Go script to read a png image like those found at http://scrollboss.illmosis.net/sprites.php?g=xmen-konamiarc to figure out how to make one with Perler beads (WIP)

perler.go

package main

import (
	"flag"
	"fmt"
	"image"
	"image/color"
	"image/png"
	"log"
	"os"
	"strconv"
)

const (
	pegboardH     = 29
	pegboardW     = 29
	perlerWidthMm = 4.60  // Millimeters width of a perler bead
	rgb8to16      = 0x101 // Multiply an 8-bit RGB value to 16-bit
	newFilePrefix = "perlerized-"
)

var filename = flag.String("f", "", "Name of png file to perlerize")

func main() {
	flag.Parse()

	file, err := os.Open(*filename)
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	img, err := png.Decode(file)
	if err != nil {
		log.Fatal(err)
	}

	bounds := img.Bounds()
	size := bounds.Size()
	w := size.X
	h := size.Y
	fmt.Printf("Image dimensions: %v x %v pixels\n", h, w)

	realH := strconv.FormatFloat(float64(h) * perlerWidthMm / 1000, 'g', 3, 64)
	realW := strconv.FormatFloat(float64(w) * perlerWidthMm / 1000, 'g', 3, 64)
	fmt.Printf("Physical dimensions: %s x %s meters ", realH, realW)

	boards := w / pegboardW * h / pegboardH
	fmt.Printf("(%d pegboards)\n", boards)

	// Make a palette out of all the possible bead colors
	var palette color.Palette
	for k, _ := range paletteMap {
		palette = append(palette, k)
	}

	var total uint32
	colors := make(map[string]uint32)
	for i := bounds.Min.X; i < bounds.Max.X; i++ {
		for j := bounds.Min.Y; j < bounds.Max.Y; j++ {
			c := img.At(i, j)
			_, _, _, a := c.RGBA()
			if a == 0 {
				continue
			}

			conv := palette.Convert(c)
			v := paletteMap[conv]
			colors[v]++
			total++

		}
	}
	fmt.Printf("%d total beads\n=======\n", total)
	for k, v := range colors {
		fmt.Printf("%s x %d\n", k, v)
	}

	paletted := palettedImage{img, palette}
	newFilename := newFilePrefix + *filename
	newFile, err := os.Create(newFilename)
	if err != nil {
		log.Fatal(err)
	}
	defer newFile.Close()
	png.Encode(newFile, paletted)
	fmt.Println("Created:", newFilename)
}

type myColor struct {
	r, g, b uint32
}

func (m myColor) RGBA() (r, g, b, a uint32) {
	return m.r * rgb8to16,
		m.g * rgb8to16,
		m.b * rgb8to16,
		255 * rgb8to16
}
func col(r, g, b uint32) color.Color {
	return myColor{r, g, b}
}

type palettedImage struct {
	orig    image.Image
	palette color.Palette
}

func (p palettedImage) ColorIndexAt(x, y int) uint8 {
	return uint8(p.palette.Index(p.orig.At(x, y)))
}
func (p palettedImage) At(x, y int) color.Color {
	_, _, _, a := p.orig.At(x, y).RGBA()
	if a == 0 {
		return color.Transparent
	}
	return p.palette.Convert(p.orig.At(x, y))
}
func (p palettedImage) Bounds() image.Rectangle {
	return p.orig.Bounds()
}
func (p palettedImage) ColorModel() color.Model {
	return color.ModelFunc(func (in color.Color) color.Color {
		return p.palette.Convert(in)
	})
}

// Map of available Perler bead colors to their name
// From https://sites.google.com/site/degenatrons/other-stuff/bead-pattern-generator
var paletteMap = map[color.Color]string{
	col(0, 0, 0):       "P18-BLACK",
	col(95, 100, 100):  "P92-DARK-GREY",
	col(145, 150, 155): "H17-GREY",
	col(150, 155, 160): "P17-GREY",
	col(160, 160, 155): "N08-ASH-GREY",
	col(255, 255, 255): "P01-WHITE",
	col(255, 210, 75):  "N14-YELLOW",
	col(255, 215, 90):  "H03-YELLOW",
	col(255, 235, 55):  "P03-YELLOW",
	col(245, 240, 125): "H43-PASTEL-YELLOW",
	col(245, 240, 155): "P56-PASTEL-YELLOW",
	col(255, 245, 175): "N21-LIGHT-YELLOW",
	col(250, 240, 195): "H02-CREAM",
	col(240, 230, 195): "P02-CREAM",
	col(245, 225, 215): "N12-IVORY",
	col(230, 225, 225): "N10-LIGHT-GREY",
	col(250, 200, 85):  "P57-CHEDDAR",
	col(240, 175, 95):  "H60-TEDDY-BEAR",
	col(240, 150, 110): "P90-BUTTERSCOTCH",
	col(225, 185, 150): "H27-BEIGE",
	col(240, 195, 150): "N07-SKIN",
	col(185, 160, 145): "N06-BEIGE",
	col(205, 165, 135): "P35-TAN",
	col(210, 155, 125): "N20-LIGHT-BROWN",
	col(190, 125, 85):  "N05-BUTTERSCOTCH",
	col(190, 130, 100): "H21-LIGHT-BROWN",
	col(150, 85, 100):  "N04-WINE-RED",
	col(115, 75, 85):   "H30-BURGUNDY",
	col(90, 85, 80):    "N02-DARK-BROWN",
	col(105, 75, 80):   "N03-BROWN-MEDIUM",
	col(110, 90, 85):   "P12-BROWN",
	col(100, 75, 80):   "H12-BROWN",
	col(165, 90, 90):   "P20-RUST",
	col(170, 85, 80):   "H20-BROWN",
	col(145, 105, 100): "N27-BROWN",
	col(160, 130, 95):  "P21-LIGHT-BROWN",
	col(195, 80, 115):  "H29-RASPBERRY",
	col(190, 70, 115):  "P88-RASPBERRY",
	col(175, 75, 85):   "H22-DARK-RED",
	col(215, 65, 85):   "N19-LIGHT-RED",
	col(205, 70, 90):   "P05-RED",
	col(240, 105, 95):  "H04-ORANGE",
	col(255, 115, 80):  "P04-ORANGE",
	col(225, 160, 85):  "N29-PEARL-ORANGE",
	col(255, 120, 165): "N25-OLD-ROSE",
	col(255, 95, 200):  "H32-FUCHSIA",
	col(255, 60, 130):  "P38-MAGENTA",
	col(255, 90, 115):  "P59-HOT-CORAL",
	col(255, 120, 140): "H44-PASTEL-CORAL",
	col(255, 150, 160): "P63-BLUSH",
	col(245, 200, 190): "N18-LIGHT-PINK",
	col(250, 205, 195): "P33-PEACH",
	col(240, 170, 165): "H26-FLESH",
	col(255, 185, 150): "N26-LIGHT-ORANGE",
	col(240, 130, 175): "P06-BUBBLE-GUM",
	col(240, 95, 165):  "P83-PINK",
	col(230, 135, 200): "H48-PASTEL-PINK",
	col(215, 155, 200): "P55-PASTEL-PINK",
	col(245, 155, 175): "H06-PINK",
	col(245, 200, 230): "P79-LIGHT-PINK",
	col(155, 135, 205): "P54-PASTEL-LAVENDER",
	col(165, 140, 205): "H45-PASTEL-PURPLE",
	col(200, 185, 240): "N24-LILAC",
	col(115, 90, 155):  "N11-PURPLE",
	col(5, 150, 205):   "P62-TURQUOISE",
	col(85, 125, 185):  "P70-PERIWINKLE",
	col(45, 130, 200):  "P09-LIGHT-BLUE",
	col(0, 120, 210):   "N17-BLUE",
	col(25, 105, 180):  "H09-LIGHT-BLUE",
	col(35, 85, 160):   "H08-BLUE",
	col(35, 80, 145):   "P08-DARK-BLUE",
	col(175, 90, 160):  "P60-PLUM",
	col(120, 95, 155):  "P07-PURPLE",
	col(120, 90, 145):  "H07-PURPLE",
	col(105, 160, 175): "H31-TURQUOISE",
	col(90, 160, 205):  "P52-PASTEL-BLUE",
	col(80, 170, 225):  "H46-PASTEL-BLUE",
	col(90, 170, 235):  "N23-PASTEL-BLUE",
	col(160, 205, 245): "N28-LIGHT-BLUE",
	col(160, 215, 225): "P58-TOOTHPASTE",
	col(200, 200, 120): "N30-OLIVE",
	col(135, 210, 145): "P53-PASTEL-GREEN",
	col(150, 230, 160): "H47-PASTEL-GREEN",
	col(125, 210, 80):  "P61-KIWI-LIME",
	col(70, 85, 90):    "H28-DARK-GREEN",
	col(70, 100, 90):   "N09-DARK-GREEN",
	col(40, 140, 100):  "P10-DARK-GREEN",
	col(35, 125, 95):   "H10-GREEN",
	col(50, 145, 100):  "N16-GREEN",
	col(0, 150, 165):   "P91-PARROT-GREEN",
	col(70, 195, 165):  "H11-LIGHT-GREEN",
	col(75, 195, 180):  "P11-LIGHT-GREEN",
	col(115, 185, 115): "P80-BRIGHT-GREEN",
	col(55, 170, 100):  "N22-PEARL-GREEN",
}

Where did you find the rgb values of the colors?