feat: Add VLW font generation script and embedded font asset

FontGen/gen_vlw.py

@@ -0,0 +1,114 @@
+#!/usr/bin/env python3
+"""
+Generate a VLW font file compatible with LovyanGFX / M5GFX.
+
+VLW format (all big-endian int32), verified against lgfx_fonts.cpp:
+  Header (6 x int32):
+    [0] glyph_count
+    [1] vlw_encoder_version (write 8, matches Processing default)
+    [2] font_size (points)
+    [3] reserved / discard
+    [4] ascent
+    [5] descent
+
+  Per glyph (7 x int32), at offset 24:
+    [0] codepoint
+    [1] height
+    [2] width
+    [3] xAdvance
+    [4] dY  (y delta from baseline: ascent_px - bitmap_top)
+    [5] gdX (x delta from cursor:   bitmap_left / lsb)
+    [6] reserved (0)
+
+  Bitmaps (at offset 24 + gCount*28):
+    width * height bytes each, 1 byte per pixel (0=off, 255=on)
+"""
+
+import struct
+import math
+import freetype
+
+FONT_PATH = "/usr/share/fonts/Unifont/Unifont.ttf"
+SIZE_PT   = 24
+DPI       = 96
+GLYPHS    = "ʘ⌐■★()>_<Ox "
+OUT       = "unifont24.vlw"
+OUT_H     = "../src/unifont24_vlw.h"
+
+face = freetype.Face(FONT_PATH)
+face.set_char_size(SIZE_PT * 64, 0, DPI, 0)
+
+metrics_face = face.size
+ascent_px  = math.ceil(metrics_face.ascender  / 64)
+descent_px = math.ceil(-metrics_face.descender / 64)  # positive
+
+glyphs_data = []  # (codepoint, height, width, xAdvance, dY, gdX, pixels)
+
+for ch in GLYPHS:
+    cp = ord(ch)
+    # Grayscale render — gives 1 byte per pixel output
+    face.load_char(cp, freetype.FT_LOAD_RENDER)
+    slot   = face.glyph
+    bitmap = slot.bitmap
+
+    w      = bitmap.width
+    h      = bitmap.rows
+    gdX    = slot.bitmap_left              # x offset from cursor
+    dY     = slot.bitmap_top               # y delta from baseline (above baseline = positive)
+    xAdv   = math.ceil(slot.advance.x / 64)
+
+    # Grayscale pitch may be wider than width — trim to width bytes per row
+    # FreeType renders top-to-bottom in FT_PIXEL_MODE_GRAY — no reversal needed
+    pitch  = bitmap.pitch
+    raw    = bytes(bitmap.buffer)
+    pixels = bytearray()
+    for row in range(h):
+        pixels += raw[row * pitch: row * pitch + w]
+
+    glyphs_data.append((cp, h, w, xAdv, dY, gdX, bytes(pixels)))
+    print(f"  U+{cp:04X} '{ch}'  adv={xAdv}  {w}x{h}  gdX={gdX} dY={dY}")
+
+# MUST be sorted ascending by codepoint — getUnicodeIndex uses lower_bound
+glyphs_data.sort(key=lambda g: g[0])
+
+with open(OUT, "wb") as f:
+    # Header — 6 int32s
+    f.write(struct.pack(">iiiiii",
+        len(glyphs_data),  # [0] glyph count
+        8,                 # [1] vlw encoder version
+        SIZE_PT,           # [2] font size in points
+        0,                 # [3] reserved
+        ascent_px,         # [4] ascent
+        descent_px,        # [5] descent
+    ))
+    # Glyph records
+    for cp, h, w, xAdv, dY, gdX, _ in glyphs_data:
+        f.write(struct.pack(">iiiiiii", cp, h, w, xAdv, dY, gdX, 0))
+    # Bitmaps (1 byte per pixel)
+    for _, _, _, _, _, _, pixels in glyphs_data:
+        f.write(pixels)
+
+print(f"\nWrote '{OUT}'  ({len(glyphs_data)} glyphs, size={SIZE_PT}pt @ {DPI}dpi)")
+print(f"Ascent={ascent_px}  Descent={descent_px}")
+
+# C header for embedding in firmware flash
+vlw_bytes = open(OUT, "rb").read()
+with open(OUT_H, "w") as h_file:
+    h_file.write("#pragma once\n")
+    h_file.write("#include <stdint.h>\n\n")
+    h_file.write(f"// Auto-generated by gen_vlw.py — {len(glyphs_data)} glyphs, {SIZE_PT}pt\n")
+    h_file.write(f"// Usage: M5.Display.loadFont(unifont24_vlw);\n\n")
+    h_file.write(f"static const uint8_t unifont24_vlw[] = {{\n")
+    for i, b in enumerate(vlw_bytes):
+        if i % 16 == 0:
+            h_file.write("  ")
+        h_file.write(f"0x{b:02X},")
+        if i % 16 == 15:
+            h_file.write("\n")
+        else:
+            h_file.write(" ")
+    h_file.write("\n};\n")
+
+print(f"Wrote '{OUT_H}'  ({len(vlw_bytes)} bytes)")
+
+