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Reformat / minimize some color-related math #3592

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merged 2 commits into from
Jul 1, 2025
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Reformat / minimize some color-related math #3592

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673bf2a
Minimize some color math
HalfWhitt Jun 28, 2025
b5a6b81
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HalfWhitt Jun 28, 2025
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1 change: 1 addition & 0 deletions changes/3592.misc.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Some of the math in travertino.colors has been reformatted for readability.
154 changes: 40 additions & 114 deletions travertino/src/travertino/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,14 @@
from .constants import * # noqa: F403


def _clamp(value, upper=1):
return min(upper, max(0, value))


def _clamp_hex(value):
return round(_clamp(value, upper=255))


class Color:
"A base class for all colorspace representations."

Expand Down Expand Up @@ -57,63 +65,27 @@ def blend_over(
if front_color.a == 1:
# If the front color is fully opaque then the result will be the same as
# front color.
return front_color.rgba
return front_color

blended_alpha = min(
1, max(0, (front_color.a + ((1 - front_color.a) * back_color.a)))
)
blended_alpha = _clamp(front_color.a + ((1 - front_color.a) * back_color.a))

if blended_alpha == 0:
# Don't further blend the color, to prevent divide by 0.
return rgba(0, 0, 0, 0)
else:
blended_color = rgba(
# Red Component
min(
255,
max(
0,
round(
(
(front_color.r * front_color.a)
+ (back_color.r * back_color.a * (1 - front_color.a))
)
/ blended_alpha
),
),
),
# Green Component
min(
255,
max(
0,
round(
(
(front_color.g * front_color.a)
+ (back_color.g * back_color.a * (1 - front_color.a))
)
/ blended_alpha
),
),
),
# Blue Component
min(
255,
max(
0,
round(
(
(front_color.b * front_color.a)
+ (back_color.b * back_color.a * (1 - front_color.a))
)
/ blended_alpha
),
),
),
# Alpha component
min(1, max(0, blended_alpha)),
)
return blended_color
bands = {}
for band in "rgb":
front = getattr(front_color, band)
back = getattr(back_color, band)
bands[band] = _clamp_hex(
(
(front * front_color.a)
+ (back * back_color.a * (1 - front_color.a))
)
/ blended_alpha
)

return rgba(**bands, a=blended_alpha)

def unblend_over(self, back_color: Color, front_color_alpha: float) -> rgba:
"""Performs the reverse of the "over" straight alpha blending operation,
Expand Down Expand Up @@ -145,70 +117,24 @@ def unblend_over(self, back_color: Color, front_color_alpha: float) -> rgba:

blended_color = self.rgba
back_color = back_color.rgba
if not (0 < front_color_alpha <= 1):
if not 0 < front_color_alpha <= 1:
raise ValueError(
"The value of front_color_alpha must be within the range of (0, 1]."
)
else:
front_color = rgba(
# Red Component
min(
255,
max(
0,
round(
(
(blended_color.r * blended_color.a)
- (
back_color.r
* back_color.a
* (1 - front_color_alpha)
)
)
/ front_color_alpha
),
),
),
# Green Component
min(
255,
max(
0,
round(
(
(blended_color.g * blended_color.a)
- (
back_color.g
* back_color.a
* (1 - front_color_alpha)
)
)
/ front_color_alpha
),
),
),
# Blue Component
min(
255,
max(
0,
round(
(
(blended_color.b * blended_color.a)
- (
back_color.b
* back_color.a
* (1 - front_color_alpha)
)
)
/ front_color_alpha
),
),
),
# Alpha Component
front_color_alpha,
)
return front_color.rgba
bands = {}
for band in "rgb":
blended = getattr(blended_color, band)
back = getattr(back_color, band)
bands[band] = _clamp_hex(
(
(blended * blended_color.a)
- (back * back_color.a * (1 - front_color_alpha))
)
/ front_color_alpha
)

return rgba(**bands, a=front_color_alpha)


class rgba(Color):
Expand Down Expand Up @@ -276,9 +202,9 @@ def hsla(self) -> hsla:

return hsla(
hue % 360, # [0,360)
min(1, max(0, saturation)), # [0,1]
min(1, max(0, lightness)), # [0,1]
min(1, max(0, self.a)), # [0,1]
_clamp(saturation), # [0,1]
_clamp(lightness), # [0,1]
self.a, # [0,1]
)

@property
Expand Down