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