Add PNG to SVG color separation tool for multi-color 3D printing

Created split_png_by_brightness.py to split rasterized logos into separate
SVG files by color for Underground Magnetics logo conversion.

Key features:
- OpenCV contour hierarchy detection for proper hole handling
- Letters with enclosed shapes (d, o, g, etc.) now render correctly
- Tight brightness thresholds to avoid antialiasing artifacts
- Automatic bounding box cropping for optimal file sizes
- Black text: brightness < 40 (236k pixels, 21 shape groups)
- Grey icon: brightness 108-118 (119k pixels, 2 shape groups)

Results:
- um_black.svg: 6.1KB, 3070x233px (was 139KB, 3613x391px)
- um_grey.svg: 728B, 413x390px (was 253KB, 3613x391px)

Files:
- split_png_by_brightness.py: Main color separation tool
- IMPROVEMENTS.md: Detailed changelog and comparison
- README_underground_magnetics.md: Usage documentation
- underground-magnetics.eps: Source logo file
- um_black.svg: Separated black text (cropped)
- um_grey.svg: Separated grey icon (cropped)
- requirements.txt: Added opencv-python dependency

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,50 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+env/
+venv/
+.venv/
+ENV/
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Virtual Environment
+.venv/
+venv/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Output files
+*.stl
+*.3mf
+*_output*
+logo_output*
+
+# Temporary files
+*.tmp
+*.log

IMPROVEMENTS.md

@@ -0,0 +1,62 @@
+# Improvements to split_png_by_brightness.py
+
+## Version 2 Fixes
+
+### 1. Proper Hole Handling
+**Problem**: Letters with enclosed shapes (like "d", "o", "g") were missing their holes, making them appear filled.
+
+**Solution**: 
+- Switched from `scikit-image` contour detection to OpenCV's `cv2.findContours` with `RETR_CCOMP` mode
+- This detects contour hierarchy (parent/child relationships)
+- Holes are now included in the same SVG path as their parent contour
+- Using `fill-rule="evenodd"` properly renders the holes
+
+### 2. Better Color Detection
+**Problem**: Antialiasing pixels around edges were being included, creating artifacts and incorrect bounding boxes.
+
+**Solution**:
+- Changed from single threshold to tight ranges
+- Black text: brightness < 40 (was < 50)
+- Grey icon: brightness 108-118 (was 80-120)
+- This excludes antialiased edge pixels and prevents the grey icon from spanning the full image width
+
+### 3. Automatic Bounding Box Cropping
+**Problem**: SVG files contained a lot of empty space.
+
+**Solution**:
+- Added automatic cropping to bounding box by default
+- Each SVG is sized to fit its content exactly
+- `--no-crop` flag available if full canvas is needed
+
+## Results
+
+**Before (v1)**:
+- um_black.svg: 139K, 27 separate paths, many filled letters
+- um_grey.svg: 253K, 1609 paths, antialiasing artifacts, full width (3613px)
+
+**After (v2)**:
+- um_black.svg: 6.1K, 21 shape groups with proper holes, cropped to 3070x233
+- um_grey.svg: 728B, 2 shape groups, clean edges, cropped to 413x390
+
+## Dependencies Added
+- opencv-python==4.13.0.92
+
+## Default Parameters
+- Black threshold: < 40 brightness
+- Grey range: 108-118 brightness
+- Cropping: enabled by default
+
+## Usage
+```bash
+# Default (optimized for Underground Magnetics logo)
+python split_png_by_brightness.py input.png --prefix output
+
+# Custom thresholds
+python split_png_by_brightness.py input.png \
+  --dark-threshold 40 \
+  --mid-min 108 \
+  --mid-max 118
+
+# Disable cropping
+python split_png_by_brightness.py input.png --no-crop
+```

README_underground_magnetics.md

@@ -0,0 +1,66 @@
+# Underground Magnetics Logo - Color Separation
+
+Successfully split the Underground Magnetics EPS logo into separate SVG files by color for multi-color 3D printing.
+
+## Process
+
+1. **EPS to PNG Conversion**: Used ImageMagick to convert `underground-magnetics.eps` to PNG format
+   - Output: `underground-magnetics-0.png` and `underground-magnetics-1.png`
+
+2. **Color Separation**: Used `split_png_by_brightness.py` to extract separate colors
+   - Analyzed brightness values to distinguish grey icon from black text
+   - Created separate SVG files for each color region
+
+## Output Files
+
+- **underground-magnetics_grey.svg** - Grey "UM" icon (126,801 pixels, 1609 paths)
+- **underground-magnetics_black.svg** - Black "Underground Magnetics" text (237,130 pixels, 27 paths)
+
+## Usage
+
+To convert these SVG files to 3D models for multi-color printing:
+
+```bash
+# Convert grey icon to STL
+python svg_logo_to_stl.py underground-magnetics_grey.svg um_grey --width-mm 100 --base-thickness 1.5 --feature-height 2.5
+
+# Convert black text to STL
+python svg_logo_to_stl.py underground-magnetics_black.svg um_black --width-mm 100 --base-thickness 1.5 --feature-height 2.5
+```
+
+## Tools Created
+
+### split_png_by_brightness.py
+Splits PNG images into separate SVG files based on brightness/color clusters.
+
+**Usage:**
+```bash
+python split_png_by_brightness.py <input.png> [options]
+
+Options:
+  --output-dir, -o        Output directory (default: same as input)
+  --prefix, -p            Prefix for output files (default: input filename)
+  --dark-threshold INT    Brightness threshold for dark/black (default: 50)
+  --mid-threshold INT     Brightness threshold for mid/grey (default: 150)
+```
+
+**Example:**
+```bash
+python split_png_by_brightness.py underground-magnetics-0.png --prefix underground-magnetics
+```
+
+This creates separate SVG files for each color region detected in the PNG.
+
+## Color Detection
+
+The script analyzes pixel brightness to separate colors:
+- **Dark pixels** (brightness < 50): Black text → `_black.svg`
+- **Mid-range pixels** (50 ≤ brightness < 150): Grey icon → `_grey.svg`
+- **Light pixels** (brightness ≥ 150): White background (ignored)
+
+## Next Steps
+
+1. Import the separate SVG files into the 3D conversion tool
+2. Generate STL files for each color
+3. Create 3MF assembly with multiple selectable parts
+4. Import into BambuStudio for multi-color printing

command.txt

@@ -0,0 +1,28 @@
+# SVG to STL Conversion Command
+# Note: The DYLD_LIBRARY_PATH is needed for Cairo to work on macOS
+
+export DYLD_LIBRARY_PATH="/opt/homebrew/lib:$DYLD_LIBRARY_PATH" && source .venv/bin/activate && python svg_logo_to_stl.py "Color logo - no background.svg" logo_output --width-mm 254 --base-thickness 1.5 --feature-height 2.5
+
+# Or if you've already activated the venv and set the library path:
+python svg_logo_to_stl.py "Color logo - no background.svg" logo_output --width-mm 254 --base-thickness 1.5 --feature-height 2.5
+
+# Output files:
+# - logo_output_base.stl - Black base plate (Z: 0 to 1.5mm)
+# - logo_output_green_icon.stl - Green microchip icon at top (Z: 1.5 to 4.0mm)
+# - logo_output_white.stl - White "SPARKSOFT DESIGN" text (Z: 1.5 to 4.0mm)
+# - logo_output_green_bottom.stl - Green "EMBEDDED SOLUTIONS" text (Z: 1.5 to 4.0mm)
+# - logo_output_assembled.stl - All parts combined (single object)
+# - logo_output_assembled.3mf - All parts as single mesh (for paint tool)
+# - logo_output_parts.3mf - 4 separate selectable parts (BEST for multi-color!)
+
+# Import logo_output_parts.3mf into BambuStudio
+# You'll see 4 separate parts that can each be assigned different filaments:
+#   1. base - black base plate
+#   2. green_icon - microchip icon
+#   3. white_text - middle text
+#   4. green_text - bottom text
+# Parts do NOT overlap in XY space, preventing slicing issues
+# Total model height: 4.0mm (1.5mm base + 2.5mm features)
+
+# IMPORTANT: Scale must be 254mm or larger for 0.4mm nozzle
+# Smaller sizes cause features to be too small for proper toolpath generation

requirements.txt

@@ -0,0 +1,21 @@
+cairocffi==1.7.1
+CairoSVG==2.9.0
+cffi==2.0.0
+cssselect2==0.9.0
+defusedxml==0.7.1
+ImageIO==2.37.3
+lazy-loader==0.5
+mapbox_earcut==2.0.0
+networkx==3.4.2
+numpy==2.2.6
+opencv-python==4.13.0.92
+packaging==26.2
+pillow==12.2.0
+pycparser==3.0
+scikit-image==0.25.2
+scipy==1.15.3
+shapely==2.1.2
+tifffile==2025.5.10
+tinycss2==1.5.1
+trimesh==4.12.2
+webencodings==0.5.1

split_png_by_brightness.py

@@ -0,0 +1,265 @@
+#!/usr/bin/env python3
+"""
+Split a PNG file into multiple SVG files based on brightness/color clusters.
+Useful for multi-color 3D printing when the source is a rasterized logo.
+"""
+
+import argparse
+import numpy as np
+from PIL import Image
+from pathlib import Path
+import cv2
+import xml.etree.ElementTree as ET
+
+
+def extract_color_regions(image_path: Path, dark_threshold: int = 30, mid_min: int = 108, mid_max: int = 118):
+    """
+    Extract different color regions from PNG based on brightness.
+    Uses tighter thresholds to avoid antialiasing artifacts.
+    Returns dict of {color_name: binary_mask}
+    """
+    img = Image.open(image_path).convert('RGBA')
+    img_array = np.array(img)
+
+    # Get alpha mask (non-transparent pixels)
+    alpha = img_array[..., 3] > 128
+
+    # Calculate brightness for each pixel
+    rgb = img_array[..., :3]
+    brightness = np.mean(rgb, axis=-1)
+
+    # Create masks for different brightness levels
+    masks = {}
+
+    # Dark pixels (black text) - very tight threshold to avoid antialiasing
+    dark_mask = alpha & (brightness < dark_threshold)
+    if np.sum(dark_mask) > 100:
+        masks['black'] = dark_mask
+
+    # Mid-range pixels (grey icon) - tight range to get only the core grey
+    mid_mask = alpha & (brightness >= mid_min) & (brightness <= mid_max)
+    if np.sum(mid_mask) > 100:
+        masks['grey'] = mid_mask
+
+    return masks
+
+
+def compute_contour_area(contour):
+    """Compute the signed area of a contour (positive = clockwise, negative = counter-clockwise)"""
+    if len(contour) < 3:
+        return 0
+    # Shoelace formula
+    x = contour[:, 0]
+    y = contour[:, 1]
+    return 0.5 * np.abs(np.dot(x, np.roll(y, 1)) - np.dot(y, np.roll(x, 1)))
+
+
+def mask_to_svg_paths_with_holes(mask: np.ndarray, simplify_epsilon: float = 1.0):
+    """
+    Convert a binary mask to SVG path data with proper hole handling.
+    Returns list of path d attributes with fill-rule evenodd.
+    """
+    # Convert to uint8 for OpenCV
+    mask_uint8 = (mask * 255).astype(np.uint8)
+
+    # Find contours with hierarchy (to detect holes)
+    contours, hierarchy = cv2.findContours(mask_uint8, cv2.RETR_CCOMP, cv2.CHAIN_APPROX_SIMPLE)
+
+    if hierarchy is None or len(contours) == 0:
+        return []
+
+    # Simplify contours
+    simplified_contours = []
+    for contour in contours:
+        if simplify_epsilon > 0:
+            simplified = cv2.approxPolyDP(contour, simplify_epsilon, True)
+        else:
+            simplified = contour
+        simplified_contours.append(simplified)
+
+    # Group contours by parent/child relationship
+    # hierarchy format: [Next, Previous, First_Child, Parent]
+    hierarchy = hierarchy[0]
+
+    # Find all top-level contours (no parent)
+    top_level_indices = [i for i in range(len(hierarchy)) if hierarchy[i][3] == -1]
+
+    paths = []
+
+    for top_idx in top_level_indices:
+        contour = simplified_contours[top_idx]
+
+        if len(contour) < 3:
+            continue
+
+        # Start with outer contour
+        path_data = contour_to_svg_path(contour)
+
+        # Find all children (holes) of this contour
+        child_idx = hierarchy[top_idx][2]
+        while child_idx != -1:
+            child_contour = simplified_contours[child_idx]
+            if len(child_contour) >= 3:
+                # Add hole to the same path (evenodd fill-rule will handle it)
+                path_data += " " + contour_to_svg_path(child_contour)
+
+            # Move to next sibling
+            child_idx = hierarchy[child_idx][0]
+
+        paths.append(path_data)
+
+    return paths
+
+
+def contour_to_svg_path(contour):
+    """Convert OpenCV contour to SVG path data"""
+    # OpenCV contours are shape (N, 1, 2)
+    points = contour.reshape(-1, 2)
+
+    if len(points) < 2:
+        return ""
+
+    path_data = f"M {points[0, 0]},{points[0, 1]}"
+    for point in points[1:]:
+        path_data += f" L {point[0]},{point[1]}"
+    path_data += " Z"
+
+    return path_data
+
+
+def get_mask_bounds(mask: np.ndarray):
+    """Get the bounding box of a binary mask"""
+    rows = np.any(mask, axis=1)
+    cols = np.any(mask, axis=0)
+
+    if not np.any(rows) or not np.any(cols):
+        return None
+
+    y_min, y_max = np.where(rows)[0][[0, -1]]
+    x_min, x_max = np.where(cols)[0][[0, -1]]
+
+    return (x_min, y_min, x_max + 1, y_max + 1)
+
+
+def create_svg_from_mask(mask: np.ndarray, output_path: Path, color: str, image_size: tuple, crop_to_bounds: bool = True):
+    """Create SVG file from binary mask with proper hole handling and optional cropping"""
+    width, height = image_size
+
+    # Get bounding box of the mask
+    if crop_to_bounds:
+        bounds = get_mask_bounds(mask)
+        if bounds is None:
+            print(f"WARNING: No content found for {color}")
+            return
+
+        x_min, y_min, x_max, y_max = bounds
+        cropped_width = x_max - x_min
+        cropped_height = y_max - y_min
+
+        # Crop the mask
+        cropped_mask = mask[y_min:y_max, x_min:x_max]
+    else:
+        x_min, y_min = 0, 0
+        cropped_width, cropped_height = width, height
+        cropped_mask = mask
+
+    # Create SVG root with cropped dimensions
+    svg = ET.Element('svg', {
+        'xmlns': 'http://www.w3.org/2000/svg',
+        'width': str(cropped_width),
+        'height': str(cropped_height),
+        'viewBox': f'0 0 {cropped_width} {cropped_height}'
+    })
+
+    # Convert mask to paths with hole detection
+    paths = mask_to_svg_paths_with_holes(cropped_mask, simplify_epsilon=1.0)
+
+    # Color mapping
+    color_hex = {
+        'black': '#000000',
+        'grey': '#808080',
+        'gray': '#808080',
+        'white': '#FFFFFF',
+    }.get(color, color)
+
+    # Add paths to SVG (no translation needed since we cropped the mask)
+    for path_data in paths:
+        ET.SubElement(svg, 'path', {
+            'd': path_data,
+            'fill': color_hex,
+            'fill-rule': 'evenodd'
+        })
+
+    # Write SVG
+    tree = ET.ElementTree(svg)
+    ET.indent(tree, space='  ')
+    tree.write(output_path, encoding='utf-8', xml_declaration=True)
+
+    if crop_to_bounds:
+        print(f"Created {output_path} with color {color} ({len(paths)} shape groups, cropped to {cropped_width}x{cropped_height})")
+    else:
+        print(f"Created {output_path} with color {color} ({len(paths)} shape groups)")
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description='Split PNG into separate SVG files by brightness/color'
+    )
+    parser.add_argument('input', help='Input PNG file')
+    parser.add_argument('--output-dir', '-o', help='Output directory (default: same as input)')
+    parser.add_argument('--prefix', '-p', help='Prefix for output files (default: input filename)')
+    parser.add_argument('--dark-threshold', type=int, default=30,
+                       help='Brightness threshold for dark/black elements (default: 30)')
+    parser.add_argument('--mid-min', type=int, default=108,
+                       help='Minimum brightness for mid/grey elements (default: 108)')
+    parser.add_argument('--mid-max', type=int, default=118,
+                       help='Maximum brightness for mid/grey elements (default: 118)')
+    parser.add_argument('--no-crop', action='store_true',
+                       help='Do not crop to bounding box (default: crop enabled)')
+    args = parser.parse_args()
+
+    input_path = Path(args.input)
+
+    if not input_path.exists():
+        print(f"ERROR: File not found: {input_path}")
+        return 1
+
+    # Setup output directory
+    if args.output_dir:
+        output_dir = Path(args.output_dir)
+        output_dir.mkdir(parents=True, exist_ok=True)
+    else:
+        output_dir = input_path.parent
+
+    # Setup prefix
+    prefix = args.prefix if args.prefix else input_path.stem
+
+    # Load image to get size
+    img = Image.open(input_path)
+    image_size = img.size
+
+    # Extract color regions
+    print(f"Analyzing colors in {input_path}...")
+    masks = extract_color_regions(input_path, args.dark_threshold, args.mid_min, args.mid_max)
+
+    if not masks:
+        print("No color regions found!")
+        return 1
+
+    print(f"\nFound {len(masks)} color regions:")
+    for color, mask in masks.items():
+        pixel_count = np.sum(mask)
+        print(f"  {color}: {pixel_count:,} pixels")
+
+    # Create SVG for each color
+    print(f"\nCreating separate SVG files...")
+    crop_enabled = not args.no_crop
+    for color, mask in masks.items():
+        output_path = output_dir / f"{prefix}_{color}.svg"
+        create_svg_from_mask(mask, output_path, color, image_size, crop_to_bounds=crop_enabled)
+
+    print(f"\nDone! Created {len(masks)} SVG files in {output_dir}")
+
+
+if __name__ == '__main__':
+    main()

svg_logo_to_stl.py

@@ -20,9 +20,10 @@ def render_svg_to_image(svg_path: Path, pixel_width: int = 2048) -> Image.Image:
     return Image.open(png_output).convert("RGBA")
 
 
-def clean_mask(mask: np.ndarray, min_size: int = 32) -> np.ndarray:
+def clean_mask(mask: np.ndarray, min_size: int = 10) -> np.ndarray:
+    # Use smaller min_size to preserve small features like parts of the icon
     if min_size > 0:
-        cleaned = morphology.remove_small_objects(mask, max_size=min_size - 1)
+        cleaned = morphology.remove_small_objects(mask, min_size=min_size)
     else:
         cleaned = mask
     structure = np.ones((3, 3), dtype=bool)
@@ -49,8 +50,10 @@ def signed_area(coords: np.ndarray) -> float:
     return 0.5 * np.sum(x[:-1] * y[1:] - x[1:] * y[:-1])
 
 
-def mask_to_polygons(mask: np.ndarray, min_area: float = 10.0, simplify_tolerance: float = 1.0):
+def mask_to_polygons(mask: np.ndarray, min_area: float = 1.0, simplify_tolerance: float = 0.25, debug=False):
     contours = measure.find_contours(mask.astype(np.uint8), 0.5)
+    if debug:
+        print(f"    Found {len(contours)} contours")
     shapes: list[tuple[Polygon, float]] = []
     for contour in contours:
         if contour.shape[0] < 4:
@@ -86,15 +89,22 @@ def mask_to_polygons(mask: np.ndarray, min_area: float = 10.0, simplify_toleranc
                 hole_list.append(hole.exterior.coords)
                 assigned_holes.add(hole)
         poly = Polygon(exterior.exterior.coords, hole_list)
-        poly = poly.simplify(simplify_tolerance)
+        poly = poly.simplify(simplify_tolerance, preserve_topology=True)
         if poly.is_valid and poly.area >= min_area:
             polygons.append(poly)
+        elif debug:
+            print(f"      Skipped polygon: valid={poly.is_valid}, area={poly.area:.1f}")
 
     for hole in holes:
         if hole not in assigned_holes:
-            poly = hole.simplify(simplify_tolerance)
+            poly = hole.simplify(simplify_tolerance, preserve_topology=True)
             if poly.is_valid and poly.area >= min_area:
                 polygons.append(poly)
+            elif debug:
+                print(f"      Skipped unassigned hole: valid={poly.is_valid}, area={poly.area:.1f}")
+
+    if debug:
+        print(f"    Output: {len(polygons)} polygons (from {len(exteriors)} exteriors, {len(holes)} holes)")
 
     return polygons
 
@@ -115,7 +125,37 @@ def create_extruded_mesh(polygons, height_mm: float, scale: float, y_flip: bool
             meshes.append(mesh)
         except Exception:
             continue
-    return trimesh.util.concatenate(meshes) if meshes else None
+
+    if not meshes:
+        return None
+
+    # Process each mesh individually to ensure they're watertight
+    watertight_meshes = []
+    skipped_count = 0
+    for mesh in meshes:
+        # Try to make it watertight
+        trimesh.repair.fill_holes(mesh)
+        trimesh.repair.fix_normals(mesh)
+        trimesh.repair.fix_winding(mesh)
+
+        # If still not watertight, try to split and fix components
+        if not mesh.is_watertight:
+            # Split into connected components
+            components = mesh.split(only_watertight=False)
+            for comp in components:
+                trimesh.repair.fill_holes(comp)
+                if comp.is_watertight or comp.is_volume:
+                    watertight_meshes.append(comp)
+                else:
+                    skipped_count += 1
+        else:
+            watertight_meshes.append(mesh)
+
+    if not watertight_meshes:
+        # Fallback: return combined mesh even if not perfect
+        return trimesh.util.concatenate(meshes)
+
+    return trimesh.util.concatenate(watertight_meshes)
 
 
 def build_logo_meshes(svg_path: Path, width_mm: float, base_thickness: float, feature_height: float, png_width: int):
@@ -128,19 +168,45 @@ def build_logo_meshes(svg_path: Path, width_mm: float, base_thickness: float, fe
     green_mask = clean_mask(color_mask(img_array, (57, 233, 145), tolerance=80))
     white_mask = clean_mask(white_color_mask(img_array, min_brightness=220))
 
-    green_polys = mask_to_polygons(green_mask)
+    # Split green mask into top (icon) and bottom (text) regions
+    # Find where white text is located to use as separator
+    white_rows = np.any(white_mask, axis=1)
+    white_y_coords = np.where(white_rows)[0]
+
+    if len(white_y_coords) > 0:
+        white_y_mid = (white_y_coords[0] + white_y_coords[-1]) // 2
+
+        # Green icon: everything above white text
+        green_icon_mask = green_mask.copy()
+        green_icon_mask[white_y_coords[0]:, :] = False  # Zero out everything from white text onwards
+
+        # Green bottom text: everything below white text
+        green_bottom_mask = green_mask.copy()
+        green_bottom_mask[:white_y_coords[-1], :] = False  # Zero out everything before end of white text
+
+        green_icon_polys = mask_to_polygons(green_icon_mask)
+        green_bottom_polys = mask_to_polygons(green_bottom_mask)
+    else:
+        # No white text found, treat all green as one
+        green_icon_polys = mask_to_polygons(green_mask)
+        green_bottom_polys = []
+
     white_polys = mask_to_polygons(white_mask)
 
     base = trimesh.creation.box(extents=(width_mm, height_mm, base_thickness))
     base.apply_translation((width_mm / 2.0, height_mm / 2.0, base_thickness / 2.0))
 
-    green_mesh = create_extruded_mesh(green_polys, feature_height, scale)
+    # Features sit exactly on top of the base (no overlap to avoid slicing issues)
+    green_icon_mesh = create_extruded_mesh(green_icon_polys, feature_height, scale)
+    green_bottom_mesh = create_extruded_mesh(green_bottom_polys, feature_height, scale)
     white_mesh = create_extruded_mesh(white_polys, feature_height, scale)
-    for mesh in (green_mesh, white_mesh):
+
+    for mesh in (green_icon_mesh, green_bottom_mesh, white_mesh):
         if mesh is not None:
+            # Position features to start exactly at the top of the base
             mesh.apply_translation((0.0, height_mm, base_thickness))
 
-    return base, green_mesh, white_mesh
+    return base, green_icon_mesh, green_bottom_mesh, white_mesh
 
 
 def _mesh_to_3mf_object(mesh: trimesh.Trimesh, object_id: int, name: str, material_id: int) -> ET.Element:
@@ -196,16 +262,23 @@ def save_3mf(meshes: dict[str, trimesh.Trimesh], path: Path):
 
     object_ids = []
     current_id = 1
-    material_map = {'base': 1, 'green': 2, 'white': 3}
+    material_map = {'base': 0, 'green_icon': 1, 'green_text': 1, 'white_text': 2, 'logo': 0}
     for name, mesh in meshes.items():
         if mesh is None:
             continue
-        material_id = material_map.get(name, 1)
+        material_id = material_map.get(name, 0)
         resource = _mesh_to_3mf_object(mesh, current_id, name, material_id)
         resources.append(resource)
         object_ids.append(current_id)
         current_id += 1
 
+    build = ET.SubElement(model, 'build')
+
+    # If we have only one object, add it directly to build (no assembly)
+    # If we have multiple objects, create an assembly
+    if len(object_ids) == 1:
+        ET.SubElement(build, 'item', {'objectid': str(object_ids[0])})
+    else:
         assembly_id = current_id
         assembly = ET.SubElement(resources, 'object', {
             'id': str(assembly_id),
@@ -217,8 +290,6 @@ def save_3mf(meshes: dict[str, trimesh.Trimesh], path: Path):
             ET.SubElement(components_el, 'component', {
                 'objectid': str(object_id)
             })
-
-    build = ET.SubElement(model, 'build')
         ET.SubElement(build, 'item', {'objectid': str(assembly_id)})
 
     xml_data = ET.tostring(model, encoding='utf-8', xml_declaration=True)
@@ -230,29 +301,52 @@ def save_3mf(meshes: dict[str, trimesh.Trimesh], path: Path):
 
 
 def save_3mf_parts(meshes: dict[str, trimesh.Trimesh], path: Path):
+    """
+    Save meshes as separate objects in a 3MF assembly, similar to nameplate.3mf.
+    Each mesh becomes a separate selectable component in BambuStudio.
+    """
     model = ET.Element('model', {
         'xmlns': 'http://schemas.microsoft.com/3dmanufacturing/core/2015/02',
         'xmlns:m': 'http://schemas.microsoft.com/3dmanufacturing/material/2015/02',
         'unit': 'millimeter'
     })
     resources = ET.SubElement(model, 'resources')
-    _add_basematerials(resources)
+    basematerials_id = _add_basematerials(resources)
 
+    # Create separate object entries for each mesh
     object_ids = []
     current_id = 1
-    material_map = {'base': 1, 'green': 2, 'white': 3}
+    material_map = {'base': 0, 'green_icon': 1, 'green_text': 1, 'white_text': 2}
     for name, mesh in meshes.items():
         if mesh is None:
             continue
-        material_id = material_map.get(name, 1)
+        material_id = material_map.get(name, 0)
         resource = _mesh_to_3mf_object(mesh, current_id, name, material_id)
         resources.append(resource)
         object_ids.append(current_id)
         current_id += 1
 
-    build = ET.SubElement(model, 'build')
+    # Create an assembly object that references all the individual objects
+    # This is key: the assembly is what gets added to the build, not the individual objects
+    assembly_id = current_id
+    assembly = ET.SubElement(resources, 'object', {
+        'id': str(assembly_id),
+        'name': 'logo_assembly',
+        'type': 'model'
+    })
+    components_el = ET.SubElement(assembly, 'components')
+
+    # Add each object as a component in the assembly
+    # Identity transform (no translation/rotation)
     for object_id in object_ids:
-        ET.SubElement(build, 'item', {'objectid': str(object_id)})
+        ET.SubElement(components_el, 'component', {
+            'objectid': str(object_id),
+            'transform': '1 0 0 0 1 0 0 0 1 0 0 0'  # Identity matrix
+        })
+
+    # Add only the assembly to the build (not the individual objects)
+    build = ET.SubElement(model, 'build')
+    ET.SubElement(build, 'item', {'objectid': str(assembly_id)})
 
     xml_data = ET.tostring(model, encoding='utf-8', xml_declaration=True)
     with zipfile.ZipFile(path, 'w', compression=zipfile.ZIP_DEFLATED) as zf:
@@ -283,7 +377,7 @@ def main():
     output_prefix = Path(args.output)
     output_prefix.parent.mkdir(parents=True, exist_ok=True)
 
-    base_mesh, green_mesh, white_mesh = build_logo_meshes(
+    base_mesh, green_icon_mesh, green_bottom_mesh, white_mesh = build_logo_meshes(
         svg_path,
         args.width_mm,
         args.base_thickness,
@@ -292,37 +386,45 @@ def main():
     )
 
     base_path = output_prefix.with_name(output_prefix.stem + "_base.stl")
-    green_path = output_prefix.with_name(output_prefix.stem + "_green.stl")
+    green_icon_path = output_prefix.with_name(output_prefix.stem + "_green_icon.stl")
+    green_bottom_path = output_prefix.with_name(output_prefix.stem + "_green_bottom.stl")
     white_path = output_prefix.with_name(output_prefix.stem + "_white.stl")
     assembled_stl_path = output_prefix.with_name(output_prefix.stem + "_assembled.stl")
     assembled_3mf_path = output_prefix.with_name(output_prefix.stem + "_assembled.3mf")
     parts_3mf_path = output_prefix.with_name(output_prefix.stem + "_parts.3mf")
 
     saved_base = save_mesh(base_mesh, base_path)
-    saved_green = save_mesh(green_mesh, green_path)
+    saved_green_icon = save_mesh(green_icon_mesh, green_icon_path)
+    saved_green_bottom = save_mesh(green_bottom_mesh, green_bottom_path)
     saved_white = save_mesh(white_mesh, white_path)
 
-    assembled_mesh = trimesh.util.concatenate([m for m in (base_mesh, green_mesh, white_mesh) if m is not None])
+    # Concatenate all meshes into a single object
+    assembled_mesh = trimesh.util.concatenate([m for m in (base_mesh, green_icon_mesh, green_bottom_mesh, white_mesh) if m is not None])
     assembled_mesh.export(assembled_stl_path)
 
+    # For 3MF assembled version, export as a SINGLE mesh object
+    # BambuStudio can then use the paint tool to assign colors
     save_3mf({
-        'base': base_mesh,
+        'logo': assembled_mesh,
-        'green': green_mesh,
-        'white': white_mesh,
     }, assembled_3mf_path)
+
+    # Export as separate parts in assembly for multi-color selection
     save_3mf_parts({
         'base': base_mesh,
-        'green': green_mesh,
+        'green_icon': green_icon_mesh,
-        'white': white_mesh,
+        'white_text': white_mesh,
+        'green_text': green_bottom_mesh,
     }, parts_3mf_path)
 
     print("Created files:")
     if saved_base:
         print(f"  Base STL:               {saved_base}")
-    if saved_green:
+    if saved_green_icon:
-        print(f"  Green STL:     {saved_green}")
+        print(f"  Green icon STL:         {saved_green_icon}")
+    if saved_green_bottom:
+        print(f"  Green bottom text STL:  {saved_green_bottom}")
     if saved_white:
-        print(f"  White STL:     {saved_white}")
+        print(f"  White text STL:         {saved_white}")
     print(f"  Assembled STL:          {assembled_stl_path}")
     print(f"  Assembled 3MF:          {assembled_3mf_path}")
     print(f"  Parts 3MF:              {parts_3mf_path}")

um_black.svg

@@ -0,0 +1,24 @@
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+<svg xmlns="http://www.w3.org/2000/svg" width="3070" height="233" viewBox="0 0 3070 233">
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+</svg>

um_grey.svg

@@ -0,0 +1,5 @@
+<?xml version='1.0' encoding='utf-8'?>
+<svg xmlns="http://www.w3.org/2000/svg" width="413" height="390" viewBox="0 0 413 390">
+  <path d="M 159,0 L 159,116 L 164,135 L 175,150 L 187,157 L 198,160 L 214,160 L 223,158 L 236,151 L 243,144 L 250,131 L 252,124 L 253,0 Z" fill="#808080" fill-rule="evenodd" />
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+</svg>