mtsatellite/common/colors.go

// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package common

import (
	"bufio"
	"fmt"
	"image/color"
	"os"
	"sort"
	"strings"
)

type Colors struct {
	Colors      []color.RGBA
	NameIndex   map[string]int32
	Transparent int
}

type namedColor struct {
	name  string
	color color.RGBA
}

type sortByAlpha []namedColor

func (colors sortByAlpha) Less(i, j int) bool {
	return colors[i].color.A < colors[j].color.A
}

func (colors sortByAlpha) Len() int {
	return len(colors)
}

func (colors sortByAlpha) Swap(i, j int) {
	colors[i], colors[j] = colors[j], colors[i]
}

func ParseColors(filename string) (colors *Colors, err error) {

	var file *os.File
	if file, err = os.Open(filename); err != nil {
		return
	}
	defer file.Close()

	cols := make([]namedColor, 0, 2200)

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(line, "#") {
			continue
		}
		c := color.RGBA{A: 0xff}
		var name string
		if n, _ := fmt.Sscanf(
			line, "%s %d %d %d %d", &name, &c.R, &c.G, &c.B, &c.A); n > 0 {
			cols = append(cols, namedColor{name: name, color: c})
		}
	}
	err = scanner.Err()

	// Sort transparent colors to front. Makes it easier to figure out
	// if an index corresponds to a transparent color (i < Transparent).
	sort.Sort(sortByAlpha(cols))

	cs := make([]color.RGBA, len(cols))
	nameIndex := make(map[string]int32, len(cols))

	transparent := 0
	for i, nc := range cols {
		if nc.color.A < 0xff {
			transparent++
		}
		cs[i] = nc.color
		nameIndex[nc.name] = int32(i)
	}
	colors = &Colors{Colors: cs, NameIndex: nameIndex, Transparent: transparent}
	return
}