go_lang_pics.go

// https://tour.golang.org/moretypes/18
// https://www.benjoffe.com/code/tools/functions3d/examples
// https://www.physicsforums.com/threads/cool-3-d-functions-for-graphing.140087/

package main

import (
	"golang.org/x/tour/pic"
	"fmt"
	"math"
)

func f1(x, y int) int {
	return (x + y)/2
}

func f2(x, y int) int {
	return x * y
}

func f3(x, y int) int {
	return x ^ y
}

func f4(x, y int) int {
	return x & y
}

func f5(x, y int) int {
	return x << (uint(y) % 8)
}

func f6(x, y int) int {
	return x >> (uint(y) % 8)
}

func dist(x1, y1, x2, y2 float64) float64 {
	dx2 := math.Pow(x1 - x2, 2)
	dy2 := math.Pow(y1 - y2, 2)
	return math.Sqrt(dx2 + dy2)
}

func f7(x, y int) int {
	xf, yf := float64(x), float64(y)
	cx, cy := float64(w/2), float64(h/2)
	return int(dist(xf, yf, cx, cy))
}

func f8(x, y int) int {
	xf := float64(x)
	yf := float64(y)
	x2 := wf * math.Sin(xf)
	y2 := hf * math.Cos(yf)
	return int(dist(xf, yf, x2, y2))
}

func f9(x, y int) int {
	xf := float64(x)
	yf := float64(y)
	x2 := xf * xf
	y2 := yf * xf - yf
	return int(dist(xf, yf, x2, y2))
}

func SimplePic(dx, dy int) (res [][]uint8) {
	w, h = dx, dy
	wf, hf = float64(w), float64(h)
	res = make([][]uint8, dy)
	for y := 0; y < dy; y++ {
		res[y] = make([]uint8, dx)
		for x := 0; x < dx; x++ {
			res[y][x] = uint8 (f(int(x), int(y)))
		}
	}
	return
}

func z1(x, y float64) float64 {
	xmin, xmax = -5, 5
	ymin, ymax = -5, 5
	return x + y
}


func z2(x, y float64) float64 {
	const a = 1
	xmin, xmax = -a, a
	ymin, ymax = -a, a
	return math.Sin(5*x)*math.Cos(5*y)/5
}

func z3(x, y float64) float64 {
	const a = 1
	xmin, xmax = -a, a
	ymin, ymax = -a, a
	return 1-math.Abs(x+y)-math.Abs(y-x)
}

func sign(x float64) float64 {
	if x < 0 {
		return -1
	} else if x > 0 {
		return 1
	}
	return 0
}

func z4(x, y float64) float64 {
	const a = 1
	xmin, xmax = -a, a
	ymin, ymax = -a, a
	return sign(x - y)
}

func z5(x, y float64) float64 {
	const a = 2
	xmin, xmax = -a, a
	ymin, ymax = -a, a
	return .75/math.Exp(math.Pow(x*5,2)*math.Pow(y*5,2))
}

var z = z5

func HeightMapPic(dx, dy int) (res [][]uint8) {
	w, h = dx, dy
	wf, hf = float64(w), float64(h)
	mat := make([][]float64, dy)
	minVal := math.Inf(1)
	maxVal := math.Inf(-1)
	_ = z(0, 0)
	for y := 0; y < dy; y++ {
		mat[y] = make([]float64, dx)
		for x := 0; x < dx; x++ {
			xf, yf := float64(x), float64(y)
			xf = xmin + xf/wf * (xmax - xmin)
			yf = ymin + yf/wf * (ymax - ymin)
			zval := z(xf, yf)
			mat[y][x] = zval
			minVal = math.Min(minVal, zval)
			maxVal = math.Max(maxVal, zval)
		}
	}
	if false { fmt.Println(minVal, maxVal) }
	M := maxVal - minVal
	for y := 0; y < dy; y++ {
		for x := 0; x < dx; x++ {
			mat[y][x] -= minVal
			mat[y][x] /= M
			if true && false && y == 0 {
				fmt.Println(mat[y][x])
			}
		}
	}
	res = make([][]uint8, dy)
	for y := 0; y < dy; y++ {
		res[y] = make([]uint8, dx)
		for x := 0; x < dx; x++ {
			res[y][x] = uint8(255 * mat[y][x])
		}
	}
	return
}

var f = f9
// var z = z2
var w, h int
var wf, hf float64
var xmin, xmax float64
var ymin, ymax float64

func main() {
	if 0 == 1 { fmt.Println(math.Inf(-1) < 2) }
	pic.Show(HeightMapPic)
}