[utils] Return exactly num_colors colors from get_colors

doctr/utils/visualization.py

@@ -145,8 +145,9 @@ def get_colors(num_colors: int) -> list[tuple[float, float, float]]:
         colors: list of generated colors
     """
     colors = []
-    for i in np.arange(0.0, 360.0, 360.0 / num_colors):
-        hue = i / 360.0
+    # Integer steps give exactly num_colors hues (a float step can add one more, close to 360°, i.e. red again)
+    for i in range(num_colors):
+        hue = i / num_colors
         lightness = (50 + np.random.rand() * 10) / 100.0
         saturation = (90 + np.random.rand() * 10) / 100.0
         colors.append(colorsys.hls_to_rgb(hue, lightness, saturation))

tests/common/test_utils_visualization.py

@@ -69,6 +69,13 @@ def test_visualize_kie_page():
     assert len(fig.axes[0].texts) == 0
 
 
+@pytest.mark.parametrize("num_colors", [0, 1, 3, 161, 175])
+def test_get_colors(num_colors):
+    colors = visualization.get_colors(num_colors)
+    assert len(colors) == num_colors
+    assert all(len(color) == 3 and all(0 <= c <= 1 for c in color) for color in colors)
+
+
 def test_draw_boxes():
     image = np.ones((256, 256, 3), dtype=np.float32)
     boxes = [