public function setPixel($x, $y, $value = true, $color = null)
{
$y = (int) $y;
$x = (int) $x;
if ($x < $this->width && $y < $this->height) {
$this->matrix[$x + $y * $this->width] = !!$value;
$this->colors[$x >> 1 + ($y >> 2) * $this->width] = $color;
}
}