agent-tools/bitmap-font-maker/main.go

// fontc turns .font text files (pixel glyph grids) into font atlases
// (PNG + JSON metrics) and renders text strings to images.
package main

import (
	"flag"
	"fmt"
	"image/color"
	"os"
	"path/filepath"
	"strings"

	"gitea.brasse-pc.eu/brasse/agent-tools/bitmap-font-maker/font"
)

var version = "dev"

const usage = `fontc - bitmap font maker for agents

Usage:
  fontc build <file.font> [flags]     build atlas PNG + metrics JSON
  fontc render <file.font> <text> [flags]
                                      render a text string to PNG
  fontc info <file.font>              validate + list glyphs
  fontc preview <file.font> <text>    draw text in the terminal
  fontc version

Build flags:
  -o <base>        output base name -> <base>.png + <base>.json
                   (default: font file name without extension)

Render flags:
  -o <path>        output PNG (default text.png)
  --scale <n>      integer upscale, default 1
  --color <c>      text color (#RRGGBB, CSS names not supported here), default #FFFFFF
  Use \n in <text> for line breaks.

The .font format:
  font: tiny5          optional name
  spacing: 1           px between glyphs (default 1)
  space-width: 3       advance of ' ' (default: width of '0')
  line-height: 7       default: glyph height + 1
  baseline: 5          default: glyph height

  glyph A:
    .#.
    #.#
    ###
    #.#
    #.#

'#' = pixel on, '.' = off. All glyphs share one height; widths may
differ (proportional). The atlas draws glyphs in white so engines can
tint them; metrics JSON carries x/y/w/h/advance per glyph.
`

func main() {
	if len(os.Args) < 2 {
		fmt.Print(usage)
		os.Exit(2)
	}
	switch os.Args[1] {
	case "build":
		cmdBuild(os.Args[2:])
	case "render":
		cmdRender(os.Args[2:])
	case "info":
		cmdInfo(os.Args[2:])
	case "preview":
		cmdPreview(os.Args[2:])
	case "version", "--version", "-v":
		fmt.Println("fontc", version)
	case "help", "--help", "-h":
		fmt.Print(usage)
	default:
		die("unknown command %q — run 'fontc help'", os.Args[1])
	}
}

// parseInterspersed lets flags appear before or after positional args.
func parseInterspersed(fs *flag.FlagSet, args []string) {
	var flags, pos []string
	for i := 0; i < len(args); i++ {
		a := args[i]
		if len(a) > 1 && a[0] == '-' {
			flags = append(flags, a)
			name := strings.TrimLeft(a, "-")
			if !strings.Contains(name, "=") {
				f := fs.Lookup(name)
				isBool := false
				if f != nil {
					if bv, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bv.IsBoolFlag() {
						isBool = true
					}
				}
				if !isBool && i+1 < len(args) {
					i++
					flags = append(flags, args[i])
				}
			}
		} else {
			pos = append(pos, a)
		}
	}
	fs.Parse(append(flags, pos...))
}

func cmdBuild(args []string) {
	fs := flag.NewFlagSet("build", flag.ExitOnError)
	out := fs.String("o", "", "output base name")
	parseInterspersed(fs, args)
	if fs.NArg() != 1 {
		die("build takes exactly one .font file")
	}
	ft, err := font.ParseFile(fs.Arg(0))
	if err != nil {
		die("%v", err)
	}
	base := *out
	if base == "" {
		base = strings.TrimSuffix(fs.Arg(0), filepath.Ext(fs.Arg(0)))
	}
	base = strings.TrimSuffix(base, ".png")
	img, metrics := ft.BuildAtlas(filepath.Base(base) + ".png")

	pngF, err := os.Create(base + ".png")
	if err != nil {
		die("%v", err)
	}
	defer pngF.Close()
	if err := font.WritePNG(pngF, img); err != nil {
		die("%v", err)
	}
	jsonF, err := os.Create(base + ".json")
	if err != nil {
		die("%v", err)
	}
	defer jsonF.Close()
	if err := font.WriteMetrics(jsonF, metrics); err != nil {
		die("%v", err)
	}
	b := img.Bounds()
	fmt.Printf("%s.png  (%dx%d atlas, %d glyphs)\n%s.json\n", base, b.Dx(), b.Dy(), len(ft.Order), base)
}

func parseHexColor(s string) (r, g, b uint8, err error) {
	s = strings.TrimPrefix(strings.TrimSpace(s), "#")
	if len(s) != 6 {
		return 0, 0, 0, fmt.Errorf("color must be #RRGGBB, got %q", s)
	}
	var v [3]uint8
	for i := 0; i < 3; i++ {
		var n int
		if _, err := fmt.Sscanf(s[i*2:i*2+2], "%02x", &n); err != nil {
			return 0, 0, 0, fmt.Errorf("bad hex color %q", s)
		}
		v[i] = uint8(n)
	}
	return v[0], v[1], v[2], nil
}

func cmdRender(args []string) {
	fs := flag.NewFlagSet("render", flag.ExitOnError)
	out := fs.String("o", "text.png", "output PNG")
	scale := fs.Int("scale", 1, "integer upscale")
	col := fs.String("color", "#FFFFFF", "text color #RRGGBB")
	parseInterspersed(fs, args)
	if fs.NArg() != 2 {
		die("render takes a .font file and a text string")
	}
	ft, err := font.ParseFile(fs.Arg(0))
	if err != nil {
		die("%v", err)
	}
	r, g, b, err := parseHexColor(*col)
	if err != nil {
		die("%v", err)
	}
	img, warnings := ft.RenderText(fs.Arg(1), *scale, rgba(r, g, b))
	for _, w := range warnings {
		fmt.Fprintln(os.Stderr, "fontc:", w)
	}
	f, err := os.Create(*out)
	if err != nil {
		die("%v", err)
	}
	defer f.Close()
	if err := font.WritePNG(f, img); err != nil {
		die("%v", err)
	}
	bd := img.Bounds()
	fmt.Printf("%s  (%dx%d px)\n", *out, bd.Dx(), bd.Dy())
}

func cmdInfo(args []string) {
	if len(args) != 1 {
		die("info takes exactly one .font file")
	}
	ft, err := font.ParseFile(args[0])
	if err != nil {
		die("%v", err)
	}
	fmt.Printf("font:        %s\n", ft.Name)
	fmt.Printf("height:      %d px\n", ft.Height)
	fmt.Printf("line-height: %d px\n", ft.LineHeight)
	fmt.Printf("baseline:    %d\n", ft.Baseline)
	fmt.Printf("spacing:     %d px\n", ft.Spacing)
	fmt.Printf("space-width: %d px\n", ft.SpaceWidth)
	fmt.Printf("glyphs:      %d\n", len(ft.Order))
	var chars []string
	for _, r := range ft.SortedChars() {
		chars = append(chars, string(r))
	}
	fmt.Printf("  %s\n", strings.Join(chars, " "))
	fmt.Println("valid:       yes")
}

func cmdPreview(args []string) {
	if len(args) != 2 {
		die("preview takes a .font file and a text string")
	}
	ft, err := font.ParseFile(args[0])
	if err != nil {
		die("%v", err)
	}
	img, warnings := ft.RenderText(args[1], 1, rgba(255, 255, 255))
	for _, w := range warnings {
		fmt.Fprintln(os.Stderr, "fontc:", w)
	}
	b := img.Bounds()
	for y := 0; y < b.Dy(); y += 2 {
		var sb strings.Builder
		for x := 0; x < b.Dx(); x++ {
			top := img.NRGBAAt(x, y).A >= 128
			bot := y+1 < b.Dy() && img.NRGBAAt(x, y+1).A >= 128
			switch {
			case top && bot:
				sb.WriteRune('█')
			case top:
				sb.WriteRune('▀')
			case bot:
				sb.WriteRune('▄')
			default:
				sb.WriteByte(' ')
			}
		}
		fmt.Println(sb.String())
	}
}

func rgba(r, g, b uint8) color.NRGBA {
	return color.NRGBA{R: r, G: g, B: b, A: 255}
}

func die(format string, a ...any) {
	fmt.Fprintf(os.Stderr, "fontc: "+format+"\n", a...)
	os.Exit(1)
}