make internal _color_index one-based again

diff --git a/vectorio/_rectangle.py b/vectorio/_rectangle.py
index f8c8d820bd25f5d517e5f25e6715c1ee13e5bdfa..15880c659c6b6c083c31818d5c77e56367454e85 100644 (file)
--- a/vectorio/_rectangle.py
+++ b/vectorio/_rectangle.py
@@ -52,7 +52,7 @@ class Rectangle(_VectorShape):
         """
         self._width = 1
         self._height = 1
-        self._color_index = color_index
+        self._color_index = color_index + 1
 
         super().__init__(pixel_shader, x, y)
         self.width = width
@@ -86,11 +86,11 @@ class Rectangle(_VectorShape):
     @property
     def color_index(self) -> int:
         """The color_index of the rectangle as 0 based index of the palette."""
-        return self._color_index
+        return self._color_index - 1
 
     @color_index.setter
     def color_index(self, value: int) -> None:
-        self._color_index = abs(value)
+        self._color_index = abs(value + 1)
         self._shape_set_dirty()
 
     def _get_pixel(self, x: int, y: int) -> int: