Enable 4:2:0 chroma subsampling for JPEG thumbnails

[lhc/web/wiklou.git] / includes / media / Bitmap.php

diff --git a/includes/media/Bitmap.php b/includes/media/Bitmap.php
index b055d16..ccd345c 100644 (file)
--- a/includes/media/Bitmap.php
+++ b/includes/media/Bitmap.php
@@ -104,6 +104,25 @@ class BitmapHandler extends TransformationalImageHandler {
                return true;
        }
 
+       /**
+        * Get ImageMagick subsampling factors for the target JPEG pixel format.
+        *
+        * @param string $pixelFormat one of 'yuv444', 'yuv422', 'yuv420'
+        * @return array of string keys
+        */
+       protected function imageMagickSubsampling( $pixelFormat ) {
+               switch ( $pixelFormat ) {
+               case 'yuv444':
+                       return [ '1x1', '1x1', '1x1' ];
+               case 'yuv422':
+                       return [ '2x1', '1x1', '1x1' ];
+               case 'yuv420':
+                       return [ '2x2', '1x1', '1x1' ];
+               default:
+                       throw new MWException( 'Invalid pixel format for JPEG output' );
+               }
+       }
+
        /**
         * Transform an image using ImageMagick
         *
@@ -115,7 +134,7 @@ class BitmapHandler extends TransformationalImageHandler {
        protected function transformImageMagick( $image, $params ) {
                # use ImageMagick
                global $wgSharpenReductionThreshold, $wgSharpenParameter, $wgMaxAnimatedGifArea,
-                       $wgImageMagickTempDir, $wgImageMagickConvertCommand, $wgMaxInterlacingAreas;
+                       $wgImageMagickTempDir, $wgImageMagickConvertCommand, $wgJpegPixelFormat;
 
                $quality = [];
                $sharpen = [];
@@ -123,6 +142,7 @@ class BitmapHandler extends TransformationalImageHandler {
                $animation_pre = [];
                $animation_post = [];
                $decoderHint = [];
+               $subsampling = [];
 
                if ( $params['mimeType'] == 'image/jpeg' ) {
                        $qualityVal = isset( $params['quality'] ) ? (string)$params['quality'] : null;
@@ -141,6 +161,10 @@ class BitmapHandler extends TransformationalImageHandler {
                                // JPEG decoder hint to reduce memory, available since IM 6.5.6-2
                                $decoderHint = [ '-define', "jpeg:size={$params['physicalDimensions']}" ];
                        }
+                       if ( $wgJpegPixelFormat ) {
+                               $factors = $this->imageMagickSubsampling( $wgJpegPixelFormat );
+                               $subsampling = [ '-sampling-factor', implode( ',', $factors ) ];
+                       }
                } elseif ( $params['mimeType'] == 'image/png' ) {
                        $quality = [ '-quality', '95' ]; // zlib 9, adaptive filtering
                        if ( $params['interlace'] ) {
@@ -225,6 +249,7 @@ class BitmapHandler extends TransformationalImageHandler {
                        [ '-depth', 8 ],
                        $sharpen,
                        [ '-rotate', "-$rotation" ],
+                       $subsampling,
                        $animation_post,
                        [ $this->escapeMagickOutput( $params['dstPath'] ) ] ) );
 
@@ -251,7 +276,7 @@ class BitmapHandler extends TransformationalImageHandler {
         */
        protected function transformImageMagickExt( $image, $params ) {
                global $wgSharpenReductionThreshold, $wgSharpenParameter, $wgMaxAnimatedGifArea,
-                       $wgMaxInterlacingAreas;
+                       $wgMaxInterlacingAreas, $wgJpegPixelFormat;
 
                try {
                        $im = new Imagick();
@@ -272,6 +297,10 @@ class BitmapHandler extends TransformationalImageHandler {
                                if ( $params['interlace'] ) {
                                        $im->setInterlaceScheme( Imagick::INTERLACE_JPEG );
                                }
+                               if ( $wgJpegPixelFormat ) {
+                                       $factors = $this->imageMagickSubsampling( $wgJpegPixelFormat );
+                                       $im->setSamplingFactors( $factors );
+                               }
                        } elseif ( $params['mimeType'] == 'image/png' ) {
                                $im->setCompressionQuality( 95 );
                                if ( $params['interlace'] ) {