $image, $scalerParams );
                                break;
                        case 'imext':
                                $err = $this->transformImageMagickExt( $image, $scalerParams );
                                break;
                        case 'gd':
                        default:
                                $err = $this->transformGd( $image, $scalerParams );
                                break;
                }

                # Remove the file if a zero-byte thumbnail was created, or if there was an error
                $removed = $this->removeBadFile( $dstPath, (bool)$err );
                if ( $err ) {
                        # transform returned MediaTransforError
                        return $err;
                } elseif ( $removed ) {
                        # Thumbnail was zero-byte and had to be removed
                        return new MediaTransformError( 'thumbnail_error',
                                $scalerParams['clientWidth'], $scalerParams['clientHeight'],
                                wfMessage( 'unknown-error' )->text()
                        );
                } elseif ( $mto ) {
                        return $mto;
                } else {
                        $newParams = array(
                                'width' => $scalerParams['clientWidth'],
                                'height' => $scalerParams['clientHeight']
                        );
                        if ( isset( $params['quality'] ) ) {
                                $newParams['quality'] = $params['quality'];
                        }
                        return new ThumbnailImage( $image, $dstUrl, $dstPath, $newParams );
                }
        }

        /**
         * Returns which scaler type should be used. Creates parent directories
         * for $dstPath and returns 'client' on error
         *
         * @param string $dstPath
         * @param bool $checkDstPath
         * @return string One of client, im, custom, gd, imext
         */
        protected static function getScalerType( $dstPath, $checkDstPath = true ) {
                global $wgUseImageResize, $wgUseImageMagick, $wgCustomConvertCommand;

                if ( !$dstPath && $checkDstPath ) {
                        # No output path available, client side scaling only
                        $scaler = 'client';
                } elseif ( !$wgUseImageResize ) {
                        $scaler = 'client';
                } elseif ( $wgUseImageMagick ) {
                        $scaler = 'im';
                } elseif ( $wgCustomConvertCommand ) {
                        $scaler = 'custom';
                } elseif ( function_exists( 'imagecreatetruecolor' ) ) {
                        $scaler = 'gd';
                } elseif ( class_exists( 'Imagick' ) ) {
                        $scaler = 'imext';
                } else {
                        $scaler = 'client';
                }

                return $scaler;
        }

        /**
         * Get a ThumbnailImage that respresents an image that will be scaled
         * client side
         *
         * @param File $image File associated with this thumbnail
         * @param array $scalerParams Array with scaler params
         * @return ThumbnailImage
         *
         * @todo FIXME: No rotation support
         */
        protected function getClientScalingThumbnailImage( $image, $scalerParams ) {
                $params = array(
                        'width' => $scalerParams['clientWidth'],
                        'height' => $scalerParams['clientHeight']
                );

                return new ThumbnailImage( $image, $image->getURL(), null, $params );
        }

        /**
         * Transform an image using ImageMagick
         *
         * @param File $image File associated with this thumbnail
         * @param array $params Array with scaler params
         *
         * @return MediaTransformError Error object if error occurred, false (=no error) otherwise
         */
        protected function transformImageMagick( $image, $params ) {
                # use ImageMagick
                global $wgSharpenReductionThreshold, $wgSharpenParameter, $wgMaxAnimatedGifArea,
                        $wgImageMagickTempDir, $wgImageMagickConvertCommand;

                $quality = array();
                $sharpen = array();
                $scene = false;
                $animation_pre = array();
                $animation_post = array();
                $decoderHint = array();
                if ( $params['mimeType'] == 'image/jpeg' ) {
                        $qualityVal = isset( $params['quality'] ) ? (string) $params['quality'] : null;
                        $quality = array( '-quality', $qualityVal ?: '80' ); // 80%
                        # Sharpening, see bug 6193
                        if ( ( $params['physicalWidth'] + $params['physicalHeight'] )
                                / ( $params['srcWidth'] + $params['srcHeight'] )
                                < $wgSharpenReductionThreshold
                        ) {
                                $sharpen = array( '-sharpen', $wgSharpenParameter );
                        }
                        if ( version_compare( $this->getMagickVersion(), "6.5.6" ) >= 0 ) {
                                // JPEG decoder hint to reduce memory, available since IM 6.5.6-2
                                $decoderHint = array( '-define', "jpeg:size={$params['physicalDimensions']}" );
                        }
                } elseif ( $params['mimeType'] == 'image/png' ) {
                        $quality = array( '-quality', '95' ); // zlib 9, adaptive filtering

                } elseif ( $params['mimeType'] == 'image/gif' ) {
                        if ( $this->getImageArea( $image ) > $wgMaxAnimatedGifArea ) {
                                // Extract initial frame only; we're so big it'll
                                // be a total drag. :P
                                $scene = 0;
                        } elseif ( $this->isAnimatedImage( $image ) ) {
                                // Coalesce is needed to scale animated GIFs properly (bug 1017).
                                $animation_pre = array( '-coalesce' );
                                // We optimize the output, but -optimize is broken,
                                // use optimizeTransparency instead (bug 11822)
                                if ( version_compare( $this->getMagickVersion(), "6.3.5" ) >= 0 ) {
                                        $animation_post = array( '-fuzz', '5%', '-layers', 'optimizeTransparency' );
                                }
                        }
                } elseif ( $params['mimeType'] == 'image/x-xcf' ) {
                        $animation_post = array( '-layers', 'merge' );
                }

                // Use one thread only, to avoid deadlock bugs on OOM
                $env = array( 'OMP_NUM_THREADS' => 1 );
                if ( strval( $wgImageMagickTempDir ) !== '' ) {
                        $env['MAGICK_TMPDIR'] = $wgImageMagickTempDir;
                }

                $rotation = $this->getRotation( $image );
                list( $width, $height ) = $this->extractPreRotationDimensions( $params, $rotation );

                $cmd = call_user_func_array( 'wfEscapeShellArg', array_merge(
                        array( $wgImageMagickConvertCommand ),
                        $quality,
                        // Specify white background color, will be used for transparent images
                        // in Internet Explorer/Windows instead of default black.
                        array( '-background', 'white' ),
                        $decoderHint,
                        array( $this->escapeMagickInput( $params['srcPath'], $scene ) ),
                        $animation_pre,
                        // For the -thumbnail option a "!" is needed to force exact size,
                        // or ImageMagick may decide your ratio is wrong and slice off
                        // a pixel.
                        array( '-thumbnail', "{$width}x{$height}!" ),
                        // Add the source url as a comment to the thumb, but don't add the flag if there's no comment
                        ( $params['comment'] !== ''
                                ? array( '-set', 'comment', $this->escapeMagickProperty( $params['comment'] ) )
                                : array() ),
                        array( '-depth', 8 ),
                        $sharpen,
                        array( '-rotate', "-$rotation" ),
                        $animation_post,
                        array( $this->escapeMagickOutput( $params['dstPath'] ) ) ) );

                wfDebug( __METHOD__ . ": running ImageMagick: $cmd\n" );
                wfProfileIn( 'convert' );
                $retval = 0;
                $err = wfShellExecWithStderr( $cmd, $retval, $env );
                wfProfileOut( 'convert' );

                if ( $retval !== 0 ) {
                        $this->logErrorForExternalProcess( $retval, $err, $cmd );

                        return $this->getMediaTransformError( $params, "$err\nError code: $retval" );
                }

                return false; # No error
        }

        /**
         * Transform an image using the Imagick PHP extension
         *
         * @param File $image File associated with this thumbnail
         * @param array $params Array with scaler params
         *
         * @return MediaTransformError Error object if error occurred, false (=no error) otherwise
         */
        protected function transformImageMagickExt( $image, $params ) {
                global $wgSharpenReductionThreshold, $wgSharpenParameter, $wgMaxAnimatedGifArea;

                try {
                        $im = new Imagick();
                        $im->readImage( $params['srcPath'] );

                        if ( $params['mimeType'] == 'image/jpeg' ) {
                                // Sharpening, see bug 6193
                                if ( ( $params['physicalWidth'] + $params['physicalHeight'] )
                                        / ( $params['srcWidth'] + $params['srcHeight'] )
                                        < $wgSharpenReductionThreshold
                                ) {
                                        // Hack, since $wgSharpenParamater is written specifically for the command line convert
                                        list( $radius, $sigma ) = explode( 'x', $wgSharpenParameter );
                                        $im->sharpenImage( $radius, $sigma );
                                }
                                $qualityVal = isset( $params['quality'] ) ? (string) $params['quality'] : null;
                                $im->setCompressionQuality( $qualityVal ?: 80 );
                        } elseif ( $params['mimeType'] == 'image/png' ) {
                                $im->setCompressionQuality( 95 );
                        } elseif ( $params['mimeType'] == 'image/gif' ) {
                                if ( $this->getImageArea( $image ) > $wgMaxAnimatedGifArea ) {
                                        // Extract initial frame only; we're so big it'll
                                        // be a total drag. :P
                                        $im->setImageScene( 0 );
                                } elseif ( $this->isAnimatedImage( $image ) ) {
                                        // Coalesce is needed to scale animated GIFs properly (bug 1017).
                                        $im = $im->coalesceImages();
                                }
                        }

                        $rotation = $this->getRotation( $image );
                        list( $width, $height ) = $this->extractPreRotationDimensions( $params, $rotation );

                        $im->setImageBackgroundColor( new ImagickPixel( 'white' ) );

                        // Call Imagick::thumbnailImage on each frame
                        foreach ( $im as $i => $frame ) {
                                if ( !$frame->thumbnailImage( $width, $height, /* fit */ false ) ) {
                                        return $this->getMediaTransformError( $params, "Error scaling frame $i" );
                                }
                        }
                        $im->setImageDepth( 8 );

                        if ( $rotation ) {
                                if ( !$im->rotateImage( new ImagickPixel( 'white' ), 360 - $rotation ) ) {
                                        return $this->getMediaTransformError( $params, "Error rotating $rotation degrees" );
                                }
                        }

                        if ( $this->isAnimatedImage( $image ) ) {
                                wfDebug( __METHOD__ . ": Writing animated thumbnail\n" );
                                // This is broken somehow... can't find out how to fix it
                                $result = $im->writeImages( $params['dstPath'], true );
                        } else {
                                $result = $im->writeImage( $params['dstPath'] );
                        }
                        if ( !$result ) {
                                return $this->getMediaTransformError( $params,
                                        "Unable to write thumbnail to {$params['dstPath']}" );
                        }
                } catch ( ImagickException $e ) {
                        return $this->getMediaTransformError( $params, $e->getMessage() );
                }

                return false;
        }

        /**
         * Transform an image using a custom command
         *
         * @param File $image File associated with this thumbnail
         * @param array $params Array with scaler params
         *
         * @return MediaTransformError Error object if error occurred, false (=no error) otherwise
         */
        protected function transformCustom( $image, $params ) {
                # Use a custom convert command
                global $wgCustomConvertCommand;

                # Variables: %s %d %w %h
                $src = wfEscapeShellArg( $params['srcPath'] );
                $dst = wfEscapeShellArg( $params['dstPath'] );
                $cmd = $wgCustomConvertCommand;
                $cmd = str_replace( '%s', $src, str_replace( '%d', $dst, $cmd ) ); # Filenames
                $cmd = str_replace( '%h', wfEscapeShellArg( $params['physicalHeight'] ),
                        str_replace( '%w', wfEscapeShellArg( $params['physicalWidth'] ), $cmd ) ); # Size
                wfDebug( __METHOD__ . ": Running custom convert command $cmd\n" );
                wfProfileIn( 'convert' );
                $retval = 0;
                $err = wfShellExecWithStderr( $cmd, $retval );
                wfProfileOut( 'convert' );

                if ( $retval !== 0 ) {
                        $this->logErrorForExternalProcess( $retval, $err, $cmd );

                        return $this->getMediaTransformError( $params, $err );
                }

                return false; # No error
        }

        /**
         * Get a MediaTransformError with error 'thumbnail_error'
         *
         * @param array $params Parameter array as passed to the transform* functions
         * @param string $errMsg Error message
         * @return MediaTransformError
         */
        public function getMediaTransformError( $params, $errMsg ) {
                return new MediaTransformError( 'thumbnail_error', $params['clientWidth'],
                        $params['clientHeight'], $errMsg );
        }

        /**
         * Transform an image using the built in GD library
         *
         * @param File $image File associated with this thumbnail
         * @param array $params Array with scaler params
         *
         * @return MediaTransformError Error object if error occurred, false (=no error) otherwise
         */
        protected function transformGd( $image, $params ) {
                # Use PHP's builtin GD library functions.
                #
                # First find out what kind of file this is, and select the correct
                # input routine for this.

                $typemap = array(
                        'image/gif' => array( 'imagecreatefromgif', 'palette', false, 'imagegif' ),
                        'image/jpeg' => array( 'imagecreatefromjpeg', 'truecolor', true,
                                array( __CLASS__, 'imageJpegWrapper' ) ),
                        'image/png' => array( 'imagecreatefrompng', 'bits', false, 'imagepng' ),
                        'image/vnd.wap.wbmp' => array( 'imagecreatefromwbmp', 'palette', false, 'imagewbmp' ),
                        'image/xbm' => array( 'imagecreatefromxbm', 'palette', false, 'imagexbm' ),
                );

                if ( !isset( $typemap[$params['mimeType']] ) ) {
                        $err = 'Image type not supported';
                        wfDebug( "$err\n" );
                        $errMsg = wfMessage( 'thumbnail_image-type' )->text();

                        return $this->getMediaTransformError( $params, $errMsg );
                }
                list( $loader, $colorStyle, $useQuality, $saveType ) = $typemap[$params['mimeType']];

                if ( !function_exists( $loader ) ) {
                        $err = "Incomplete GD library configuration: missing function $loader";
                        wfDebug( "$err\n" );
                        $errMsg = wfMessage( 'thumbnail_gd-library', $loader )->text();

                        return $this->getMediaTransformError( $params, $errMsg );
                }

                if ( !file_exists( $params['srcPath'] ) ) {
                        $err = "File seems to be missing: {$params['srcPath']}";
                        wfDebug( "$err\n" );
                        $errMsg = wfMessage( 'thumbnail_image-missing', $params['srcPath'] )->text();

                        return $this->getMediaTransformError( $params, $errMsg );
                }

                $src_image = call_user_func( $loader, $params['srcPath'] );

                $rotation = function_exists( 'imagerotate' ) ? $this->getRotation( $image ) : 0;
                list( $width, $height ) = $this->extractPreRotationDimensions( $params, $rotation );
                $dst_image = imagecreatetruecolor( $width, $height );

                // Initialise the destination image to transparent instead of
                // the default solid black, to support PNG and GIF transparency nicely
                $background = imagecolorallocate( $dst_image, 0, 0, 0 );
                imagecolortransparent( $dst_image, $background );
                imagealphablending( $dst_image, false );

                if ( $colorStyle == 'palette' ) {
                        // Don't resample for paletted GIF images.
                        // It may just uglify them, and completely breaks transparency.
                        imagecopyresized( $dst_image, $src_image,
                                0, 0, 0, 0,
                                $width, $height,
                                imagesx( $src_image ), imagesy( $src_image ) );
                } else {
                        imagecopyresampled( $dst_image, $src_image,
                                0, 0, 0, 0,
                                $width, $height,
                                imagesx( $src_image ), imagesy( $src_image ) );
                }

                if ( $rotation % 360 != 0 && $rotation % 90 == 0 ) {
                        $rot_image = imagerotate( $dst_image, $rotation, 0 );
                        imagedestroy( $dst_image );
                        $dst_image = $rot_image;
                }

                imagesavealpha( $dst_image, true );

                $funcParams = array( $dst_image, $params['dstPath'] );
                if ( $useQuality && isset( $params['quality'] ) ) {
                        $funcParams[] = $params['quality'];
                }
                call_user_func_array( $saveType, $funcParams );

                imagedestroy( $dst_image );
                imagedestroy( $src_image );

                return false; # No error
        }

        /**
         * Escape a string for ImageMagick's property input (e.g. -set -comment)
         * See InterpretImageProperties() in magick/property.c
         * @param string $s
         * @return string
         */
        function escapeMagickProperty( $s ) {
                // Double the backslashes
                $s = str_replace( '\\', '\\\\', $s );
                // Double the percents
                $s = str_replace( '%', '%%', $s );
                // Escape initial - or @
                if ( strlen( $s ) > 0 && ( $s[0] === '-' || $s[0] === '@' ) ) {
                        $s = '\\' . $s;
                }

                return $s;
        }

        /**
         * Escape a string for ImageMagick's input filenames. See ExpandFilenames()
         * and GetPathComponent() in magick/utility.c.
         *
         * This won't work with an initial ~ or @, so input files should be prefixed
         * with the directory name.
         *
         * Glob character unescaping is broken in ImageMagick before 6.6.1-5, but
         * it's broken in a way that doesn't involve trying to convert every file
         * in a directory, so we're better off escaping and waiting for the bugfix
         * to filter down to users.
         *
         * @param string $path The file path
         * @param bool|string $scene The scene specification, or false if there is none
         * @throws MWException
         * @return string
         */
        function escapeMagickInput( $path, $scene = false ) {
                # Die on initial metacharacters (caller should prepend path)
                $firstChar = substr( $path, 0, 1 );
                if ( $firstChar === '~' || $firstChar === '@' ) {
                        throw new MWException( __METHOD__ . ': cannot escape this path name' );
                }

                # Escape glob chars
                $path = preg_replace( '/[*?\[\]{}]/', '\\\\\0', $path );

                return $this->escapeMagickPath( $path, $scene );
        }

        /**
         * Escape a string for ImageMagick's output filename. See
         * InterpretImageFilename() in magick/image.c.
         * @param string $path The file path
         * @param bool|string $scene The scene specification, or false if there is none
         * @return string
         */
        function escapeMagickOutput( $path, $scene = false ) {
                $path = str_replace( '%', '%%', $path );

                return $this->escapeMagickPath( $path, $scene );
        }

        /**
         * Armour a string against ImageMagick's GetPathComponent(). This is a
         * helper function for escapeMagickInput() and escapeMagickOutput().
         *
         * @param string $path The file path
         * @param bool|string $scene The scene specification, or false if there is none
         * @throws MWException
         * @return string
         */
        protected function escapeMagickPath( $path, $scene = false ) {
                # Die on format specifiers (other than drive letters). The regex is
                # meant to match all the formats you get from "convert -list format"
                if ( preg_match( '/^([a-zA-Z0-9-]+):/', $path, $m ) ) {
                        if ( wfIsWindows() && is_dir( $m[0] ) ) {
                                // OK, it's a drive letter
                                // ImageMagick has a similar exception, see IsMagickConflict()
                        } else {
                                throw new MWException( __METHOD__ . ': unexpected colon character in path name' );
                        }
                }

                # If there are square brackets, add a do-nothing scene specification
                # to force a literal interpretation
                if ( $scene === false ) {
                        if ( strpos( $path, '[' ) !== false ) {
                                $path .= '[0--1]';
                        }
                } else {
                        $path .= "[$scene]";
                }

                return $path;
        }

        /**
         * Retrieve the version of the installed ImageMagick
         * You can use PHPs version_compare() to use this value
         * Value is cached for one hour.
         * @return string Representing the IM version.
         */
        protected function getMagickVersion() {
                global $wgMemc;

                $cache = $wgMemc->get( "imagemagick-version" );
                if ( !$cache ) {
                        global $wgImageMagickConvertCommand;
                        $cmd = wfEscapeShellArg( $wgImageMagickConvertCommand ) . ' -version';
                        wfDebug( __METHOD__ . ": Running convert -version\n" );
                        $retval = '';
                        $return = wfShellExec( $cmd, $retval );
                        $x = preg_match( '/Version: ImageMagick ([0-9]*\.[0-9]*\.[0-9]*)/', $return, $matches );
                        if ( $x != 1 ) {
                                wfDebug( __METHOD__ . ": ImageMagick version check failed\n" );

                                return null;
                        }
                        $wgMemc->set( "imagemagick-version", $matches[1], 3600 );

                        return $matches[1];
                }

                return $cache;
        }

        // FIXME: transformImageMagick() & transformImageMagickExt() uses JPEG quality 80, here it's 95?
        static function imageJpegWrapper( $dst_image, $thumbPath, $quality = 95 ) {
                imageinterlace( $dst_image );
                imagejpeg( $dst_image, $thumbPath, $quality );
        }

        /**
         * Returns whether the current scaler supports rotation (im and gd do)
         *
         * @return bool
         */
        public static function canRotate() {
                $scaler = self::getScalerType( null, false );
                switch ( $scaler ) {
                        case 'im':
                                # ImageMagick supports autorotation
                                return true;
                        case 'imext':
                                # Imagick::rotateImage
                                return true;
                        case 'gd':
                                # GD's imagerotate function is used to rotate images, but not
                                # all precompiled PHP versions have that function
                                return function_exists( 'imagerotate' );
                        default:
                                # Other scalers don't support rotation
                                return false;
                }
        }

        /**
         * @see $wgEnableAutoRotation
         * @return bool Whether auto rotation is enabled
         */
        public static function autoRotateEnabled() {
                global $wgEnableAutoRotation;

                if ( $wgEnableAutoRotation === null ) {
                        // Only enable auto-rotation when the bitmap handler can rotate
                        $wgEnableAutoRotation = BitmapHandler::canRotate();
                }

                return $wgEnableAutoRotation;
        }

        /**
         * @param File $file
         * @param array $params Rotate parameters.
         *   'rotation' clockwise rotation in degrees, allowed are multiples of 90
         * @since 1.21
         * @return bool
         */
        public function rotate( $file, $params ) {
                global $wgImageMagickConvertCommand;

                $rotation = ( $params['rotation'] + $this->getRotation( $file ) ) % 360;
                $scene = false;

                $scaler = self::getScalerType( null, false );
                switch ( $scaler ) {
                        case 'im':
                                $cmd = wfEscapeShellArg( $wgImageMagickConvertCommand ) . " " .
                                        wfEscapeShellArg( $this->escapeMagickInput( $params['srcPath'], $scene ) ) .
                                        " -rotate " . wfEscapeShellArg( "-$rotation" ) . " " .
                                        wfEscapeShellArg( $this->escapeMagickOutput( $params['dstPath'] ) );
                                wfDebug( __METHOD__ . ": running ImageMagick: $cmd\n" );
                                wfProfileIn( 'convert' );
                                $retval = 0;
                                $err = wfShellExecWithStderr( $cmd, $retval );
                                wfProfileOut( 'convert' );
                                if ( $retval !== 0 ) {
                                        $this->logErrorForExternalProcess( $retval, $err, $cmd );

                                        return new MediaTransformError( 'thumbnail_error', 0, 0, $err );
                                }

                                return false;
                        case 'imext':
                                $im = new Imagick();
                                $im->readImage( $params['srcPath'] );
                                if ( !$im->rotateImage( new ImagickPixel( 'white' ), 360 - $rotation ) ) {
                                        return new MediaTransformError( 'thumbnail_error', 0, 0,
                                                "Error rotating $rotation degrees" );
                                }
                                $result = $im->writeImage( $params['dstPath'] );
                                if ( !$result ) {
                                        return new MediaTransformError( 'thumbnail_error', 0, 0,
                                                "Unable to write image to {$params['dstPath']}" );
                                }

                                return false;
                        default:
                                return new MediaTransformError( 'thumbnail_error', 0, 0,
                                        "$scaler rotation not implemented" );
                }
        }

        /**
         * Rerurns whether the file needs to be rendered. Returns true if the
         * file requires rotation and we are able to rotate it.
         *
         * @param File $file
         * @return bool
         */
        public function mustRender( $file ) {
                return self::canRotate() && $this->getRotation( $file ) != 0;
        }
}