Add favicon-gen tool to generate PNG and ICO favicons from SVG sources (#22)

cmd/favicon-gen/main.go

@@ -0,0 +1,152 @@
+// Package main provides a utility to generate PNG and ICO favicons from SVG source files.
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+	"log"
+	"os"
+	"path/filepath"
+
+	"github.com/srwiley/oksvg"
+	"github.com/srwiley/rasterx"
+)
+
+func main() {
+	mediaDir := "pkg/service/handlers/web/img"
+	files := []string{"favicon-braille", "favicon-morse"}
+
+	for _, name := range files {
+		svgPath := filepath.Join(mediaDir, name+".svg")
+		pngPath := filepath.Join(mediaDir, name+".png")
+		icoPath := filepath.Join(mediaDir, name+".ico")
+
+		fmt.Printf("Processing %s...\n", name)
+
+		// 1. Render SVG to PNG
+		img, err := renderSVG(svgPath, 32, 32)
+		if err != nil {
+			log.Fatalf("Failed to render %s: %v", svgPath, err)
+		}
+
+		f, err := os.Create(pngPath)
+		if err != nil {
+			log.Fatalf("Failed to create %s: %v", pngPath, err)
+		}
+
+		if err := png.Encode(f, img); err != nil {
+			f.Close()
+			log.Fatalf("Failed to encode PNG %s: %v", pngPath, err)
+		}
+
+		f.Close()
+		fmt.Printf("Created %s\n", pngPath)
+
+		// 2. Create ICO (containing multiple sizes)
+		sizes := []int{16, 32, 48}
+
+		var images []image.Image
+
+		for _, s := range sizes {
+			m, err := renderSVG(svgPath, s, s)
+			if err != nil {
+				log.Fatalf("Failed to render %s at size %d: %v", svgPath, s, err)
+			}
+
+			images = append(images, m)
+		}
+
+		if err := writeICO(icoPath, images); err != nil {
+			log.Fatalf("Failed to write ICO %s: %v", icoPath, err)
+		}
+
+		fmt.Printf("Created %s\n", icoPath)
+	}
+}
+
+func renderSVG(path string, w, h int) (image.Image, error) {
+	in, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer in.Close()
+
+	icon, err := oksvg.ReadIconStream(in)
+	if err != nil {
+		return nil, err
+	}
+
+	icon.SetTarget(0, 0, float64(w), float64(h))
+	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
+	gv := rasterx.NewScannerGV(w, h, rgba, rgba.Bounds())
+	dasher := rasterx.NewDasher(w, h, gv)
+	icon.Draw(dasher, 1.0)
+
+	return rgba, nil
+}
+
+// Simple ICO encoder that wraps PNGs
+func writeICO(path string, images []image.Image) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	bw := bufio.NewWriter(f)
+	defer bw.Flush()
+
+	// ICONDIR header
+	// Reserved (2), Type (2), Count (2)
+	binary.Write(bw, binary.LittleEndian, uint16(0))
+	binary.Write(bw, binary.LittleEndian, uint16(1)) // 1 = ICO
+	binary.Write(bw, binary.LittleEndian, uint16(len(images)))
+
+	var pngData [][]byte
+
+	for _, img := range images {
+		var buf bytes.Buffer
+		if err := png.Encode(&buf, img); err != nil {
+			return err
+		}
+
+		pngData = append(pngData, buf.Bytes())
+	}
+
+	offset := uint32(6 + len(images)*16)
+	for i, img := range images {
+		b := img.Bounds()
+
+		width := uint8(b.Dx())
+		if b.Dx() >= 256 {
+			width = 0
+		}
+
+		height := uint8(b.Dy())
+		if b.Dy() >= 256 {
+			height = 0
+		}
+
+		// ICONDIRENTRY
+		bw.WriteByte(width)
+		bw.WriteByte(height)
+		bw.WriteByte(0)                                   // Color count
+		bw.WriteByte(0)                                   // Reserved
+		binary.Write(bw, binary.LittleEndian, uint16(1))  // Planes (1)
+		binary.Write(bw, binary.LittleEndian, uint16(32)) // Bits per pixel (32)
+		binary.Write(bw, binary.LittleEndian, uint32(len(pngData[i])))
+		binary.Write(bw, binary.LittleEndian, offset)
+
+		offset += uint32(len(pngData[i]))
+	}
+
+	for _, data := range pngData {
+		bw.Write(data)
+	}
+
+	return nil
+}