Cover cache: Resize covers larger than 600x800 in the cover cache to reduce memory consumption in the GUI

src/calibre/library/caches.py

@@ -10,14 +10,14 @@ import collections, glob, os, re, itertools, functools
 from itertools import repeat
 from datetime import timedelta
 
-from PyQt4.QtCore import QThread, QReadWriteLock
-from PyQt4.QtGui import QImage
+from PyQt4.Qt import QThread, QReadWriteLock, QImage, Qt
 
 from calibre.utils.config import tweaks
 from calibre.utils.date import parse_date, now, UNDEFINED_DATE
 from calibre.utils.search_query_parser import SearchQueryParser
 from calibre.utils.pyparsing import ParseException
 from calibre.ebooks.metadata import title_sort
+from calibre import fit_image
 
 class CoverCache(QThread):
 
@@ -96,6 +96,11 @@ class CoverCache(QThread):
                         img.loadFromData(data)
                         if img.isNull():
                             continue
+                        scaled, nwidth, nheight = fit_image(img.width(),
+                                img.height(), 600, 800)
+                        if scaled:
+                            img = img.scaled(nwidth, nheight, Qt.KeepAspectRatio,
+                                    Qt.SmoothTransformation)
                     except:
                         continue
                     self.cache_lock.lockForWrite()