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-- Demonstrate the effect of different fill rules. Two stars are filled,
-- both with exactly the same path commands but a different fill rule.
local Cairo = require "oocairo"
local RADIUS, NUM_POINTS, MARGIN = 100, 5, 5
local IMG_WD, IMG_HT = RADIUS * 4 + MARGIN * 3, RADIUS * 2 + MARGIN * 2
local PI = math.asin(1) * 2
local surface = Cairo.image_surface_create("rgb24", IMG_WD, IMG_HT)
local cr = Cairo.context_create(surface)
-- White background.
cr:set_source_rgb(1, 1, 1)
cr:paint()
local function draw_star (x, y)
local ang_step = (2 * PI) / NUM_POINTS
cr:move_to(x + RADIUS, y)
local ang = 2 * ang_step
for _ = 1, NUM_POINTS - 1 do
cr:line_to(x + RADIUS * math.cos(ang), y + RADIUS * math.sin(ang))
ang = ang + 2 * ang_step
end
cr:close_path()
cr:set_source_rgb(.5, .5, .5)
cr:fill_preserve()
cr:set_source_rgb(.3, 0, 0)
cr:stroke()
end
cr:set_fill_rule("winding") -- this is the default anyway
draw_star(MARGIN + RADIUS, MARGIN + RADIUS)
cr:set_fill_rule("even-odd")
draw_star(2 * MARGIN + 3 * RADIUS, MARGIN + RADIUS)
surface:write_to_png("fill-rule.png")
-- vi:ts=4 sw=4 expandtab
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