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Use the Wu line anti-alias algorithm for drawing undercurls

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Fixes #853
This commit is contained in:
Kovid Goyal 2018-12-05 14:02:21 +05:30
parent 4cf6373203
commit 3fa7007e91
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GPG Key ID: 06BC317B515ACE7C
1 changed files with 20 additions and 23 deletions
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43
kitty/fonts/render.py
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@ -5,7 +5,7 @@
import ctypes
import sys
from functools import partial
from math import ceil, pi, cos, sqrt
from math import ceil, pi, cos, floor
from kitty.config import defaults
from kitty.constants import is_macos
@ -115,33 +115,30 @@ def add_dline(buf, cell_width, position, thickness, cell_height):
def add_curl(buf, cell_width, position, thickness, cell_height):
xfactor = 2.0 * pi / cell_width
yfactor = max(thickness, 2)
max_x, max_y = cell_width - 1, cell_height - 1
xfactor = 2.0 * pi / max_x
half_height = max(thickness // 2, 1)
def clamp_y(y):
return max(0, min(int(y), cell_height - 1))
def clamp_x(x):
return max(0, min(int(x), cell_width - 1))
def add_intensity(x, y, distance):
def add_intensity(x, y, val):
y += position
y = min(y, max_y)
idx = cell_width * y + x
buf[idx] = min(
255, buf[idx] + int(255 * (1 - distance))
)
buf[idx] = min(255, buf[idx] + val)
# Ensure all space at bottom of cell is used
min_y = clamp_y(ceil(position + yfactor))
if min_y < cell_height - 1:
position += cell_height - 1 - min_y
if position + half_height < max_y:
position += max_y - (position + half_height)
if position + half_height > max_y:
position -= position + half_height - max_y
for x_exact in range(cell_width):
y_exact = yfactor * cos(x_exact * xfactor) + position
y = clamp_y(ceil(y_exact))
x_before, x_after = map(clamp_x, (x_exact - 1, x_exact + 1))
for x in {x_before, x_exact, x_after}:
dist = sqrt((x - x_exact)**2 + (y - y_exact)**2) / 2
add_intensity(x, y, dist)
# Use the Wu antialias algorithm to draw the curve
# cosine waves always have slope <= 1 so are never steep
for x in range(cell_width):
y = half_height * cos(x * xfactor)
y1, y2 = floor(y), ceil(y)
i1 = int(255 * abs(y - y1))
add_intensity(x, y1, 255 - i1)
add_intensity(x, y2, i1)
def render_special(