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gradients.py
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gradients.py
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
gradients
---------
Functions for creating gradient graphics.
.. note:: CSS3 gradients are better than image gradient strips in most cases.
See http://www.colorzilla.com/gradient-editor/
"""
from colors import rgb
try:
import cairo
except ImportError:
import cairocffi as cairo
def vertical_strip(width=10, height=100, color=rgb(100, 100, 100),
subtlety=0.1):
"""
Draws a subtle vertical gradient strip.
"""
cairo_color = color / rgb(255, 255, 255)
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
ctx = cairo.Context(surface)
ctx.scale(width / 1.0, height / 1.0)
pat = cairo.LinearGradient(0.0, 0.0, 0.0, 1.0)
pat.add_color_stop_rgba(
0,
cairo_color.red,
cairo_color.green,
cairo_color.blue,
0
)
pat.add_color_stop_rgba(
1,
cairo_color.red,
cairo_color.green,
cairo_color.blue,
1
)
ctx.rectangle(0, 0, 1, 1)
ctx.set_source(pat)
ctx.fill()
surface.write_to_png('vertical_strip.png')
def vertical_white(width=10, height=100, subtlety=0.1):
"""
Draws a subtle vertical gradient strip: white with varying alpha.
"""
start = 0.5 - subtlety
end = 0.5 + subtlety
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
ctx = cairo.Context(surface)
ctx.scale(width/1.0, height/1.0)
pat = cairo.LinearGradient(0.0, 0.0, 0.0, 1.0)
pat.add_color_stop_rgba(0, 1, 1, 1, start)
pat.add_color_stop_rgba(1, 1, 1, 1, end)
ctx.rectangle(0, 0, 1, 1)
ctx.set_source(pat)
ctx.fill()
surface.write_to_png('vertical_white.png')