The bitmap preview class now takes maxX and maxY into consideration

This is a fix for owncloud#13607 and is part of the global programme: owncloud#13609

The image aspect ratio is kept intact.

diff --git a/lib/private/preview/bitmap.php b/lib/private/preview/bitmap.php
index 04496f7e1dfc848723a110ab33a28b7cf4bb690a..3071c7887241db5635c3835eb91b9d544fa09b1c 100644 (file)
--- a/lib/private/preview/bitmap.php
+++ b/lib/private/preview/bitmap.php
@@ -2,7 +2,7 @@
 /**
  * @author Joas Schilling <nickvergessen@owncloud.com>
  * @author Morris Jobke <hey@morrisjobke.de>
- * @author Olivier Paroz <github@oparoz.com>
+ * @author Olivier Paroz <owncloud@interfasys.ch>
  *
  * @copyright Copyright (c) 2015, ownCloud, Inc.
  * @license AGPL-3.0
@@ -23,30 +23,91 @@
 
 namespace OC\Preview;
 
+use Imagick;
+
+/**
+ * Creates a PNG preview using ImageMagick via the PECL extension
+ *
+ * @package OC\Preview
+ */
 abstract class Bitmap extends Provider {
+
        /**
         * {@inheritDoc}
         */
        public function getThumbnail($path, $maxX, $maxY, $scalingup, $fileview) {
+
                $tmpPath = $fileview->toTmpFile($path);
+               if (!$tmpPath) {
+                       return false;
+               }
 
-               //create imagick object from bitmap or vector file
+               // Creates \Imagick object from bitmap or vector file
                try {
-                       // Layer 0 contains either the bitmap or
-                       // a flat representation of all vector layers
-                       $bp = new \Imagick($tmpPath . '[0]');
-
-                       $bp->setImageFormat('png');
+                       $bp = $this->getResizedPreview($tmpPath, $maxX, $maxY);
                } catch (\Exception $e) {
-                       \OC_Log::write('core', $e->getmessage(), \OC_Log::ERROR);
+                       \OC_Log::write('core', 'ImageMagick says: ' . $e->getmessage(), \OC_Log::ERROR);
                        return false;
                }
 
                unlink($tmpPath);
 
                //new bitmap image object
-               $image = new \OC_Image($bp);
+               $image = new \OC_Image();
+               $image->loadFromData($bp);
                //check if image object is valid
                return $image->valid() ? $image : false;
        }
+
+       /**
+        * Returns a preview of maxX times maxY dimensions in PNG format
+        *
+        *    * The default resolution is already 72dpi, no need to change it for a bitmap output
+        *    * It's possible to have proper colour conversion using profileimage().
+        *    ICC profiles are here: http://www.color.org/srgbprofiles.xalter
+        *    * It's possible to Gamma-correct an image via gammaImage()
+        *
+        * @param string $tmpPath the location of the file to convert
+        * @param int $maxX
+        * @param int $maxY
+        *
+        * @return \Imagick
+        */
+       private function getResizedPreview($tmpPath, $maxX, $maxY) {
+               $bp = new Imagick();
+
+               // Layer 0 contains either the bitmap or a flat representation of all vector layers
+               $bp->readImage($tmpPath . '[0]');
+
+               $bp = $this->resize($bp, $maxX, $maxY);
+
+               $bp->setImageFormat('png');
+
+               return $bp;
+       }
+
+       /**
+        * Returns a resized \Imagick object
+        *
+        * If you want to know more on the various methods available to resize an
+        * image, check out this link : @link https://stackoverflow.com/questions/8517304/what-the-difference-of-sample-resample-scale-resize-adaptive-resize-thumbnail-im
+        *
+        * @param \Imagick $bp
+        * @param int $maxX
+        * @param int $maxY
+        *
+        * @return \Imagick
+        */
+       private function resize($bp, $maxX, $maxY) {
+               list($previewWidth, $previewHeight) = array_values($bp->getImageGeometry());
+
+               // We only need to resize a preview which doesn't fit in the maximum dimensions
+               if ($previewWidth > $maxX || $previewHeight > $maxY) {
+                       // TODO: LANCZOS is the default filter, CATROM could bring similar results faster
+                       $bp->resizeImage($maxX, $maxY, imagick::FILTER_LANCZOS, 1, true);
+               }
+
+               return $bp;
+       }
+
 }