new Color class replacing bare hex strings, WCAG contrast ratio and relative luminance functions, allow automatic selection of more ideal contrasting colors

constants.py

@@ -1,3 +1,7 @@
+from typing import List
+
+import webcolors
+
 HEADER_LENGTH = 10
 
 
@@ -24,17 +28,118 @@ class Requests:
     GET_HISTORY = 'GET_HISTORY'  # Send a short history of the chat to the client
 
 
+class Color():
+    """
+    Describes a basic RGB color.
+    """
+
+    def __init__(self, name: str, hex: str) -> None:
+        self.name, self.hex = name, hex
+        self.rgb = webcolors.hex_to_rgb(hex)
+
+    def __repr__(self) -> str:
+        return f'Color({self.name})'
+
+    @property
+    def id(self) -> str:
+        return '_'.join(self.name.split()).upper()
+
+    def relative_luminance(self) -> float:
+        """
+        Calculates the relative luminance of a given color, according to WCAG guidelines.
+
+        https://www.w3.org/TR/WCAG20/#relativeluminancedef
+
+        :return: The relative luminance of this color.
+        """
+        r, g, b = self.rgb.red / 255, self.rgb.green / 255, self.rgb.blue / 255
+        r = r / 12.92 if r <= 0.03928 else ((r + 0.055) / 1.055) ** 2.4
+        g = g / 12.92 if g <= 0.03928 else ((g + 0.055) / 1.055) ** 2.4
+        b = b / 12.92 if b <= 0.03928 else ((b + 0.055) / 1.055) ** 2.4
+        return 0.2126 * r + 0.7152 * g + 0.0722 * b
+
+    def contrast_ratio(self, other: 'Color') -> float:
+        """
+        Calculates the relative contrast between two colors in a ratio from 1:1 to 21:1, according to WCAG guidelines.
+
+        https://www.w3.org/TR/WCAG20/#contrast-ratiodef
+
+        :param other: The darker color.
+        :return:
+        """
+        l1 = self.relative_luminance()
+        l2 = other.relative_luminance()
+        return (l1 + 0.05) / (l2 + 0.05)
+
+
 class Colors:
     """
     Stores hexadecimal color codes of popular colors, with names.
     """
 
-    ALL_NAMES = ['Aqua', 'Azure', 'Beige', 'Black', 'Blue', 'Brown', 'Cyan', 'Dark Blue', 'Dark Cyan', 'Dark Grey',
-                 'Dark Green', 'Dark Khaki', 'Dark Magenta', 'Dark Olive Green', 'Dark Orange', ' Dark Orchid', 'Dark Red', 'Dark Salmon',
-                 'Dark Violet', 'Fuchsia', 'Gold', 'Green', 'Indigo', 'Khaki', 'Light Blue', 'Light Cyan',
-                 'Light Green', 'Light Grey', 'Light Pink', 'Light Yellow', 'Lime', 'Magenta', 'Maroon', 'Navy',
-                 'Olive', 'Orange', 'Pink', 'Purple', 'Violet', 'Red', 'Silver', 'White', 'Yellow']
+    AQUA = Color("Aqua", "#00ffff")
+    AZURE = Color("Azure", "#f0ffff")
+    BEIGE = Color("Beige", "#f5f5dc")
+    BLACK = Color("Black", "#000000")
+    BLUE = Color("Blue", "#0000ff")
+    BROWN = Color("Brown", "#a52a2a")
+    CYAN = Color("Cyan", "#00ffff")
+    DARKBLUE = Color("Dark Blue", "#00008b")
+    DARKCYAN = Color("Dark Cyan", "#008b8b")
+    DARKGREY = Color("Dark Grey", "#a9a9a9")
+    DARKGREEN = Color("Dark Green", "#006400")
+    DARKKHAKI = Color("Dark Khaki", "#bdb76b")
+    DARKMAGENTA = Color("Dark Magenta", "#8b008b")
+    DARKOLIVEGREEN = Color("Dark Olive Green", "#556b2f")
+    DARKORANGE = Color("Dark Orange", "#ff8c00")
+    DARKORCHID = Color("Dark Orchid", "#9932cc")
+    DARKRED = Color("Dark Red", "#8b0000")
+    DARKSALMON = Color("Dark Salmon", "#e9967a")
+    DARKVIOLET = Color("Dark Violet", "#9400d3")
+    FUCHSIA = Color("Fuchsia", "#ff00ff")
+    GOLD = Color("Gold", "#ffd700")
+    GREEN = Color("Green", "#008000")
+    INDIGO = Color("Indigo", "#4b0082")
+    KHAKI = Color("Khaki", "#f0e68c")
+    LIGHTBLUE = Color("Light Blue", "#add8e6")
+    LIGHTCYAN = Color("Light Cyan", "#e0ffff")
+    LIGHTGREEN = Color("Light Green", "#90ee90")
+    LIGHTGREY = Color("Light Grey", "#d3d3d3")
+    LIGHTPINK = Color("Light Pink", "#ffb6c1")
+    LIGHTYELLOW = Color("Light Yellow", "#ffffe0")
+    LIME = Color("Lime", "#00ff00")
+    MAGENTA = Color("Magenta", "#ff00ff")
+    MAROON = Color("Maroon", "#800000")
+    NAVY = Color("Navy", "#000080")
+    OLIVE = Color("Olive", "#808000")
+    ORANGE = Color("Orange", "#ffa500")
+    PINK = Color("Pink", "#ffc0cb")
+    PURPLE = Color("Purple", "#800080")
+    VIOLET = Color("Violet", "#800080")
+    RED = Color("Red", "#ff0000")
+    SILVER = Color("Silver", "#c0c0c0")
+    WHITE = Color("White", "#ffffff")
+    YELLOW = Color("Yellow", "#ffff00")
+
     ALL = [AQUA, AZURE, BEIGE, BLACK, BLUE, BROWN, CYAN, DARKBLUE, DARKCYAN, DARKGREY, DARKGREEN, DARKKHAKI,
            DARKMAGENTA, DARKOLIVEGREEN, DARKORANGE, DARKORCHID, DARKRED, DARKSALMON, DARKVIOLET, FUCHSIA, GOLD, GREEN,
            INDIGO, KHAKI, LIGHTBLUE, LIGHTCYAN, LIGHTGREEN, LIGHTGREY, LIGHTPINK, LIGHTYELLOW, LIME, MAGENTA, MAROON,
-           NAVY, OLIVE, ORANGE, PINK, PURPLE, VIOLET, RED, SILVER, WHITE, YELLOW, ]
+           NAVY, OLIVE, ORANGE, PINK, PURPLE, VIOLET, RED, SILVER, WHITE, YELLOW]
+
+    @staticmethod
+    def has_contrast(ratio: float, background: Color = WHITE) -> List[Color]:
+        """
+        Returns a list of Color objects with contrast ratios above the given minimum.
+
+        :param ratio: The minimum contrast ratio each color must adhere to.
+        :param background: Defaults to White, the background (lighter) for the other contrasting colors to be compared to.
+        :return: A list of Color objects with contrast ratios above the given minimum.
+        """
+        above_ratio = []
+
+        for color in Colors.ALL:
+            contrast = background.contrast_ratio(color)
+            if contrast >= ratio:
+                above_ratio.append(color)
+
+        return above_ratio