From 6bb9f157c9274180f9a80eabb981fbb0416cd8a1 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <e.urbach@gmail.com>
Date: Wed, 11 Apr 2018 19:01:09 +0200
Subject: [PATCH] Experimental image manipulation tool

---
 .../improve-image-quality.go                  | 168 ++++++++++++++++++
 1 file changed, 168 insertions(+)
 create mode 100644 patches/improve-image-quality/improve-image-quality.go

diff --git a/patches/improve-image-quality/improve-image-quality.go b/patches/improve-image-quality/improve-image-quality.go
new file mode 100644
index 00000000..78365d20
--- /dev/null
+++ b/patches/improve-image-quality/improve-image-quality.go
@@ -0,0 +1,168 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/color"
+	_ "image/jpeg"
+	"image/png"
+	"io/ioutil"
+	"math"
+	"os"
+
+	"github.com/animenotifier/arn"
+)
+
+func main() {
+	data, err := ioutil.ReadFile("input.jpg")
+
+	if err != nil {
+		panic(err)
+	}
+
+	img, format, err := image.Decode(bytes.NewReader(data))
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(img.Bounds().Dx(), img.Bounds().Dy(), format)
+	improved := ImproveQuality(img)
+	f, err := os.Create("output.png")
+
+	if err != nil {
+		panic(err)
+	}
+
+	defer f.Close()
+	png.Encode(f, improved)
+}
+
+const max = float64(65535)
+
+// Pixel ...
+type Pixel struct {
+	X     int
+	Y     int
+	Color arn.HSLColor
+}
+
+// Area ...
+type Area struct {
+	AverageColor color.Color
+	Pixels       []Pixel
+}
+
+// Add ...
+func (area *Area) Add(x, y int, hsl arn.HSLColor) {
+	area.Pixels = append(area.Pixels, Pixel{
+		X:     x,
+		Y:     y,
+		Color: hsl,
+	})
+}
+
+const (
+	hueTolerance        = 0.1
+	lightnessTolerance  = 0.1
+	saturationTolerance = 0.1
+)
+
+// ImproveQuality returns the average color of an image in HSL format.
+func ImproveQuality(img image.Image) *image.NRGBA {
+	width := img.Bounds().Dx()
+	height := img.Bounds().Dy()
+	clone := image.NewNRGBA(image.Rect(0, 0, width, height))
+	hueAreas := []Area{}
+
+	for x := 0; x < width; x++ {
+		for y := 0; y < height; y++ {
+			color := img.At(x, y)
+			rUint, gUint, bUint, _ := color.RGBA()
+			r := float64(rUint) / max
+			g := float64(gUint) / max
+			b := float64(bUint) / max
+			h, s, l := arn.RGBToHSL(r, g, b)
+			areaIndex := -1
+
+			// Find similar area
+			for i := 0; i < len(hueAreas); i++ {
+				area := hueAreas[i]
+
+				// Is the pixel close to any pixel in the area we're checking?
+				for _, pixel := range area.Pixels {
+					xDist := x - pixel.X
+					yDist := y - pixel.Y
+
+					if xDist < 0 {
+						xDist = -xDist
+					}
+
+					if yDist < 0 {
+						yDist = -yDist
+					}
+
+					if xDist <= 1 && yDist <= 1 {
+						// Is the color similar?
+						if math.Abs(h-pixel.Color.Hue) <= hueTolerance && math.Abs(s-pixel.Color.Saturation) <= saturationTolerance && math.Abs(l-pixel.Color.Lightness) <= lightnessTolerance {
+							areaIndex = i
+							break
+						}
+					}
+				}
+
+				if areaIndex != -1 {
+					break
+				}
+			}
+
+			// Insert new area
+			if areaIndex == -1 {
+				areaIndex = len(hueAreas)
+				hueAreas = append(hueAreas, Area{})
+			}
+
+			hueAreas[areaIndex].Add(x, y, arn.HSLColor{
+				Hue:        h,
+				Saturation: s,
+				Lightness:  l,
+			})
+		}
+	}
+
+	fmt.Println(len(hueAreas), "areas")
+
+	// Build image from areas
+	for _, area := range hueAreas {
+		totalR := uint64(0)
+		totalG := uint64(0)
+		totalB := uint64(0)
+
+		// Calculate area average color
+		for _, pixel := range area.Pixels {
+			col := img.At(pixel.X, pixel.Y)
+			r, g, b, _ := col.RGBA()
+			totalR += uint64(r)
+			totalG += uint64(g)
+			totalB += uint64(b)
+		}
+
+		averageR := float64(totalR/uint64(len(area.Pixels))) / max
+		averageG := float64(totalG/uint64(len(area.Pixels))) / max
+		averageB := float64(totalB/uint64(len(area.Pixels))) / max
+
+		area.AverageColor = color.RGBA{
+			R: uint8(averageR * 255),
+			G: uint8(averageG * 255),
+			B: uint8(averageB * 255),
+			A: 255,
+		}
+
+		for _, pixel := range area.Pixels {
+			clone.Set(pixel.X, pixel.Y, area.AverageColor)
+		}
+	}
+
+	return clone
+}