Function evaluate_rows 

pub fn evaluate_rows(
    image: &Image,
    consume: impl FnMut(u32, &[u8]) -> Result<()>,
) -> Result<()>

Evaluate image and hand each output row, top to bottom, to consume.

This is the shape a sink pulls in: rows in order, so an encoder can write incrementally. In M1 the rows come from an already-materialized buffer; in M2 they arrive as the scheduler completes strips, and the consumer does not change.

Errors

Propagates evaluation errors, and any error consume returns.