Function sobel_3x3_u8 

pub fn sobel_3x3_u8(
    input: ImageView<'_, u8, 1>,
    dx: usize,
    dy: usize,
    scale: f64,
    delta: f64,
    border: BorderMode<u8, 1>,
) -> VisionResult<Image<f32, 1>>

Computes a first-order 3x3 Sobel derivative directly into signed f32 output.

This specialization accepts grayscale u8 input, derivative order (1, 0) or (0, 1), and Replicate or Reflect101 borders. It avoids the generic separable filter’s full-image f64 intermediate while preserving the same coefficients, scale, delta, metadata, and strided-input behavior.