Improve picture scaling issues in epub generator

CCBUG: 391625

Test Plan: I tested the file mentioned in the bug report. Pictures look less blurry

Reviewers: #okular

Subscribers: ngraham, aacid, okular-devel

Tags: #okular

Differential Revision: https://phabricator.kde.org/D13766

generators/epub/epubdocument.cpp

@@ -86,9 +86,9 @@ QVariant EpubDocument::loadResource(int type, const QUrl &name)
       const int maxHeight = maxContentHeight();
       const int maxWidth = maxContentWidth();
       if(img.height() > maxHeight)
-        img = img.scaledToHeight(maxHeight);
+        img = img.scaledToHeight(maxHeight, Qt::SmoothTransformation);
       if(img.width() > maxWidth)
-        img = img.scaledToWidth(maxWidth);
+        img = img.scaledToWidth(maxWidth, Qt::SmoothTransformation);
       resource.setValue(img);
       break;
     }