Update palette in quantize

Tests/test_image_quantize.py

@@ -38,9 +38,10 @@ class TestImageQuantize(PillowTestCase):
 
     def test_rgba_quantize(self):
         image = hopper('RGBA')
-        image.quantize()
         self.assertRaises(ValueError, image.quantize, method=0)
 
+        self.assertEqual(image.quantize().convert().mode, "RGBA")
+
     def test_quantize(self):
         image = Image.open('Tests/images/caption_6_33_22.png').convert('RGB')
         converted = image.quantize()

src/PIL/Image.py

@@ -1096,7 +1096,13 @@ class Image(object):
             im = self.im.convert("P", dither, palette.im)
             return self._new(im)
 
-        return self._new(self.im.quantize(colors, method, kmeans))
+        im = self._new(self.im.quantize(colors, method, kmeans))
+
+        from . import ImagePalette
+        mode = im.im.getpalettemode()
+        im.palette = ImagePalette.ImagePalette(mode, im.im.getpalette(mode, mode))
+
+        return im
 
     def copy(self):
         """

src/libImaging/Unpack.c

@@ -1331,6 +1331,7 @@ static struct {
     {"RGB",     "BGR;5",        16,     ImagingUnpackBGR15}, /* compat */
     {"RGB",     "RGBX",         32,     copy4},
     {"RGB",     "RGBX;L",       32,     unpackRGBAL},
+    {"RGB",     "RGBA;L",       32,     unpackRGBAL},
     {"RGB",     "BGRX",         32,     ImagingUnpackBGRX},
     {"RGB",     "XRGB",         24,     ImagingUnpackXRGB},
     {"RGB",     "XBGR",         32,     ImagingUnpackXBGR},