TTF build using fontforge

OTFbuild/bitmap_tracer.py

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+"""
+Convert 1-bit bitmap arrays to TrueType quadratic outlines.
+
+Each set pixel becomes part of a rectangle contour drawn clockwise.
+Adjacent identical horizontal runs are merged vertically into rectangles.
+
+Scale: x_left = col * SCALE, y_top = (BASELINE_ROW - row) * SCALE
+where BASELINE_ROW = 16 (ascent in pixels).
+"""
+
+from typing import Dict, List, Tuple
+
+import sheet_config as SC
+
+SCALE = SC.SCALE
+BASELINE_ROW = 16  # pixels from top to baseline
+
+
+def trace_bitmap(bitmap, glyph_width_px):
+    """
+    Convert a bitmap to a list of rectangle contours.
+
+    Each rectangle is ((x0, y0), (x1, y1)) in font units, where:
+    - (x0, y0) is bottom-left
+    - (x1, y1) is top-right
+
+    Returns list of (x0, y0, x1, y1) tuples representing rectangles.
+    """
+    if not bitmap or not bitmap[0]:
+        return []
+
+    h = len(bitmap)
+    w = len(bitmap[0])
+
+    # Step 1: Find horizontal runs per row
+    runs = []  # list of (row, col_start, col_end)
+    for row in range(h):
+        col = 0
+        while col < w:
+            if bitmap[row][col]:
+                start = col
+                while col < w and bitmap[row][col]:
+                    col += 1
+                runs.append((row, start, col))
+            else:
+                col += 1
+
+    # Step 2: Merge vertically adjacent identical runs into rectangles
+    rects = []  # (row_start, row_end, col_start, col_end)
+    used = [False] * len(runs)
+
+    for i, (row, cs, ce) in enumerate(runs):
+        if used[i]:
+            continue
+        # Try to extend this run downward
+        row_end = row + 1
+        j = i + 1
+        while j < len(runs):
+            r2, cs2, ce2 = runs[j]
+            if r2 > row_end:
+                break
+            if r2 == row_end and cs2 == cs and ce2 == ce and not used[j]:
+                used[j] = True
+                row_end = r2 + 1
+            j += 1
+        rects.append((row, row_end, cs, ce))
+
+    # Step 3: Convert to font coordinates
+    contours = []
+    for row_start, row_end, col_start, col_end in rects:
+        x0 = col_start * SCALE
+        x1 = col_end * SCALE
+        y_top = (BASELINE_ROW - row_start) * SCALE
+        y_bottom = (BASELINE_ROW - row_end) * SCALE
+        contours.append((x0, y_bottom, x1, y_top))
+
+    return contours
+
+
+def draw_glyph_to_pen(contours, pen):
+    """
+    Draw rectangle contours to a TTGlyphPen or similar pen.
+    Each rectangle is drawn as a clockwise closed contour (4 on-curve points).
+    """
+    for x0, y0, x1, y1 in contours:
+        # Clockwise: bottom-left -> top-left -> top-right -> bottom-right
+        pen.moveTo((x0, y0))
+        pen.lineTo((x0, y1))
+        pen.lineTo((x1, y1))
+        pen.lineTo((x1, y0))
+        pen.closePath()