Gamemaker Axelay background script (test)

///draw_background_axelay(background, frame, x, y, scroll, width, height);
var _bg = argument[0];  //  sprite id
var _frame = argument[1];   //  frame number
var _x = argument[2];   //  x start location
var _y = argument[3];   //  y start location (horizon line)
var _scroll = argument[4];  //  scroll value (update every frame!)
var _width = argument[5];   //  x size (image scaled)
var _height = argument[6];  //  y size (scale based on y)

var _offset = -(_scroll % _height);
if(_offset < 0)
{
    _offset += _height;
}

for(var _i = 0; _i < _height; ++_i)
{
    var _scale = max(1.0, _i * (8 / _height));

    draw_sprite_part_ext(_bg, _frame, 0, _offset, _width, 1.0, _x, _y + _i, 1.0, _scale, c_white, 1.0);

    ++_offset;
    if(_offset >= _height)
    {
        _offset = 0;
    }

    _i += (_scale - 1.0);
}