Go language learning exercises.
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// Copyright 2018 Gytis Repečka. All rights reserved.
// Use of this source code is governed by a GNU GPL
// license that can be found in the LICENSE file.
package main
import (
"fmt"
"os"
"image"
"image/color"
"image/png"
"image/draw"
)
type Circle struct {
imageToDraw draw.Image
x, y, r int
c color.Color
}
// https://en.wikipedia.org/wiki/Midpoint_circle_algorithm
func (circle *Circle) Draw() {
x := circle.r - 1
y := 0
dx := 1
dy := 1
err := dx - (circle.r * 2)
for x > y {
circle.imageToDraw.Set(circle.x + x, circle.y + y, circle.c)
circle.imageToDraw.Set(circle.x + y, circle.y + x, circle.c)
circle.imageToDraw.Set(circle.x - y, circle.y + x, circle.c)
circle.imageToDraw.Set(circle.x - x, circle.y + y, circle.c)
circle.imageToDraw.Set(circle.x - x, circle.y - y, circle.c)
circle.imageToDraw.Set(circle.x - y, circle.y - x, circle.c)
circle.imageToDraw.Set(circle.x + y, circle.y - x, circle.c)
circle.imageToDraw.Set(circle.x + x, circle.y - y, circle.c)
if err <= 0 {
y++
err += dy
dy += 2
}
if err > 0 {
x--
dx += 2
err += dx - (circle.r * 2)
}
}
}
func main() {
outFileName := "draw-image.png"
// Create 400x300 image
imageToDraw := image.NewRGBA(image.Rect(0, 0, 400, 300))
var myCircle Circle
for r := 130; 0 < r; r-- {
myCircle = Circle{imageToDraw, 200, 150, r, color.RGBA{0, 200, 0, 255}}
myCircle.Draw()
}
f, errf := os.OpenFile(outFileName, os.O_WRONLY|os.O_CREATE, 0600)
if errf != nil {
fmt.Println(errf)
return
}
defer f.Close()
png.Encode(f, imageToDraw)
fmt.Printf("Image written: %s\n", outFileName)
}