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image.go
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image.go
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package main
/**************
* Image code *
**************/
import (
"fmt"
"image"
"image/color"
_ "image/gif"
_ "image/jpeg"
"log"
"math/rand"
"runtime"
)
type mutation struct {
x, y, w, h int
rgb color.RGBA
}
func abs(x, y uint8) int {
if x > y {
return int(x - y)
} else {
return int(y - x)
}
}
func myRGBAAt(p *image.RGBA, x, y int) color.RGBA {
i := p.PixOffset(x, y)
return color.RGBA{p.Pix[i+0], p.Pix[i+1], p.Pix[i+2], p.Pix[i+3]}
}
// Returns an image which approximately recreates the input image.
func approximate(
target *image.RGBA,
TRIES,
MUTATIONS,
PIXELSAMPLING int,
eventBroadcast chan *Event,
) (*image.RGBA, int) {
NCPU := runtime.NumCPU()
fmt.Printf("%v\n", NCPU)
// Start with a white background.
approx := image.NewRGBA(target.Bounds())
imgW := approx.Bounds().Dx()
imgH := approx.Bounds().Dy()
start := mutation{0, 0, imgW, imgH, color.RGBA{255, 255, 255, 255}}
colors := colorsIn(target)
mutate(approx, start)
score, err := imgDist(target, approx)
if err != nil {
log.Fatal(err)
}
cm := make(chan mutation, NCPU)
cs := make(chan int, NCPU)
for i := 0; i < TRIES; i++ {
// Spawn NCPU goroutines, each of which does MUTATIONS/NCPU mutations.
for ch := 0; ch < NCPU; ch++ {
// Calculate the best mutation on this goroutine.
go findMutation(score, NCPU, MUTATIONS, approx, target, colors, cm, cs)
}
// Find the best mutation amongst all the goroutines.
bestMutation := <-cm
bestScore := <-cs
for ch := 1; ch < NCPU; ch++ {
m := <-cm
score = <-cs
if score < bestScore {
bestMutation = m
bestScore = score
}
}
// Apply the best mutation,
// then restart the loop to place a new rectangle in the image.
mutate(approx, bestMutation)
eventBroadcast <- &Event{Name: "mutation", Properties: map[string]string{
"progress": fmt.Sprint(i),
"total": fmt.Sprint(TRIES),
}}
}
return approx, score
}
func findMutation(
score,
NCPU,
MUTATIONS int,
approx,
target *image.RGBA,
colors []color.RGBA,
cm chan mutation,
cs chan int,
) {
imgW := approx.Bounds().Dx()
imgH := approx.Bounds().Dy()
cachedScore := score
bestScore := cachedScore
var bestMutation mutation
// Try MUTATIONS different mutations and keep the best one.
for try := 0; try < MUTATIONS/NCPU; try++ {
// Generate a mutation
w := rand.Intn(imgW)
h := rand.Intn(imgH)
x := rand.Intn(imgW - w)
y := rand.Intn(imgH - h)
rgb := colors[rand.Intn(len(colors))]
m := mutation{x, y, w, h, rgb}
// Save this mutation if it's the best.
tryScore := imgDistMutated(approx, target, cachedScore, m, PIXELSAMPLING)
if tryScore < bestScore {
bestScore = tryScore
bestMutation = m
}
}
cm <- bestMutation
cs <- bestScore
}
// Returns a slice containing all colors used in the image, and
// a map from each point/pixel in the image to its color.
// looking up colors in this map is 100x faster than using img.at again.
func colorsIn(img *image.RGBA) []color.RGBA {
colsList := make([]color.RGBA, 1000)
cols := make(map[color.RGBA]bool)
for x := img.Bounds().Min.X; x < img.Bounds().Max.X; x++ {
for y := img.Bounds().Min.Y; y < img.Bounds().Max.Y; y++ {
color := myRGBAAt(img, x, y)
if _, prs := cols[color]; !prs {
cols[color] = true
colsList = append(colsList, color)
}
}
}
return colsList
}
// RGB distance between two colors.
func colorDist(c1, c2 color.RGBA) int {
sum := abs(c1.R, c2.R)
sum += abs(c1.G, c2.G)
sum += abs(c1.B, c2.B)
return int(sum)
}
// Colors a subrect (x,y,w,h) in the canvas to color (r,g,b).
func mutate(img *image.RGBA, m mutation) error {
// Check the mutated region fits inside the canvas.
if m.x+m.w > img.Bounds().Dx() || m.y+m.h > img.Bounds().Dy() {
return fmt.Errorf("Invalid mutation size.")
}
// Fill in the coloured region.
for i := m.x; i < m.w+m.x; i++ {
for j := m.y; j < m.h+m.y; j++ {
img.SetRGBA(i, j, m.rgb)
}
}
return nil
}
// Returns the pixelwise distance between two canvases.
func imgDist(img1, img2 *image.RGBA) (int, error) {
// Check the two canvases are the same size
if img1.Bounds() != img2.Bounds() {
return 0, fmt.Errorf("Can't compare different-sized images.")
}
sum := 0
for i := img1.Bounds().Min.X; i < img1.Bounds().Max.X; i++ {
for j := img1.Bounds().Min.Y; j < img1.Bounds().Max.Y; j++ {
sum += colorDist(myRGBAAt(img1, i, j), myRGBAAt(img2, i, j))
}
}
return sum, nil
}
// Returns the pixelwise distance between this canvas with a mutation and a second canvas of the same size.
func imgDistMutated(img, target *image.RGBA, cachedScore int, m mutation, PIXELSAMPLING int) int {
score := cachedScore
for i := m.x; i < m.x+m.w; i += PIXELSAMPLING {
for j := m.y; j < m.y+m.h; j += PIXELSAMPLING {
// Subtract the original color's score, add the mutated color's score.
col := myRGBAAt(target, i, j)
score -= colorDist(col, myRGBAAt(img, i, j))
score += colorDist(col, m.rgb)
}
}
return score
}
func toRGBA(_target image.Image) *image.RGBA {
target := image.NewRGBA(_target.Bounds())
for x := target.Bounds().Min.X; x < target.Bounds().Max.X; x++ {
for y := target.Bounds().Min.Y; y < target.Bounds().Max.Y; y++ {
target.Set(x, y, _target.At(x, y))
}
}
return target
}