Make rounded images in Golang

# Rounded Image - Golang

Make rounded images in Golang

circle.go

package main

import (
	"image"
	"image/color"
	"image/draw"
)

type circle struct {
	p image.Point
	r int
}

func (c *circle) ColorModel() color.Model {
	return color.AlphaModel
}

func (c *circle) Bounds() image.Rectangle {
	return image.Rect(c.p.X-c.r, c.p.Y-c.r, c.p.X+c.r, c.p.Y+c.r)
}

func (c *circle) At(x, y int) color.Color {
	xx, yy, rr := float64(x-c.p.X)+0.5, float64(y-c.p.Y)+0.5, float64(c.r)
	if xx*xx+yy*yy < rr*rr {
		return color.Alpha{A: 255}
	}
	return color.Alpha{}
}

// RoundImage creates a new rounded image from source
func RoundImage(source image.Image) image.Image {
	b := source.Bounds()
	var radius int
	if b.Max.X <= b.Max.Y {
		radius = b.Max.X / 2
	} else {
		radius = b.Max.Y / 2
	}
	c := &circle{
		p: image.Point{X: b.Dx() / 2, Y: b.Dy() / 2},
		r: radius,
	}
	result := image.NewRGBA(c.Bounds())

	var ZP image.Point
	draw.DrawMask(result, source.Bounds(), source, ZP, c, ZP, draw.Over)

	return result
}

main.go

package main

import (
	"image"
	"image/png"
	"log"
	"os"
)

func loadPng(name string) (image.Image, string, error) {
	img, err := os.Open(name)
	if err != nil {
		return nil, "", err
	}
	defer img.Close()

	return image.Decode(img)
}

func main() {
	source, _, err := loadPng("path/to/my/image.png")
	if err != nil {
		log.Fatal(err.Error())
	}

	rounded := RoundImage(source)

	outputFile, err := os.Create("rounded.png")
	if err != nil {
		log.Fatal(err.Error())
	}
	defer outputFile.Close()

	png.Encode(outputFile, rounded)
}