Function decode_into 

pub fn decode_into(
    pixels: &mut [u8],
    blurhash: &str,
    width: u32,
    height: u32,
    punch: f32,
) -> Result<(), Error>

Decodes the given blurhash to an image of the specified size into an existing buffer.

The punch parameter can be used to de- or increase the contrast of the resulting image.