From 82312a9d246ece00684edd286e7ce65ff7090a21 Mon Sep 17 00:00:00 2001
From: Steven Polley <spolley@nextdigital.ca>
Date: Tue, 31 Jul 2018 16:21:41 -0600
Subject: [PATCH] Added colors to web

---
 web/render.go | 87 +++++++++++++++++++++++++++++++++++++++++++++++++--
 web/web.go    |  2 +-
 2 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/web/render.go b/web/render.go
index 54eddba..b38992e 100644
--- a/web/render.go
+++ b/web/render.go
@@ -1,16 +1,20 @@
 package main
 
 import (
+	"fmt"
 	"image"
 	"image/color"
 	"image/png"
 	"log"
+	"math"
 	"math/cmplx"
 	"net/http"
 	"runtime"
 	"strconv"
 	"strings"
 	"sync"
+
+	"deadbeef.codes/steven/mandelbrot/palette"
 )
 
 const (
@@ -19,6 +23,10 @@ const (
 	Brighten   = 1024
 )
 
+var (
+	colors []color.RGBA
+)
+
 func mandelbrot(c complex128) uint16 {
 	var z complex128
 
@@ -33,7 +41,7 @@ func mandelbrot(c complex128) uint16 {
 }
 
 type pixel struct {
-	out          *image.Gray16
+	out          *image.RGBA
 	x, y         int
 	tileX, tileY int64
 	tileZoom     uint8
@@ -50,8 +58,8 @@ func computeThread() {
 				(float64(p.y)/Size+float64(p.tileY))/float64(uint(1<<p.tileZoom)),
 			),
 		)
-		p.out.SetGray16(p.x, p.y, color.Gray16{val * Brighten})
 
+		p.out.SetRGBA(p.x, p.y, colors[val])
 		p.wg.Done()
 	}
 }
@@ -63,6 +71,10 @@ func main() {
 		go computeThread()
 	}
 
+	colorStep := float64(256)
+	colors = interpolateColors("Plan9", colorStep)
+	fmt.Println(len(colors))
+
 	log.Fatal(http.ListenAndServe(":6161", nil))
 }
 
@@ -95,7 +107,7 @@ func renderTile(w http.ResponseWriter, r *http.Request) {
 
 	wg.Add(Size * Size)
 
-	img := image.NewGray16(image.Rect(0, 0, Size, Size))
+	img := image.NewRGBA(image.Rect(0, 0, Size, Size))
 
 	for x := 0; x < Size; x++ {
 		for y := 0; y < Size; y++ {
@@ -112,3 +124,72 @@ func renderTile(w http.ResponseWriter, r *http.Request) {
 func init() {
 	http.HandleFunc("/mandelbrot/", renderTile)
 }
+
+func interpolateColors(paletteCode string, numberOfColors float64) []color.RGBA {
+	var factor float64
+	steps := []float64{}
+	cols := []uint32{}
+	interpolated := []uint32{}
+	interpolatedColors := []color.RGBA{}
+
+	for _, v := range palette.ColorPalettes {
+		factor = 1.0 / numberOfColors
+		switch v.Keyword {
+		case paletteCode:
+			if paletteCode != "" {
+				for index, col := range v.Colors {
+					if col.Step == 0.0 && index != 0 {
+						stepRatio := float64(index+1) / float64(len(v.Colors))
+						step := float64(int(stepRatio*100)) / 100 // truncate to 2 decimal precision
+						steps = append(steps, step)
+					} else {
+						steps = append(steps, col.Step)
+					}
+					r, g, b, a := col.Color.RGBA()
+					r /= 0xff
+					g /= 0xff
+					b /= 0xff
+					a /= 0xff
+					uintColor := uint32(r)<<24 | uint32(g)<<16 | uint32(b)<<8 | uint32(a)
+					cols = append(cols, uintColor)
+				}
+
+				var min, max, minColor, maxColor float64
+				if len(v.Colors) == len(steps) && len(v.Colors) == len(cols) {
+					for i := 0.0; i <= 1; i += factor {
+						for j := 0; j < len(v.Colors)-1; j++ {
+							if i >= steps[j] && i < steps[j+1] {
+								min = steps[j]
+								max = steps[j+1]
+								minColor = float64(cols[j])
+								maxColor = float64(cols[j+1])
+								uintColor := cosineInterpolation(maxColor, minColor, (i-min)/(max-min))
+								interpolated = append(interpolated, uint32(uintColor))
+							}
+						}
+					}
+				}
+
+				for _, pixelValue := range interpolated {
+					r := pixelValue >> 24 & 0xff
+					g := pixelValue >> 16 & 0xff
+					b := pixelValue >> 8 & 0xff
+					a := 0xff
+
+					interpolatedColors = append(interpolatedColors, color.RGBA{uint8(r), uint8(g), uint8(b), uint8(a)})
+				}
+			}
+		}
+	}
+
+	return interpolatedColors
+}
+
+func cosineInterpolation(c1, c2, mu float64) float64 {
+	mu2 := (1 - math.Cos(mu*math.Pi)) / 2.0
+	return c1*(1-mu2) + c2*mu2
+}
+
+func linearInterpolation(c1, c2, mu uint32) uint32 {
+	return c1*(1-mu) + c2*mu
+}
diff --git a/web/web.go b/web/web.go
index 3335121..9e03974 100644
--- a/web/web.go
+++ b/web/web.go
@@ -16,7 +16,7 @@ func init() {
 		fmt.Fprintf(w, `<!DOCTYPE html>
 <html>
 <head>
-<title>Mandelbrot Map</title>
+<title>MandelMapper</title>
 <script src="https://maps.googleapis.com/maps/api/js?sensor=false"></script>
 <script>
 var mandelbrotTypeOptions = {