cbezier1.rb

#! /usr/local/bin/ruby -w
require 'RMagick'

imgl = Magick::ImageList.new
imgl.new_image(390, 140, Magick::HatchFill.new('white','lightcyan2'))
gc = Magick::Draw.new

# Draw Bezier curve
gc.stroke('red')
gc.stroke_width(2)
gc.fill_opacity(0)
gc.bezier(20,120, 20,20, 320, 20, 320,120)

# Draw circles around endpoints
gc.fill_opacity(0)
gc.stroke('gray50').stroke_width(1)
gc.circle(20,120, 23, 123)
gc.circle(320,120, 323, 123)

# Draw filled circles around control points
gc.line(20,120, 20,20)
gc.line(320,120, 320,20)
gc.fill_opacity(1)
gc.fill('gray50')
gc.circle(20,20, 23,23)
gc.circle(320,20, 323,23)

# Annotate
gc.font_weight(Magick::NormalWeight)
gc.font_style(Magick::NormalStyle)
gc.fill('black')
gc.stroke('transparent')
gc.text(27,120, "'20,120'")
gc.text(27,20, "'20,20'")
gc.text(327,120, "'320,120'")
gc.text(327,20, "'320,20'")
gc.draw(imgl)

imgl.border!(1, 1, "lightcyan2")
imgl.write('cbezier1.gif')
exit(0)