mandelbrot.go

package main

import (
	"fmt"
	"image"
	"image/color"
	"image/png"
	"math"
	"math/cmplx"
	"os"
	"sync"
)

var (
	maxEscape = 255
	//viewCenter = complex(-0.69955, 0.37999)
	viewCenter = complex(-0.77568377, 0.13646737)
	//viewCenter = complex(-0.75, 0.1)
	//viewCenter = complex(0.360240443437614363236125244449545308482607807958585750488375814740195346059218100311752936722773426396233731729724987737320035372683285317664532401218521579554288661726564324134702299962817029213329980895208036363104546639698106204384566555001322985619004717862781192694046362748742863016467354574422779443226982622356594130430232458472420816652623492974891730419252651127672782407292315574480207005828774566475024380960675386215814315654794021855269375824443853463117354448779647099224311848192893972572398662626725254769950976527431277402440752868498588785436705371093442460696090720654908973712759963732914849861213100695402602927267843779747314419332179148608587129105289166676461292845685734536033692577618496925170576714796693411776794742904333484665301628662532967079174729170714156810530598764525260869731233845987202037712637770582084286587072766838497865108477149114659838883818795374195150936369987302574377608649625020864292915913378927790344097552591919409137354459097560040374880346637533711271919419723135538377394364882968994646845930838049998854075817859391340445151448381853615103761584177161812057928,
	//	-0.6413130610648031748603750151793020665794949522823052595561775430644485741727536902556370230689681162370740565537072149790106973211105273740851993394803287437606238596262287731075999483940467161288840614581091294325709988992269165007394305732683208318834672366947550710920088501655704252385244481168836426277052232593412981472237968353661477793530336607247738951625817755401065045362273039788332245567345061665756708689359294516668271440525273653083717877701237756144214394870245598590883973716531691124286669552803640414068523325276808909040317617092683826521501539932397262012011082098721944643118695001226048977430038509470101715555439047884752058334804891389685530946112621573416582482926221804767466258346014417934356149837352092608891639072745930639364693513216719114523328990690069588676087923656657656023794484324797546024248328156586471662631008741349069961493817600100133439721557969263221185095951241491408756751582471307537382827924073746760884081704887902040036056611401378785952452105099242499241003208013460878442953408648178692353788153787229940221611731034405203519945313911627314900851851072122990492499999999999999999991,
	//)

	imgWidth  = 1000
	imgHeight = 1000
)

func main() {

	var wg sync.WaitGroup
	bMax := complex(2, 2)
	for zoom := 0; zoom < 10; zoom++ {
		wg.Add(1)
		fmt.Println("Starting goroutine with: ", bMax)
		go func(boundsMax complex128, index int, maxE int) {
			defer wg.Done()
			img := image.NewRGBA(image.Rect(0, 0, imgWidth, imgHeight))
			for x := 0; x <= imgWidth; x++ {
				for y := 0; y <= imgHeight; y++ {
					pos := transposePosition(x, y, boundsMax)
					escape := calculateEscape(pos, maxE)
					c := escapeColor(escape, maxE)
					img.Set(x, y, c)
				}
			}

			file, err := os.Create(fmt.Sprintf("progress/mandelbrot-%d.png", index))
			if err != nil {
				panic(err)
			}
			_ = png.Encode(file, img)
			file.Close()

			fmt.Println(index, ". zoom in done at: ", viewCenter+boundsMax, "with max escape: ", maxE)
		}(bMax, zoom, maxEscape)

		bMax = bMax * 0.1 // zoom
		maxEscape = int(float64(maxEscape) * (1.0 + (float64(zoom) / 100.0)))
	}
	wg.Wait()
}

func calculateEscape(pos complex128, maxE int) int {
	prevPos := complex(0, 0)
	for escape := 0; escape < maxE; escape++ {
		prevPos = cmplx.Pow(prevPos, 2) + pos
		r := real(prevPos)
		i := imag(prevPos)
		length := math.Sqrt(math.Pow(2, r) + math.Pow(2, i))
		if length > 2 {
			return escape
		}
	}
	return maxE
}

func escapeColor(escape int, maxE int) color.Color {
	escape = maxE - escape
	c := uint8((225.0/float64(maxE))*float64(escape)) + 30
	rgba := color.RGBA{R: c, G: c, B: c, A: 255}
	return rgba
}

func transposePosition(posX, posY int, boundsMax complex128) complex128 {
	x := float64(posX) / float64(imgWidth)
	y := float64(posY) / float64(imgHeight)

	xMin := real(viewCenter - boundsMax)
	xMax := real(viewCenter + boundsMax)
	xNew := math.Abs(xMin-xMax)*x + xMin

	yMin := imag(viewCenter - boundsMax)
	yMax := imag(viewCenter + boundsMax)
	yNew := math.Abs(yMin-yMax)*y + yMin

	return complex(xNew, yNew)
}