Fix preview generation for office documents

`new \imagick()` returns an object, but we need the image blob (binary
string) from this object.

This is a partial backport of #26531, which brings a lot of refactoring
but also contains the fix.

Fixes: #29956
Signed-off-by: Jonas Meurer <jonas@freesources.org>

diff --git a/lib/private/Preview/Office.php b/lib/private/Preview/Office.php
index fef218823e21d42e30dc4c63e38069ecbb443c78..50c016737ece94569f9b3083bb9ab8e15a976f46 100644 (file)
--- a/lib/private/Preview/Office.php
+++ b/lib/private/Preview/Office.php
@@ -74,7 +74,7 @@ abstract class Office extends ProviderV2 {
                }
 
                $image = new \OC_Image();
-               $image->loadFromData($png);
+               $image->loadFromData((string) $png);
 
                $this->cleanTmpFiles();
                unlink($pngPreview);