Bitmap Replace Color

# Bitmap Replace Color
# @author  : Gabriel "Gab!" Teles
# @date    : 2014/07/30
# @website : http://www.mundorpgmaker.com.br/

class Bitmap
  MemcpyPL = Win32API.new('msvcrt', 'memcpy', 'pll', 'v')
  MemcpyLP = Win32API.new('msvcrt', 'memcpy', 'lpl', 'v')

  def address
    ptr = [0].pack('L')
    MemcpyPL.call(ptr, object_id * 2 + 16, 4)
    MemcpyPL.call(ptr, ptr.unpack('L').first + 8, 4)
    MemcpyPL.call(ptr, ptr.unpack('L').first + 16, 4)
    return ptr.unpack('L').first
  end

  def getRawData
    buf = 0.chr * (width * height * 4)
    Bitmap::MemcpyPL.call(buf, address, buf.size)
    return buf
  end

  def setRawData(buf)
    raise(RuntimeError, "Tamanho Incorreto") if (buf.size != (width * height * 4))
    Bitmap::MemcpyLP.call(address, buf, buf.size)
  end

  def replaceColor(fC, tC)
    data = getRawData
    offset = 0

    f = [fC.blue, fC.green, fC.red, fC.alpha].pack('C4')
    t = [tC.blue, tC.green, tC.red, tC.alpha].pack('C4')

    (width * height).times{
      data[offset, 4] = t if data[offset, 4] == f
      offset += 4
    }

    setRawData(data)
  end
end

x = Bitmap.new(100, 100)
x.fill_rect(0, 0, 50, 50, Color.new(255, 0, 0))
x.fill_rect(50, 0, 50, 50, Color.new(0, 255, 0))
x.fill_rect(0, 50, 50, 50, Color.new(0, 0, 255))
x.fill_rect(50, 50, 50, 50, Color.new(255, 0, 255))
x.replaceColor(Color.new(255, 0, 0), Color.new(255, 255, 0))

y = Sprite.new
y.bitmap = x

loop { Graphics.update }