Run color inversion logic code when image instance is created

The attribute name is more readable this way.

weasyprint/images.py

@@ -66,7 +66,12 @@ def __init__(self, pillow_image, image_id, image_data, filename=None,
         self.height = pillow_image.height
         self.ratio = (self.width / self.height) if self.height != 0 else inf
         self.optimize = optimize = options['optimize_images']
-        self.app14 = getattr(original_pillow_image, 'app', {}).get('APP14')
+
+        # The presence of the APP14 segment indicates an Adobe image with
+        # inverted CMYK data. Specify a Decode Array to invert it again back to
+        # normal. See https://github.com/Kozea/WeasyPrint/pull/2179.
+        app14 = getattr(original_pillow_image, 'app', {}).get('APP14')
+        self.invert_colors = self.mode == 'CMYK' and app14 is not None
 
         if pillow_image.format in ('JPEG', 'MPO'):
             self.format = 'JPEG'
@@ -151,11 +156,8 @@ def get_x_object(self, interpolate, dpi_ratio):
         })
 
         if self.format == 'JPEG':
-            if self.mode == 'CMYK' and self.app14 is not None:
-                # The presence of the APP14 segment indicates an Adobe image
-                # with inverted CMYK data. Specify a Decode Array to invert
-                # it again back to normal.
-                extra['Decode'] = '[1 0 1 0 1 0 1 0]'
+            if self.invert_colors:
+                extra['Decode'] = pydyf.Array((1, 0) * 4)
             extra['Filter'] = '/DCTDecode'
             return pydyf.Stream([self.image_data], extra)