fix all other webtoon bugs (#1123)

* adjust webtoon thresholds

* fix arbitrary width webtoons

* virtual pages can exceed height by 20%

* prevent webtoon bad options

* adjust virtual page ratio

* don't change history too much

* GUI change

* add TODO

* add scroll illusion

kindlecomicconverter/image.py

@@ -397,6 +397,8 @@ class ComicPage:
             self.image = Image.eval(self.image, lambda a: int(255 * (a / 255.) ** gamma))
 
     def autocontrastImage(self):
+        if self.opt.webtoon:
+            return
         if self.opt.autolevel and not self.color:
             self.convertToGrayscale()
             h = self.image.histogram()