cmd/fontpreview: add tool with generated font previews

Add a font preview generator that renders sample PNGs for each bundled font.

Signed-off-by: deadprogram <ron@hybridgroup.com>

Author: deadprogram

cmd/fontpreview/main.go

@@ -0,0 +1,189 @@
+// fontpreview renders a sample of each tinyfont font to a PNG in the images/ directory.
+// Run from the repo root: go run ./cmd/fontpreview
+package main
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+	"os"
+	"path/filepath"
+
+	"tinygo.org/x/tinyfont"
+	"tinygo.org/x/tinyfont/freemono"
+	"tinygo.org/x/tinyfont/freesans"
+	"tinygo.org/x/tinyfont/freeserif"
+	"tinygo.org/x/tinyfont/gophers"
+	"tinygo.org/x/tinyfont/notoemoji"
+	"tinygo.org/x/tinyfont/notosans"
+	"tinygo.org/x/tinyfont/proggy"
+	"tinygo.org/x/tinyfont/shnm"
+)
+
+// imgDisplay is an in-memory display backed by an image.RGBA.
+type imgDisplay struct {
+	img *image.RGBA
+}
+
+func (d *imgDisplay) SetPixel(x, y int16, c color.RGBA) {
+	b := d.img.Bounds()
+	if int(x) >= 0 && int(x) < b.Max.X && int(y) >= 0 && int(y) < b.Max.Y {
+		d.img.SetRGBA(int(x), int(y), c)
+	}
+}
+
+func (d *imgDisplay) Size() (int16, int16) {
+	b := d.img.Bounds()
+	return int16(b.Max.X), int16(b.Max.Y)
+}
+
+func (d *imgDisplay) Display() error { return nil }
+
+// measureWidth returns the pixel width of text rendered in font.
+func measureWidth(font tinyfont.Fonter, text string) int {
+	w := 0
+	for _, r := range text {
+		g := font.GetGlyph(r)
+		w += int(g.Info().XAdvance)
+	}
+	return w
+}
+
+// scaleImage returns a nearest-neighbour upscaled copy of src.
+func scaleImage(src *image.RGBA, scale int) *image.RGBA {
+	b := src.Bounds()
+	dst := image.NewRGBA(image.Rect(0, 0, b.Max.X*scale, b.Max.Y*scale))
+	for y := 0; y < b.Max.Y; y++ {
+		for x := 0; x < b.Max.X; x++ {
+			c := src.RGBAAt(x, y)
+			for dy := 0; dy < scale; dy++ {
+				for dx := 0; dx < scale; dx++ {
+					dst.SetRGBA(x*scale+dx, y*scale+dy, c)
+				}
+			}
+		}
+	}
+	return dst
+}
+
+// renderFontRows renders multiple rows of text in font and saves a PNG to outDir/name.png.
+// Small fonts are scaled up so they remain visible at a reasonable size.
+func renderFontRows(name string, font tinyfont.Fonter, rows []string, outDir string, extraBottomPadding int) error {
+	const padding = 4
+	const fgVal = 0x00
+	const bg = 0xFF
+
+	yAdv := int(font.GetYAdvance())
+	if yAdv == 0 {
+		yAdv = 16
+	}
+
+	// Calculate max width and total height.
+	maxW := 0
+	for _, row := range rows {
+		w := measureWidth(font, row)
+		if w > maxW {
+			maxW = w
+		}
+	}
+
+	w := maxW + padding*2
+	h := len(rows)*yAdv + padding*2 + extraBottomPadding
+
+	img := image.NewRGBA(image.Rect(0, 0, w, h))
+	// White background.
+	white := color.RGBA{bg, bg, bg, 0xFF}
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			img.SetRGBA(x, y, white)
+		}
+	}
+
+	d := &imgDisplay{img}
+	fgColor := color.RGBA{fgVal, fgVal, fgVal, 0xFF}
+	for i, row := range rows {
+		y := int16(padding + i*yAdv + yAdv)
+		tinyfont.WriteLine(d, font, int16(padding), y, row, fgColor)
+	}
+
+	// Scale up small fonts so the image is at least ~48px tall.
+	scale := 1
+	switch {
+	case h <= 16:
+		scale = 5
+	case h <= 24:
+		scale = 4
+	case h <= 48:
+		scale = 2
+	}
+	if scale > 1 {
+		img = scaleImage(img, scale)
+	}
+
+	path := filepath.Join(outDir, name+".png")
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return png.Encode(f, img)
+}
+
+func main() {
+	const outDir = "images"
+
+	asciiRows := []string{
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+		"abcdefghijklmnopqrstuvwxyz",
+		"0123456789",
+		"!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~",
+	}
+
+	// Gophers font only shows uppercase.
+	gophersRows := []string{
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+	}
+
+	// A selection of emoji known to exist in the 12pt NotoEmoji font.
+	emojiRows := []string{
+		"☀♠♥♦⭐❤✅✨🎉🎊🔥💡",
+	}
+
+	// Japanese hiragana characters for shnm font.
+	japaneseRows := []string{
+		"あいうえおかきくけこ",
+		"さしすせそたちつてと",
+		"なにぬねのはひふへほ",
+	}
+
+	type fontEntry struct {
+		name               string
+		font               tinyfont.Fonter
+		rows               []string
+		extraBottomPadding int
+	}
+
+	fonts := []fontEntry{
+		{"freemono", &freemono.Regular12pt7b, asciiRows, 8},
+		{"freesans", &freesans.Regular12pt7b, asciiRows, 8},
+		{"freeserif", &freeserif.Regular12pt7b, asciiRows, 8},
+		{"gophers", &gophers.Regular32pt, gophersRows, 0},
+		{"notoemoji", &notoemoji.NotoEmojiRegular12pt, emojiRows, 0},
+		{"notosans", &notosans.Notosans12pt, asciiRows, 0},
+		{"proggy", &proggy.TinySZ8pt7b, asciiRows, 0},
+		{"shnm", &shnm.Shnmk12, japaneseRows, 0},
+		{"org_01", &tinyfont.Org01, asciiRows, 4},
+		{"picopixel", &tinyfont.Picopixel, asciiRows, 4},
+		{"tiny3x3a2pt7b", &tinyfont.Tiny3x3a2pt7b, asciiRows, 0},
+		{"tomthumb", &tinyfont.TomThumb, asciiRows, 4},
+	}
+
+	for _, fe := range fonts {
+		if err := renderFontRows(fe.name, fe.font, fe.rows, outDir, fe.extraBottomPadding); err != nil {
+			fmt.Fprintf(os.Stderr, "error rendering %s: %v\n", fe.name, err)
+		} else {
+			fmt.Printf("rendered %s → %s/%s.png\n", fe.name, outDir, fe.name)
+		}
+	}
+}