Rename Röntgen to Map Machine.

map_machine/color.py

@@ -0,0 +1,53 @@
+"""
+Color utility.
+"""
+from typing import Any
+
+from colour import Color
+
+from map_machine.util import MinMax
+
+__author__ = "Sergey Vartanov"
+__email__ = "me@enzet.ru"
+
+
+def is_bright(color: Color) -> bool:
+    """
+    Check whether color bright enough to have black outline instead of white.
+    """
+    return (
+        0.2126 * color.red + 0.7152 * color.green + 0.0722 * color.blue
+        > 0.78125
+    )
+
+
+def get_gradient_color(
+    value: Any, bounds: MinMax, colors: list[Color]
+) -> Color:
+    """
+    Get color from the color scale for the value.
+
+    :param value: given value (should be in bounds)
+    :param bounds: maximum and minimum values
+    :param colors: color scale
+    """
+    color_length: int = len(colors) - 1
+    scale: list[Color] = colors + [Color("black")]
+
+    range_coefficient: float = (
+        0 if bounds.is_empty() else (value - bounds.min_) / bounds.delta()
+    )
+    # If value is out of range, set it to boundary value.
+    range_coefficient = min(1.0, max(0.0, range_coefficient))
+    index: int = int(range_coefficient * color_length)
+    coefficient: float = (
+        range_coefficient - index / color_length
+    ) * color_length
+
+    return Color(
+        rgb=[
+            scale[index].rgb[i]
+            + coefficient * (scale[index + 1].rgb[i] - scale[index].rgb[i])
+            for i in range(3)
+        ]
+    )