MAX_OUTPUT_DIM = 2048
MAX_OUTPUT_DIM_FAST = 1024


def max_dim_for_mode(mode): return MAX_OUTPUT_DIM_FAST if mode == "fast" else MAX_OUTPUT_DIM


def compute_output_dimensions(w, h, max_dim=MAX_OUTPUT_DIM):
    # Pin the long side to max_dim and scale the short side proportionally.
    # We snap to the nearest multiple of 8 (not floor) to minimise aspect ratio
    # distortion: floor always undershoots, whereas rounding keeps the error
    # within ±4px, which halves the worst-case ratio deviation.
    if w > h:
        nw = max_dim
        nh = round(nw * h / w / 8) * 8
    else:
        nh = max_dim
        nw = round(nh * w / h / 8) * 8
    return nw, nh