Extract bit depth and color type for PNG images

diff --git a/includes/media/PNGMetadataExtractor.php b/includes/media/PNGMetadataExtractor.php
index 6a931e6..56e6ee9 100644 (file)
--- a/includes/media/PNGMetadataExtractor.php
+++ b/includes/media/PNGMetadataExtractor.php
@@ -25,6 +25,8 @@ class PNGMetadataExtractor {
                $frameCount = 0;
                $loopCount = 1;
                $duration = 0.0;
+               $bitDepth = 0;
+               $colorType = 'unknown';
 
                if (!$filename)
                        throw new Exception( __METHOD__ . ": No file name specified" );
@@ -57,7 +59,35 @@ class PNGMetadataExtractor {
                                throw new Exception( __METHOD__ . ": Read error" );
                        }
 
-                       if ( $chunk_type == "acTL" ) {
+                       if ( $chunk_type == "IHDR" ) {
+                               $buf = fread( $fh, $chunk_size );
+                               if( !$buf ) {
+                                       throw new Exception( __METHOD__ . ": Read error" );
+                               }
+                               $bitDepth = ord( substr( $buf, 8, 1 ) );
+                               // Detect the color type in British English as per the spec
+                               // http://www.w3.org/TR/PNG/#11IHDR
+                               switch ( ord( substr( $buf, 9, 1 ) ) ) {
+                                       case 0:
+                                               $colorType = 'greyscale';
+                                               break;
+                                       case 2: 
+                                               $colorType = 'truecolour';
+                                               break;
+                                       case 3:
+                                               $colorType = 'index-coloured';
+                                               break;
+                                       case 4:
+                                               $colorType = 'greyscale-alpha';
+                                               break;
+                                       case 6:
+                                               $colorType = 'truecolour-alpha';
+                                               break;
+                                       default:
+                                               $colorType = 'unknown';
+                                               break;
+                               }
+                       } elseif ( $chunk_type == "acTL" ) {
                                $buf = fread( $fh, $chunk_size );
                                if( !$buf ) {
                                        throw new Exception( __METHOD__ . ": Read error" );
@@ -97,7 +127,9 @@ class PNGMetadataExtractor {
                return array(
                        'frameCount' => $frameCount,
                        'loopCount' => $loopCount,
-                       'duration' => $duration
+                       'duration' => $duration,
+                       'bitDepth' => $bitDepth,
+                       'colorType' => $colorType,
                );
                
        }