Function composite_arithmetic

pub fn composite_arithmetic(
    surface1: &SharedImageSurface,
    surface2: &SharedImageSurface,
    output_surface: &mut ExclusiveImageSurface,
    bounds: IRect,
    k1: f64,
    k2: f64,
    k3: f64,
    k4: f64,
)

Performs the arithmetic composite operation. Public for benchmarking.