Golang golang-image3 (snippet)

Go programming example 'golang-image3'

golang-image3

Golang beginners example: golang-image3

// based on https://github.com/SimonWaldherr/bbmandelbrotGo
package main

import (
    "image"
    "image/color"
    "image/png"
    "log"
    "math"
    "os"
    "sync"
)

const (
    maxiteration = 192
)

var (
    zh float64
    zv float64
)

func init() {
    zh = 2.4
    zv = 2.4
}

func abs(z complex128) float64 {
    return math.Hypot(real(z), imag(z))
}

func mandel(c complex128) float64 {
    z := complex128(0)
    for i := 0; i < maxiteration; i++ {
        if abs(z) > 2 {
            return float64(i-1) / maxiteration
        }
        z = z*z + c
    }
    return 0
}

func pixelColor(x, y, width, height uint64, csr, csg, csb int) color.RGBA {
    xf := float64(x)/float64(width)*zv - (zv/2.0 + 0.5)
    yf := float64(y)/float64(height)*zh - (zh / 2.0)
    c := complex(xf, yf)
    calcval := int(mandel(c) * 255)

    return color.RGBA{
        uint8(int(csr) * calcval % 255),
        uint8(int(csg) * calcval % 255),
        uint8(int(csb) * calcval % 255),
        255,
    }
}

// Mandelbrot generates the Mandelbrot picture as *image.RGBA according to the parameters
func Mandelbrot(width, height, cx1, cx2, cy1, cy2 uint64, csr, csg, csb int) (*image.RGBA, string) {
    var wg sync.WaitGroup
    var fullHeight bool

    background := image.Rect(0, 0, int(cx2-cx1), int(cy2-cy1))
    img := image.NewRGBA(background)

    if height == cy2 && cy1 == 0 {
        fullHeight = true
        cy2 = cy2 / 2
    }

    for x := cx1; x < cx2; x++ {
        wg.Add(1)
        go func(x uint64) {
            defer wg.Done()
            if fullHeight {
                for y := cy1; y < cy2+1; y++ {
                    colval := pixelColor(x, y, width, height, csr, csg, csb)
                    img.Set(int(x)-int(cx1), int(y), colval)
                    img.Set(int(x)-int(cx1), int(height)-int(y), colval)
                }
            } else {
                for y := cy1; y < cy2; y++ {
                    colval := pixelColor(x, y, width, height, csr, csg, csb)
                    img.Set(int(x)-int(cx1), int(y)-int(cy1), colval)
                }
            }
        }(x)
    }

    wg.Wait()

    return img, ""
}

func main() {
    img, _ := Mandelbrot(900, 900, 0, 900, 0, 900, 2, 3, 1)

    file, err := os.OpenFile("./images/mandelbrot.png", os.O_WRONLY|os.O_CREATE, 0600)
    defer file.Close()

    if err != nil {
        log.Fatalf("Error opening file: %s\n", err)
    }

    err = png.Encode(file, img)
    if err != nil {
        log.Fatalf("Error encoding image: %s\n", err)
    }
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org