go get -u github.com/matsuyoshi30/song2

package main

import (
    "fmt"
    "image"
    "image/png"
    "os"

    "github.com/matsuyoshi30/song2"
)

func main() {
    img, err := os.Open("./input.png")
    if err != nil {
        fmt.Println(err)
        return
    }

    img, _, err := image.Decode(file)
    if err != nil {
        fmt.Println(err)
        return
    }

    blured := song2.GaussianBlur(img, 3.0)

    out, err := os.Create("./output.png")
    if err != nil {
        fmt.Println(err)
        return
	}

    if err := png.Encode(out, blured); err != nil {
        fmt.Println(err)
        return
    }
}

git clone https://github.com/matsuyoshi30/song2
cd song2/cmd/song2 && go install

Usage:
  song2 [FLAGS] [FILE]

FLAGS:
  -o  Write output image to specifig filepath [default: blured.png]
  -r  Radius [default: 3.0]

Author:
  matsuyoshi30 <[email protected]>

% go test -bench . -benchmem
goos: darwin
goarch: amd64
pkg: github.com/matsuyoshi30/song2
cpu: Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz
BenchmarkGaussianBlurAnotherAlgorithm1-4   	       1	10073325776 ns/op	 3145888 B/op	  262148 allocs/op
BenchmarkGaussianBlurAnotherAlgorithm2-4   	       1	1365498035 ns/op	 5243088 B/op	  786440 allocs/op
BenchmarkGaussianBlurAnotherAlgorithm3-4   	       4	 318496693 ns/op	11534604 B/op	 2359301 allocs/op
BenchmarkGaussianBlur-4                    	      51	  24086941 ns/op	 2097965 B/op	      12 allocs/op
BenchmarkStackblur-4                       	      48	  24818379 ns/op	 3146072 B/op	  524301 allocs/op
BenchmarkBildBlur-4                        	      30	  37115297 ns/op	 4244496 B/op	      21 allocs/op