Area of a polygon with integer coordinates is $${\color{#359BE1}S} = {\color{#40b521}N_1} /2 + {\color{#E64D15}N_2} — 1,$$ where ${\color{#40b521}N_1}$ — the number of integer points on the polygon's boundary, and ${\color{#E64D15}N_2}$ — number of integer points that are interior to the polygon.