77 lines
1.7 KiB
Go
77 lines
1.7 KiB
Go
// 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)
|
|
}
|