Files

Brent Perteet 2719ec244d 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>

2026-05-31 09:51:24 -05:00

2.3 KiB

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Underground Magnetics Logo - Color Separation

Successfully split the Underground Magnetics EPS logo into separate SVG files by color for multi-color 3D printing.

Process

EPS to PNG Conversion: Used ImageMagick to convert underground-magnetics.eps to PNG format
- Output: underground-magnetics-0.png and underground-magnetics-1.png
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:

# 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:

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:

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

Import the separate SVG files into the 3D conversion tool
Generate STL files for each color
Create 3MF assembly with multiple selectable parts
Import into BambuStudio for multi-color printing

2.3 KiB Raw Blame History