Improve processing performance by partially undoing "Refactored detection of corrupted files"

Commit f952634971 moved image corruption detection out from the ComicPage constructor and into a standalone detectCorruption() function. This led to a performance regression because now corruption detection happens in a single thread when it used to be distributed across worker threads, and because a source image is now loaded twice in memory: once during corruption detection and once when actually going to process the image.

Image file corruption detection is now back inside the ComicPage constructor and the extra load() has been removed because the convert() call will automatically invoke load() and most likely throw the same exceptions.

kindlecomicconverter/image.py

@@ -141,7 +141,13 @@ class ComicPageParser:
         self.source = source
         self.size = self.opt.profileData[1]
         self.payload = []
-        self.image = Image.open(os.path.join(source[0], source[1])).convert('RGB')
+
+        # Detect corruption in source image, let caller catch any exceptions triggered.
+        srcImgPath = os.path.join(source[0], source[1])
+        self.image = Image.open(srcImgPath)
+        self.image.verify()
+        self.image = Image.open(srcImgPath).convert('RGB')
+
         self.color = self.colorCheck()
         self.fill = self.fillCheck()
         # backwards compatibility for Pillow >9.1.0