charts.color

from .charts_color_types import Rgb

_HEX = "0123456789abcdef"


def _nibble(ch: str, hex: str) -> int:
    n = _HEX.find(ch.lower())
    if n < 0:
        raise ValueError('"%s" is not a hex colour (#rgb or #rrggbb)' % (hex,))
    return n


def parse_hex(hex: str) -> Rgb:  # noqa: A002 - the manifest names it hex
    """"#rrggbb" or the short "#rgb" (digits doubled, as CSS does), either case."""
    if not isinstance(hex, str) or not hex.startswith("#") or len(hex) not in (4, 7):
        raise ValueError('"%s" is not a hex colour (#rgb or #rrggbb)' % (hex,))
    if len(hex) == 4:
        return Rgb(r=_nibble(hex[1], hex) * 17, g=_nibble(hex[2], hex) * 17, b=_nibble(hex[3], hex) * 17)
    return Rgb(
        r=_nibble(hex[1], hex) * 16 + _nibble(hex[2], hex),
        g=_nibble(hex[3], hex) * 16 + _nibble(hex[4], hex),
        b=_nibble(hex[5], hex) * 16 + _nibble(hex[6], hex),
    )

from .charts_color_types import Rgb

_HEX = "0123456789abcdef"


def _pair(value: int) -> str:
    if isinstance(value, bool) or not isinstance(value, int) or value < 0 or value > 255:
        raise ValueError("rgb channels must be whole numbers from 0 to 255, received %r" % (value,))
    return _HEX[value // 16] + _HEX[value % 16]


def to_hex(rgb: Rgb) -> str:
    """Lowercase "#rrggbb", the form every renderer accepts."""
    return "#" + _pair(rgb.r) + _pair(rgb.g) + _pair(rgb.b)

Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.

from .math_pow import pow  ← from math.pow ^1.0.0 · built alongside by fune
from .math_round_float import round_float  ← from math.round-float ^1.0.0 · built alongside by fune


def srgb_to_linear(channel: int) -> float:
    """The sRGB transfer function (IEC 61966-2-1) undone: an 8-bit channel as
    linear light from 0 to 1, rounded to 12 places."""
    if isinstance(channel, bool) or not isinstance(channel, int) or channel < 0 or channel > 255:
        raise ValueError("channel must be a whole number from 0 to 255, received %r" % (channel,))
    c = channel / 255
    linear = c / 12.92 if c <= 0.04045 else pow((c + 0.055) / 1.055, 2.4)
    return round_float(linear, 12)

Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.

import math

from .math_pow import pow  ← from math.pow ^1.0.0 · built alongside by fune
from .math_round_float import round_float  ← from math.round-float ^1.0.0 · built alongside by fune


def linear_to_srgb(value: float) -> int:
    """Linear light back to an 8-bit sRGB channel, clipping to 0..1 first."""
    if isinstance(value, bool) or not isinstance(value, (int, float)) or not math.isfinite(value):
        raise ValueError("value must be a finite number, received %r" % (value,))
    v = 0.0 if value < 0 else 1.0 if value > 1 else float(value)
    encoded = 12.92 * v if v <= 0.0031308 else 1.055 * pow(v, 1 / 2.4) - 0.055
    return int(round_float(encoded * 255, 0))