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#!/usr/bin/env python
"""Based on gtk+/test/testcairo.c
"""
from __future__ import division
import math
import sys
import cairo
import gtk
def oval_path(ctx, xc, yc, xr, yr):
ctx.save()
ctx.translate (xc, yc)
ctx.scale (1.0, yr / xr)
ctx.move_to (xr, 0.0)
ctx.arc (0, 0, xr, 0, 2 * math.pi)
ctx.close_path ()
ctx.restore()
def fill_checks(ctx, x, y, width, height):
CHECK_SIZE = 32
ctx.rectangle (x, y, width, height)
ctx.set_source_rgb (0.4, 0.4, 0.4)
ctx.fill ()
# Only works for CHECK_SIZE a power of 2
for j in range (x & -CHECK_SIZE, height, CHECK_SIZE):
for i in range (y & -CHECK_SIZE, width, CHECK_SIZE):
if ((i / CHECK_SIZE + j / CHECK_SIZE) % 2 == 0):
ctx.rectangle (i, j, CHECK_SIZE, CHECK_SIZE)
ctx.set_source_rgb (0.7, 0.7, 0.7)
ctx.fill ()
def draw_3circles(ctx, xc, yc, radius, alpha):
subradius = radius * (2 / 3. - 0.1)
ctx.set_source_rgba(1, 0, 0, alpha)
oval_path(ctx,
xc + radius / 3. * math.cos(math.pi * 0.5),
yc - radius / 3. * math.sin(math.pi * 0.5),
subradius, subradius)
ctx.fill()
ctx.set_source_rgba(0, 1, 0, alpha)
oval_path(ctx,
xc + radius / 3. * math.cos(math.pi * (0.5 + 2/.3)),
yc - radius / 3. * math.sin(math.pi * (0.5 + 2/.3)),
subradius, subradius)
ctx.fill()
ctx.set_source_rgba(0, 0, 1, alpha)
oval_path(ctx,
xc + radius / 3. * math.cos(math.pi * (0.5 + 4/.3)),
yc - radius / 3. * math.sin(math.pi * (0.5 + 4/.3)),
subradius, subradius)
ctx.fill()
def draw (ctx, width, height):
radius = 0.5 * min(width, height) - 10
xc = width / 2.
yc = height / 2.
target = ctx.get_target()
overlay = target.create_similar(cairo.CONTENT_COLOR_ALPHA, width, height)
punch = target.create_similar(cairo.CONTENT_ALPHA, width, height)
circles = target.create_similar(cairo.CONTENT_COLOR_ALPHA, width, height)
fill_checks(ctx, 0, 0, width, height)
# Draw a black circle on the overlay
overlay_cr = cairo.Context (overlay)
overlay_cr.set_source_rgb (0, 0, 0)
oval_path (overlay_cr, xc, yc, radius, radius)
overlay_cr.fill()
# Draw 3 circles to the punch surface, then cut
# that out of the main circle in the overlay
punch_cr = cairo.Context (punch)
draw_3circles (punch_cr, xc, yc, radius, 1.0)
overlay_cr.set_operator (cairo.OPERATOR_DEST_OUT)
overlay_cr.set_source_surface (punch, 0, 0)
overlay_cr.paint()
# Now draw the 3 circles in a subgroup again
# at half intensity, and use OperatorAdd to join up
# without seams.
circles_cr = cairo.Context (circles)
circles_cr.set_operator (cairo.OPERATOR_OVER)
draw_3circles (circles_cr, xc, yc, radius, 0.5)
overlay_cr.set_operator (cairo.OPERATOR_ADD)
overlay_cr.set_source_surface (circles, 0, 0)
overlay_cr.paint()
ctx.set_source_surface (overlay, 0, 0)
ctx.paint()
def expose(drawingarea, event):
ctx = drawingarea.window.cairo_create()
_, _, width, height = drawingarea.allocation
draw (ctx, width, height)
return False
def main():
win = gtk.Window()
win.connect('destroy', gtk.main_quit)
win.set_title('Knockout Groups')
win.set_default_size(400, 400)
drawingarea = gtk.DrawingArea()
win.add(drawingarea)
drawingarea.connect('expose_event', expose)
win.show_all()
gtk.main()
if __name__ == '__main__':
main()
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