A nice image

somegraph.go

package main

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

const (
	size      = 1000
	fileName  = "somegraph.png"
	maxColors = 255
	leftX     = -5.0
	rightX    = 5.0
	topY      = 3.0
	bottomY   = -3.0
)

var (
	wg sync.WaitGroup
)

func makePalette() []color.Color {
	palette := make([]color.Color, maxColors)

	for i := 0; i < maxColors-1; i++ {
		palette[i] = color.RGBA{uint8(i % 90), uint8(i % 90), uint8(i), maxColors}
	}

	palette[maxColors-1] = palette[0]

	return palette
}

func plotLine(img *image.Paletted, x int, convertedX, convertedY, factorY float64) {
	defer wg.Done()

	for y := 0; y < size; y++ {
		value := math.Pow(math.Pi * convertedX * math.Cos(convertedX * convertedY), 2)
		paletteIndex := uint8(value) % maxColors
		img.SetColorIndex(x, y, paletteIndex)

		convertedY += factorY
	}
}

func writeToFile(img *image.Paletted) {
	f, createErr := os.Create(fileName)
	if createErr != nil {
		panic(createErr)
	}

	defer f.Close()

	encodeErr := png.Encode(f, img)
	if encodeErr != nil {
		panic(encodeErr)
	}
}

func main() {
	palette := makePalette()
	rect := image.Rect(0, 0, size, size)
	img := image.NewPaletted(rect, palette)

	factorX := (rightX - leftX) / float64(size)
	factorY := (topY - bottomY) / float64(size)

	convertedX := leftX

	for x := 0; x < size; x++ {
		convertedY := bottomY

		wg.Add(1)
		go plotLine(img, x, convertedX, convertedY, factorY)

		convertedX += factorX
	}

	wg.Wait()
	writeToFile(img)
}