pub fn blur<I: GenericImageView>(
    image: &I,
    sigma: f32,
) -> ImageBuffer<I::Pixel, Vec<<I::Pixel as Pixel>::Subpixel>>where
    I::Pixel: 'static,Expand description
Image sampling
Performs a Gaussian blur on the supplied image.
sigma is a measure of how much to blur by.
Use crate::imageops::fast_blur() for a faster but less
accurate version.
This method assumes alpha pre-multiplication for images that contain non-constant alpha.