Function heif_image_get_width 

pub unsafe extern "C" fn heif_image_get_width(
    img: *const heif_image,
    channel: heif_channel,
) -> c_int

Get the width of a specified image channel.

@param img the image to get the width for @param channel the channel to select @return the width of the channel in pixels, or -1 the channel does not exist in the image