Improve DjVu support

lector/threaded.py

@@ -25,11 +25,17 @@ from PyQt5 import QtCore, QtGui
 from lector import sorter
 from lector import database
 
+# The following have to be separate
 try:
     from lector.parsers.pdf import render_pdf_page
 except ImportError:
     pass
 
+try:
+    from lector.parsers.djvu import render_djvu_page
+except ImportError:
+    pass
+
 logger = logging.getLogger(__name__)
 
 
@@ -165,6 +171,10 @@ class BackGroundCacheRefill(QtCore.QThread):
                 page_data = self.book.loadPage(current_page)
                 pixmap = render_pdf_page(page_data)
 
+            elif self.filetype == 'djvu':
+                page_data = self.book.pages[current_page]
+                pixmap = render_djvu_page(page_data)
+
             return pixmap
 
         remove_index = self.image_cache.index(self.remove_value)