diff --git a/kcc/comic2ebook.py b/kcc/comic2ebook.py
index e1fd41f..dee5078 100755
--- a/kcc/comic2ebook.py
+++ b/kcc/comic2ebook.py
@@ -256,11 +256,11 @@ def isInFilelist(filename, filelist):
 
 
 def applyImgOptimization(img, isSplit=False, toRight=False):
-    img.optimizeImage(options.gamma)
     img.cropWhiteSpace(10.0)
     if options.cutpagenumbers:
         img.cutPageNumber()
     img.resizeImage(options.upscale, options.stretch, options.black_borders, isSplit, toRight)
+    img.optimizeImage(options.gamma)
     if not options.notquantize:
         img.quantizeImage()
 
diff --git a/kcc/image.py b/kcc/image.py
index 8eeae69..94febca 100755
--- a/kcc/image.py
+++ b/kcc/image.py
@@ -132,6 +132,8 @@ class ComicPage:
             self.image = ImageOps.autocontrast(Image.eval(self.image, lambda a: 255 * (a / 255.) ** gamma))
 
     def quantizeImage(self):
+        self.image = self.image.convert('L')    # convert to grayscale
+        self.image = self.image.convert("RGB")    # convert back to RGB
         colors = len(self.palette) / 3
         if colors < 256:
             self.palette += self.palette[:3] * (256 - colors)