subsys: fb: add support for generating CFB font headers at build time

Add script and cmake functions for automatically generating Character
Frame Buffer (CFB) font header files from image files, TrueType, or
OpenType font files.

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>

scripts/gen_cfb_font_header.py

@@ -0,0 +1,168 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2018 Henrik Brix Andersen <henrik@brixandersen.dk>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import sys
+
+from PIL import ImageFont
+from PIL import Image
+from PIL import ImageDraw
+
+PRINTABLE_MIN = 32
+PRINTABLE_MAX = 127
+
+def generate_element(image, charcode):
+    """Generate CFB font element for a given character code from an image"""
+    blackwhite = image.convert("1", dither=Image.NONE)
+    pixels = blackwhite.load()
+
+    if args.dump:
+        blackwhite.save("{}_{}.png".format(args.name, charcode))
+
+    if PRINTABLE_MIN <= charcode <= PRINTABLE_MAX:
+        char = " ({:c})".format(charcode)
+    else:
+        char = ""
+
+    args.output.write("""\t/* {:d}{} */\n\t{{\n""".format(charcode, char))
+
+    for col in range(0, args.width):
+        args.output.write("\t\t")
+        for octet in range(0, int(args.height / 8)):
+            value = ""
+            for bit in range(0, 8):
+                row = octet * 8 + bit
+                if pixels[col, row]:
+                    value = "0" + value
+                else:
+                    value = "1" + value
+            args.output.write("0x{:02x},".format(int(value, 2)))
+        args.output.write("\n")
+    args.output.write("\t},\n")
+
+def extract_font_glyphs():
+    """Extract font glyphs from a TrueType/OpenType font file"""
+    font = ImageFont.truetype(args.input, args.size)
+    for i in range(args.first, args.last + 1):
+        image = Image.new("RGB", (args.width, args.height), (255, 255, 255))
+        draw = ImageDraw.Draw(image)
+        draw.text((0, 0), chr(i), (0, 0, 0), font=font)
+        generate_element(image, i)
+
+def extract_image_glyphs():
+    """Extract font glyphs from an image file"""
+    image = Image.open(args.input)
+
+    x_offset = 0
+    for i in range(args.first, args.last + 1):
+        glyph = image.crop((x_offset, 0, x_offset + args.width, args.height))
+        generate_element(glyph, i)
+        x_offset += args.width
+
+def generate_header():
+    """Generate CFB font header file"""
+    guard = "__CFB_FONT_{:s}_{:d}{:d}_H__".format(args.name.upper(), args.width,
+                                                  args.height)
+
+    args.output.write("""/*
+ * This file was automatically generated using the following command:
+ * {cmd}
+ *
+ */
+
+#ifndef {guard}
+#define {guard}
+
+#include <zephyr.h>
+#include <display/cfb.h>
+
+const u8_t cfb_font_{name:s}_{width:d}{height:d}[{elem:d}][{b:.0f}] = {{\n"""
+                      .format(cmd=" ".join(sys.argv),
+                              guard=guard,
+                              name=args.name,
+                              width=args.width,
+                              height=args.height,
+                              elem=args.last - args.first + 1,
+                              b=args.width / 8 * args.height))
+
+    if args.type == "font":
+        extract_font_glyphs()
+    elif args.type == "image":
+        extract_image_glyphs()
+    elif args.input.name.lower().endswith((".otf", ".otc", ".ttf", ".ttc")):
+        extract_font_glyphs()
+    else:
+        extract_image_glyphs()
+
+    args.output.write("""
+}};
+
+FONT_ENTRY_DEFINE({name}_{width}{height},
+		  {width},
+		  {height},
+		  CFB_FONT_MONO_VPACKED,
+		  cfb_font_{name}_{width}{height},
+		  {first},
+		  {last}
+);
+
+#endif /* {guard} */""" .format(name=args.name, width=args.width,
+                                height=args.height, first=args.first,
+                                last=args.last, guard=guard))
+
+def parse_args():
+    """Parse arguments"""
+    global args
+    parser = argparse.ArgumentParser(
+        description="Character Frame Buffer (CFB) font header file generator",
+        formatter_class=argparse.RawDescriptionHelpFormatter)
+
+    parser.add_argument(
+        "-d", "--dump", action="store_true",
+        help="dump generated CFB font elements as images for preview")
+
+    group = parser.add_argument_group("input arguments")
+    group.add_argument(
+        "-i", "--input", required=True, type=argparse.FileType('rb'), metavar="FILE",
+        help="TrueType/OpenType file or image input file")
+    group.add_argument(
+        "-t", "--type", default="auto", choices=["auto", "font", "image"],
+        help="Input file type (default: %(default)s)")
+
+    group = parser.add_argument_group("font arguments")
+    group.add_argument(
+        "-s", "--size", type=int, default=10, metavar="POINTS",
+        help="TrueType/OpenType font size in points (default: %(default)s)")
+
+    group = parser.add_argument_group("output arguments")
+    group.add_argument(
+        "-o", "--output", type=argparse.FileType('w'), default="-", metavar="FILE",
+        help="CFB font header file (default: stdout)")
+    group.add_argument(
+        "-x", "--width", required=True, type=int,
+        help="width of the CFB font elements in pixels")
+    group.add_argument(
+        "-y", "--height", required=True, type=int, choices=range(8, 128, 8),
+        help="height of the CFB font elements in pixels")
+    group.add_argument(
+        "-n", "--name", default="custom",
+        help="name of the CFB font entry (default: %(default)s)")
+    group.add_argument(
+        "--first", type=int, default=PRINTABLE_MIN, metavar="CHARCODE",
+        help="character code mapped to the first CFB font element (default: %(default)s)")
+    group.add_argument(
+        "--last", type=int, default=PRINTABLE_MAX, metavar="CHARCODE",
+        help="character code mapped to the last CFB font element (default: %(default)s)")
+
+    args = parser.parse_args()
+
+def main():
+    """Parse arguments and generate CFB font header file"""
+    parse_args()
+    generate_header()
+
+if __name__ == "__main__":
+    main()