public void Begin () {
defaultBlendState = premultipliedAlpha ? BlendState.AlphaBlend : BlendState.NonPremultiplied;
device.RasterizerState = rasterizerState;
device.BlendState = defaultBlendState;
effect.Projection = Matrix.CreateOrthographicOffCenter(0, device.Viewport.Width, device.Viewport.Height, 0, 1, 0);
}