Sideband/sbapp/kivymd/theming_dynamic_text.py

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2022-07-07 14:16:10 -06:00
"""
Theming Dynamic Text
====================
Two implementations. The first is based on color brightness obtained from-
https://www.w3.org/TR/AERT#color-contrast
The second is based on relative luminance calculation for sRGB obtained from-
https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
and contrast ratio calculation obtained from-
https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
Preliminary testing suggests color brightness more closely matches the
`Material Design spec` suggested text colors, but the alternative implementation
is both newer and the current 'correct' recommendation, so is included here
as an option.
"""
def _color_brightness(color):
# Implementation of color brightness method
brightness = color[0] * 299 + color[1] * 587 + color[2] * 114
brightness = brightness
return brightness
def _black_or_white_by_color_brightness(color):
if _color_brightness(color) >= 500:
return "black"
else:
return "white"
def _normalized_channel(color):
# Implementation of contrast ratio and relative luminance method
if color <= 0.03928:
return color / 12.92
else:
return ((color + 0.055) / 1.055) ** 2.4
def _luminance(color):
rg = _normalized_channel(color[0])
gg = _normalized_channel(color[1])
bg = _normalized_channel(color[2])
return 0.2126 * rg + 0.7152 * gg + 0.0722 * bg
def _black_or_white_by_contrast_ratio(color):
l_color = _luminance(color)
l_black = 0.0
l_white = 1.0
b_contrast = (l_color + 0.05) / (l_black + 0.05)
w_contrast = (l_white + 0.05) / (l_color + 0.05)
return "white" if w_contrast >= b_contrast else "black"
def get_contrast_text_color(color, use_color_brightness=True):
if use_color_brightness:
contrast_color = _black_or_white_by_color_brightness(color)
else:
contrast_color = _black_or_white_by_contrast_ratio(color)
if contrast_color == "white":
return 1, 1, 1, 1
else:
return 0, 0, 0, 1
if __name__ == "__main__":
from kivy.utils import get_color_from_hex
from kivymd.color_definitions import colors, text_colors
for c in colors.items():
if c[0] in ["Light", "Dark"]:
continue
color = c[0]
print(f"For the {color} color palette:")
for name, hex_color in c[1].items():
if hex_color:
col = get_color_from_hex(hex_color)
col_bri = get_contrast_text_color(col)
con_rat = get_contrast_text_color(
col, use_color_brightness=False
)
text_color = text_colors[c[0]][name]
print(
f" The {name} hue gives {col_bri} using color "
f"brightness, {con_rat} using contrast ratio, and "
f"{text_color} from the MD spec"
)