Create a random color generator

app.py

@@ -87,6 +87,18 @@ def sync_hls_to_rgb(key: str):
     st.session_state[key] = f"#{round(r * 255):02x}{round(g * 255):02x}{round(b * 255):02x}"
 
 
+if st.button("🎨 Generate a random color scheme 🎲"):
+    primary_color, text_color, basic_background, secondary_background = util.generate_color_scheme()
+    st.session_state['primaryColor'] = primary_color
+    st.session_state['backgroundColor'] = basic_background
+    st.session_state['secondaryBackgroundColor'] = secondary_background
+    st.session_state['textColor'] = text_color
+    sync_rgb_to_hls('primaryColor')
+    sync_rgb_to_hls('backgroundColor')
+    sync_rgb_to_hls('secondaryBackgroundColor')
+    sync_rgb_to_hls('textColor')
+
+
 def color_picker(label: str, key: str, default_color: str, l_only: bool) -> None:
     col1, col2 = st.columns([1, 3])
     with col1:

util.py

@@ -1,7 +1,58 @@
 import re
+import random
+from colorsys import hls_to_rgb
+
+import wcag_contrast_ratio as contrast
 
 
 def parse_hex(rgb_hex_str: str) -> tuple[float, float, float]:
     if not re.match(r"^#[0-9a-fA-F]{6}$", rgb_hex_str):
         raise ValueError("Invalid hex color")
     return tuple(int(rgb_hex_str[i:i+2], 16) / 255 for i in (1, 3, 5))
+
+
+def random_hls():
+    h = random.random()
+    l = random.random()
+    s = random.random()
+
+    # Make sure the color is light or dark enough.
+    MAX_LIGHTNESS = 0.3
+    if l < 0.5:
+        # Make the color darker.
+        l = l * (MAX_LIGHTNESS / 0.5)
+    else:
+        # Make the color lighter.
+        l = 1 - l
+        l = l * (MAX_LIGHTNESS / 0.5)
+        l = 1 - l
+    return (h, l, s)
+
+
+def high_contrast_color(color):
+    h, l, s = color
+    l = 1 - l
+    return (h, l, s)
+
+
+def hls_to_hex(color):
+    r, g, b = hls_to_rgb(*color)
+    return "#{:02x}{:02x}{:02x}".format(round(r * 255), round(g * 255), round(b * 255))
+
+
+def find_color_with_contrast(base_color, min_contrast_ratio, max_attempts):
+    for _ in range(max_attempts):
+        candidate_color = random_hls()
+        if contrast.rgb(hls_to_rgb(*candidate_color), hls_to_rgb(*base_color)) > min_contrast_ratio:
+            return candidate_color
+    return high_contrast_color(base_color)
+
+
+def generate_color_scheme():
+    primary_color = random_hls()
+    basic_background = high_contrast_color(primary_color)
+
+    text_color = find_color_with_contrast(basic_background, 7, 100)
+    secondary_background = find_color_with_contrast(primary_color, 7, 100)
+
+    return hls_to_hex(primary_color), hls_to_hex(text_color), hls_to_hex(basic_background), hls_to_hex(secondary_background)