# File lib/png.rb, line 482 def extract x0, y0, x1, y1 canvas = Canvas.new(x1-x0+1, y1-y0+1) (x0..x1).each_with_index do |x2, x3| (y0..y1).each_with_index do |y2, y3| canvas[x3, y3] = self[x2, y2] end end canvas end