Fix some icons being blurry on High DPI screens

Get Qt to use high DPI images when rendering icons. Unfortunately,
turning this on means that non-square images are not rendered properly,
so convert all icons to square images.

src/calibre/devices/hanlin/driver.py

@@ -117,7 +117,7 @@ class BOOX(HANLINV3):
     supported_platforms = ['windows', 'osx', 'linux']
     METADATA_CACHE = '.metadata.calibre'
     DRIVEINFO = '.driveinfo.calibre'
-    icon           = I('devices/boox.jpg')
+    icon           = I('devices/boox.png')
 
     # Ordered list of supported formats
     FORMATS     = ['epub', 'fb2', 'djvu', 'pdf', 'html', 'txt', 'rtf', 'mobi',

src/calibre/devices/kindle/driver.py

@@ -44,7 +44,7 @@ class KINDLE(USBMS):
 
     name           = 'Kindle Device Interface'
     gui_name       = 'Amazon Kindle'
-    icon           = I('devices/kindle.jpg')
+    icon           = I('devices/kindle.png')
     description    = _('Communicate with the Kindle eBook reader.')
     author         = 'John Schember'
     supported_platforms = ['windows', 'osx', 'linux']

src/calibre/devices/nook/driver.py

@@ -22,7 +22,7 @@ class NOOK(USBMS):
     gui_name       = _('The Nook')
     description    = _('Communicate with the Nook eBook reader.')
     author         = 'John Schember'
-    icon           = I('devices/nook.jpg')
+    icon           = I('devices/nook.png')
     supported_platforms = ['windows', 'linux', 'osx']
 
     # Ordered list of supported formats

src/calibre/gui2/__init__.py

@@ -874,6 +874,7 @@ class Application(QApplication):
         qargs = [i.encode('utf-8') if isinstance(i, unicode) else i for i in args]
         self.pi = plugins['progress_indicator'][0]
         QApplication.__init__(self, qargs)
+        self.setAttribute(Qt.AA_UseHighDpiPixmaps)
         if not iswindows:
             self.setup_unix_signals()
         if islinux or isbsd:

src/calibre/utils/img.py

@@ -481,8 +481,9 @@ def test():  # {{{
     from calibre.ptempfile import TemporaryDirectory
     from calibre import CurrentDir
     from glob import glob
+    img = image_from_data(I('lt.png', data=True, allow_user_override=False))
     with TemporaryDirectory() as tdir, CurrentDir(tdir):
-        shutil.copyfile(I('devices/kindle.jpg', allow_user_override=False), 'test.jpg')
+        save_image(img, 'test.jpg')
         ret = optimize_jpeg('test.jpg')
         if ret is not None:
             raise SystemExit('optimize_jpeg failed: %s' % ret)
@@ -495,7 +496,6 @@ def test():  # {{{
             raise SystemExit('optimize_png failed: %s' % ret)
         if glob('*.bak'):
             raise SystemExit('Spurious .bak files left behind')
-    img = image_from_data(I('devices/kindle.jpg', data=True, allow_user_override=False))
     quantize_image(img)
     oil_paint_image(img)
     gaussian_sharpen_image(img)