tools for generating glyph bitmaps for src/chars.rs

utils/README.md

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+This tool converts an image containing Unicode glyphs into Rust-compatible bitmap arrays for use in the `img2irc` project.
+
+## Workflow Overview
+
+1. **Create input files:**
+
+   * An **image file** with glyphs rendered horizontally, without gaps. Essentially a cropped screenshot of the rendered characters with no spaces in between.
+   * A **text file** listing the same glyphs separated by spaces.
+
+2. **Generate JSON bitmap data (`mkbitmap.py`).**
+
+3. **Convert JSON to Rust source (`mkrust.py`).**
+
+4. Replace `src/chars.rs` in `img2irc` with the generated Rust file and recompile.
+
+---
+
+## `mkbitmap.py`
+
+Slices an image into bitmaps and outputs JSON.
+
+**Arguments:**
+
+| Argument      | Description                                      |
+| ------------- | ------------------------------------------------ |
+| `chars_file`  | Text file containing glyphs separated by spaces. |
+| `image_file`  | Horizontal image of glyphs (no gaps).            |
+| `--icw`       | Input character width (pixels).                  |
+| `--ich`       | Input character height (pixels).                 |
+| `--threshold` | Black/white pixel threshold (0–255).             |
+| `--obw`       | Output bitmap width.                             |
+| `--obh`       | Output bitmap height.                            |
+| `--output`    | Output JSON filename.                            |
+
+**Example:**
+
+```bash
+./mkbitmap.py chars.txt chars.png --icw 20 --ich 40 --threshold 128 --obw 10 --obh 20 --output chars.json
+```
+
+---
+
+## `mkrust.py`
+
+Converts JSON bitmap data to Rust source code.
+
+**Arguments:**
+
+| Argument     | Description                   |
+| ------------ | ----------------------------- |
+| `input_json` | JSON file from `mkbitmap.py`. |
+| `output_rs`  | Output Rust source file.      |
+
+**Example:**
+
+```bash
+./mkrust.py chars.json chars.rs
+```
+
+Replace the resulting `chars.rs` in your `img2irc` project and recompile.
+
+You can use the included `chars.txt` and `chars.png` as an example.

utils/chars.txt

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utils/mkbitmap.py

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+#!/usr/bin/env python3
+import argparse
+import json
+from PIL import Image
+
+def main():
+    p = argparse.ArgumentParser(
+        description="Slice a row-image of glyphs into bitmaps and output JSON mapping."
+    )
+    p.add_argument('chars_file', help='Space-delimited glyphs text file (UTF-8)')
+    p.add_argument('image_file', help='Image with glyphs in one row, no gaps')
+    p.add_argument('--icw', type=int, required=True, help='Input char width (px)')
+    p.add_argument('--ich', type=int, required=True, help='Input char height (px)')
+    p.add_argument('--threshold', type=int, required=True, help='B/W threshold (0–255)')
+    p.add_argument('--obw', type=int, required=True, help='Output bitmap width')
+    p.add_argument('--obh', type=int, required=True, help='Output bitmap height')
+    p.add_argument('--output', required=True, help='Output JSON filename')
+    args = p.parse_args()
+
+    # 1) Read glyphs
+    with open(args.chars_file, 'r', encoding='utf-8') as f:
+        glyphs = f.read().strip().split(' ')
+
+    # 2) Load image & sanity-check
+    im = Image.open(args.image_file).convert('L')
+    w, h = im.size
+    if h != args.ich:
+        raise ValueError(f"Image height {h} ≠ ich {args.ich}")
+    count = w // args.icw
+    if count * args.icw != w:
+        raise ValueError(f"Image width {w} not a multiple of icw {args.icw}")
+    if len(glyphs) != count:
+        raise ValueError(f"{len(glyphs)} glyphs but {count} blocks in image")
+
+    # 3) Build mapping glyph → grid
+    mapping = {}
+    for i, glyph in enumerate(glyphs):
+        left = i * args.icw
+        block = im.crop((left, 0, left + args.icw, args.ich))
+        block = block.resize((args.obw, args.obh), Image.LANCZOS)
+        data = list(block.getdata())
+        bits = [1 if pix > args.threshold else 0 for pix in data]
+        grid = [bits[row*args.obw:(row+1)*args.obw] for row in range(args.obh)]
+        mapping[glyph] = grid
+
+    # 4) Write JSON manually so rows stay inline
+    with open(args.output, 'w', encoding='utf-8') as out:
+        out.write('{\n')
+        total = len(mapping)
+        for idx, (glyph, grid) in enumerate(mapping.items()):
+            # properly quote the glyph
+            key = json.dumps(glyph, ensure_ascii=False)
+            out.write(f'    {key}: [\n')
+            for ridx, row in enumerate(grid):
+                row_str = ','.join(str(bit) for bit in row)
+                comma = ',' if ridx < len(grid) - 1 else ''
+                out.write(f'        [{row_str}]{comma}\n')
+            out.write('    ]')
+            out.write(',\n' if idx < total - 1 else '\n')
+        out.write('}\n')
+
+if __name__ == '__main__':
+    main()

utils/mkrust.py

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+#!/usr/bin/env python3
+import json
+import unicodedata
+import argparse
+import sys
+
+def get_glyph_name(ch):
+    """
+    Return the official Unicode name of ch, or its codepoint if unnamed.
+    """
+    try:
+        return unicodedata.name(ch)
+    except ValueError:
+        # Fallback to codepoint string
+        return f"U+{ord(ch):04X}"
+
+def format_rust_array(matrix):
+    """
+    Given a 2D list of ints, return a Rust-style nested array string.
+    """
+    lines = []
+    for row in matrix:
+        # join numbers with commas, no spaces after commas to match example
+        line = "[" + ",".join(str(v) for v in row) + "],"
+        lines.append("        " + line)
+    return "\n".join(lines)
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Convert JSON glyph bitmaps to a Rust source file."
+    )
+    parser.add_argument("input_json", help="Path to input JSON file")
+    parser.add_argument("output_rs", help="Path to write Rust source file")
+    args = parser.parse_args()
+
+    # Load JSON
+    with open(args.input_json, "r", encoding="utf-8") as f:
+        data = json.load(f)
+
+    if not data:
+        print("No glyphs found in JSON.", file=sys.stderr)
+        sys.exit(1)
+
+    # Determine dimensions from first glyph
+    first_matrix = next(iter(data.values()))
+    rows = len(first_matrix)
+    cols = len(first_matrix[0]) if rows > 0 else 0
+
+    # Begin emitting Rust code
+    with open(args.output_rs, "w", encoding="utf-8") as out:
+        out.write("// This file was generated by mkrust.py\n")
+        out.write(f"pub const GLYPH_BITMAPS: &[(char, [[u8; {cols}]; {rows}])] = &[\n")
+
+        for ch, matrix in data.items():
+            name = get_glyph_name(ch)
+            # comment with the Unicode name
+            out.write(f"    // {name}\n")
+            out.write(f"    ('{ch}', [\n")
+            out.write(format_rust_array(matrix) + "\n")
+            out.write("    ]),\n\n")
+
+        out.write("];\n")
+
+if __name__ == "__main__":
+    main()