Function assert_image_snapshot_with_tolerance 

pub fn assert_image_snapshot_with_tolerance(
    snapshot: Snapshot,
    rgba: &[u8],
    width: u32,
    height: u32,
    tolerance: Tolerance,
)

Available on crate feature snapshot only.

Assert that rgba matches snapshot within tolerance.

Like assert_image_snapshot, a missing snapshot is written rather than failed on — natively, where there is somewhere to write it. A freshly written snapshot is not judged at all, since it was just made from this frame.

A frame that does not match is kept before the assertion fails, so a run that fails in CI leaves it behind for the job to upload: natively it is written under DEFAULT_MISMATCH_DIR (or MISMATCH_DIR_ENV), and on the web it is handed to the test runner, which is the process that has a filesystem. Keeping it is a courtesy to whoever reads the result, so a failure to do so is reported and dropped rather than replacing the mismatch it was meant to explain.