構造をNanoVG的に変更

orevg.rb

require 'dxruby'

# ラスタライズ結果を見やすく描画する
module Viewer
  def self.draw(image, triangles)
    s = 400.0 / image.width
    Window.mag_filter = TEXF_POINT
    Window.draw_ex(50, 50, image, scale_x:s, scale_y:s, center_x:0, center_y:0)
    image.width.times do |c|
      Window.draw_line(c * s + 50, 50, c * s + 50, image.width * s + 50, [100, 100, 100])
      Window.draw_line(50, c * s + 50, image.width * s + 50, c * s + 50, [100, 100, 100])
    end
    
    triangles.each do |ary|
      x1, y1, x2, y2, x3, y3 = *ary
      Window.draw_line(x1 * s + 50, y1 * s + 50, x2 * s + 50, y2 * s + 50, C_RED)
      Window.draw_line(x2 * s + 50, y2 * s + 50, x3 * s + 50, y3 * s + 50, C_RED)
      Window.draw_line(x3 * s + 50, y3 * s + 50, x1 * s + 50, y1 * s + 50, C_RED)
    end
  end
end

class OreVG
  attr_accessor :image, :triangles

  class MoveTo < Struct.new(:x, :y);end
  class LineTo < Struct.new(:x, :y);end
  class Point < Struct.new(:x, :y);end

  def initialize(l)
    @image = Image.new(l, l, C_WHITE)
    @triangles = []
    @commands = []
    @width = 1
    @points = []
  end

  # EdgeFunction
  # E(x, y) = (x - X) * dy - (y - Y) * dx
  # E(x, y) <= 0で中と判定。3つのエッジの内側であれば塗る。
  private def rasterize(x1, y1, x2, y2, x3, y3)
    dx12 = x2 - x1
    dy12 = y2 - y1
    dx23 = x3 - x2
    dy23 = y3 - y2
    dx31 = x1 - x3
    dy31 = y1 - y3

    # 基点。ピクセルの中心で計算する。
    e1 = (0.5 - x1) * dy12 - (0.5 - y1) * dx12
    e2 = (0.5 - x2) * dy23 - (0.5 - y2) * dx23
    e3 = (0.5 - x3) * dy31 - (0.5 - y3) * dx31

    @image.height.times do |y|
      et1 = e1
      et2 = e2
      et3 = e3
      @image.width.times do |x|
        yield x, y if et1 <= 0 and et2 <= 0 and et3 <= 0
        et1 += dy12
        et2 += dy23
        et3 += dy31
      end
      e1 -= dx12
      e2 -= dx23
      e3 -= dx31
    end
  end

  private def triangle(x1, y1, x2, y2, x3, y3)
    rasterize(x1, y1, x2, y2, x3, y3) do |x, y|
      @image[x,y] = [100, 100, 255]
    end
    @triangles << [x1, y1, x2, y2, x3, y3]
  end

  private def line(x1, y1, x2, y2)
    dx = x2 - x1
    dy = y2 - y1
    len = Math.sqrt(dx * dx + dy * dy)
    dmx = dx / len
    dmy = dy / len
    w = @width * 0.5

    tx1 = x1 + dmy * w
    ty1 = y1 - dmx * w
    tx2 = x1 - dmy * w
    ty2 = y1 + dmx * w
    tx3 = x2 + dmy * w
    ty3 = y2 - dmx * w
    tx4 = x2 - dmy * w
    ty4 = y2 + dmx * w
    triangle(tx1, ty1, tx3, ty3, tx2, ty2)
    triangle(tx2, ty2, tx3, ty3, tx4, ty4)
  end

  private def append_commands(cmd)
    @commands << cmd
  end

  private def flatten_paths
    @commands.each do |cmd|
      case cmd
      when MoveTo
        @points << Point.new(cmd.x, cmd.y)
      when LineTo
        @points << Point.new(cmd.x, cmd.y)
      end
    end
  end

  def move_to(x, y)
    append_commands(MoveTo.new(x, y))
  end

  def line_to(x, y)
    append_commands(LineTo.new(x, y))
  end

  def width=(w)
    @width = w
  end

  def stroke
    flatten_paths
    
    @points.each_cons(2) do |p1, p2|
      line(p1.x, p1.y, p2.x, p2.y)
    end
  end
end

vg = OreVG.new(50)
vg.move_to(2, 5)
vg.line_to(42, 25)
vg.line_to(22, 40)
vg.width = 10
vg.stroke
Window.loop do
  Viewer.draw(vg.image, vg.triangles)
end