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from typing import Tuple, Dict, List
import curses
import hashlib
import math
from . import hsluv
Palette = Dict[float, int]
# BT.601 (YCbCr) constants, see XEP-0392
K_R = 0.299
K_G = 0.587
K_B = 1 - K_R - K_G
def ncurses_color_to_rgb(color: int) -> Tuple[float, float, float]:
if color <= 15:
try:
(r, g, b) = curses.color_content(color)
except: # fallback in faulty terminals (e.g. xterm)
(r, g, b) = curses.color_content(color % 8)
r = r / 1000 * 5
g = g / 1000 * 5
b = b / 1000 * 5
elif color <= 231:
color = color - 16
b = color % 6
color = color // 6
g = color % 6
color = color // 6
r = color % 6
else:
color -= 232
r = g = b = color / 24 * 5
return r / 5, g / 5, b / 5
def generate_ccg_palette(curses_palette: List[int],
reference_y: float) -> Palette:
cbcr_palette = {} # type: Dict[float, Tuple[float, int]]
for curses_color in curses_palette:
r, g, b = ncurses_color_to_rgb(curses_color)
# drop grayscale
if r == g == b:
continue
h, _, y = hsluv.rgb_to_hsluv((r, g, b))
# this is to keep the code compatible with earlier versions of XEP-0392
y = y / 100
key = round(h)
try:
existing_y, *_ = cbcr_palette[key]
except KeyError:
pass
else:
if abs(existing_y - reference_y) <= abs(y - reference_y):
continue
cbcr_palette[key] = y, curses_color
return {
angle: curses_color
for angle, (_, curses_color) in cbcr_palette.items()
}
def text_to_angle(text: str) -> float:
hf = hashlib.sha1()
hf.update(text.encode("utf-8"))
hue = int.from_bytes(hf.digest()[:2], "little")
return hue / 65535 * 360
def ccg_palette_lookup(palette: Palette, angle: float) -> int:
# try quick lookup first
try:
return palette[round(angle)]
except KeyError:
pass
best_metric = float("inf")
best = None
for anglep, color in palette.items():
metric = abs(anglep - angle)
if metric < best_metric:
best_metric = metric
best = color
return best
def ccg_text_to_color(palette, text: str) -> int:
angle = text_to_angle(text)
return ccg_palette_lookup(palette, angle)
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