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RasterCarve is a small, open-source Python utility that turns bitmap images into raster-engraving G-code. It samples an image line by line, maps brightness to cutting depth, and produces a toolpath that a compatible three-axis CNC router can execute.
It is useful for grayscale artwork, photographs, and tonal engravings—but it is not a CNC controller, a complete CAM package, or an automatic raster-to-SVG converter. You must still prepare the image, verify the G-code, configure the machine, and choose safe tooling and cutting conditions.
What RasterCarve does
RasterCarve belongs to the raster-engraving category. Instead of identifying clean outlines, it sweeps a cutter across the work in successive passes. Darker image areas are normally mapped to deeper cuts, while lighter areas receive shallower cuts. The result is a physical interpretation of image brightness through depth and tool geometry.
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- Start with a bitmap such as PNG or another format supported through OpenCV.
- Crop, resize, grayscale, and adjust the image for engraving.
- RasterCarve samples the image along a series of lines.
- Pixel intensity is converted into cutting depth.
- The program writes G-code to standard output.
- You load that G-code into a suitable CNC sender or controller.
- The router engraves the image row by row.
The project is attributed to Franklin Wei, is distributed under the GPLv2-or-later license, and is available as a Python package on PyPI. The latest release shown on the package page is version 1.0.8, uploaded on March 25, 2020. That makes RasterCarve a useful but relatively old project; do not assume that it is actively maintained or that every modern Python version, operating system, or controller has been tested.
The package description also references a hosted version at rastercarve.live. Its current uptime, maintenance, privacy practices, and security were not independently verified, so local installation is the more transparent option for sensitive images.
Raster engraving is not vector cutting
This distinction determines whether RasterCarve is the right tool.
- Raster engraving follows rows or angled passes across an image. Brightness controls depth or another engraving parameter.
- Vector cutting follows defined lines, curves, outlines, pockets, or profiles.
- RasterCarve primarily generates depth-varying raster toolpaths. It does not automatically create clean SVG or DXF outlines from a photograph.
For a portrait, textured illustration, or grayscale painting that should become a tonal engraving, RasterCarve may fit. For lettering, a logo outline, contour cutting, or profile machining, you generally need vectorization and conventional CAM. WinTopo, for example, is designed to convert raster artwork into vector data for CAD, GIS, and CNC workflows; that is a different job.
Install RasterCarve
The published package metadata requires Python 3.6 or newer. Because that requirement comes from a 2020 release, treat it as package metadata rather than proof of compatibility with every current Python release.
A virtual environment keeps RasterCarve separate from other Python projects:
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python -m venv .venvActivate it in Windows PowerShell:
.venvScriptsActivate.ps1Or on macOS and Linux:
source .venv/bin/activateInstall the package and inspect the locally installed command:
python -m pip install rastercarve
rastercarve --version
rastercarve -hRunning the help command before processing an image matters. It confirms the options supported by the version you actually installed, including the units and semantics of settings whose behavior may depend on the release.
Generate your first toolpath
The documented basic example is:
rastercarve --width 10 examples/test.png > out.ncThis asks RasterCarve to make the image 10 inches wide and redirects the generated G-code into out.nc. The > character is shell redirection; RasterCarve writes the toolpath to standard output rather than choosing the output filename itself.
You must provide exactly one physical dimension:
rastercarve --height 8 photo.png > photo.ncRasterCarve calculates the other dimension from the image aspect ratio. Use clear filenames that preserve the source image and identify the intended size, for example portrait-10in.nc. Do not overwrite the original image or an earlier verified toolpath.
Important command-line options
| Option | Purpose |
|---|---|
--width / --height |
Sets the physical output size; supply one, not both. |
-f |
Cutting feed rate. |
-p |
Plunge rate. |
--rapid |
Rapid-traverse speed. |
-z |
Safe Z height used while moving between engraving areas. |
--end-z |
End or traverse Z setting; confirm its exact meaning with the installed version’s help output. |
-t |
V-bit angle used in depth and width calculations. |
-d |
Maximum cutting depth. |
-a |
Raster-line angle. |
-s |
Stepover between adjacent raster passes. |
-r |
Linear resolution, or distance between successive G-code points. |
--dots |
Alternate dot-oriented rendering mode. Confirm its machine behavior locally. |
--no-line-numbers |
Omits line numbers. The package specifically warns that this can be dangerous on ShopBot machines. |
--preamble / --epilogue |
Adds machine-specific G-code before or after the toolpath. |
--json |
Writes statistics to a JSON destination. |
--debug / -q |
Enables diagnostics or suppresses progress and statistics output. |
Published example values—including a 30-degree V-bit, 0.080-inch maximum depth, 100 inches per minute feed, and 30 inches per minute plunge—are example settings, not universal recommendations. A safe value depends on the machine, cutter, material, workholding, spindle, and controller.
What the published example reveals
RasterCarve’s example uses a 512 × 512 pixel image and produces a 10 × 10-inch output. Its reported statistics include:
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- Maximum line depth: 0.080 inch
- Maximum line width: 0.043 inch with a 30-degree V-bit
- Line spacing: 0.047 inch
- Line angle: 22.5 degrees
- Number of lines: 277
- Input resolution: 51.2 PPI
- Output resolution: 100 PPI
- Toolpath length: 2,202.6 inches
- Estimated machining time: 1,351.2 seconds, or about 22.5 minutes
These figures are specific to the package’s example. They demonstrate why a small-looking image can produce a surprisingly long job: physical size, image resolution, stepover, line angle, and point spacing all affect file size and machining time.
Prepare the image before generating G-code
Image preparation often matters more than the conversion itself. A photograph that looks good on a screen may contain too little tonal separation—or too much fine detail—to carve cleanly.
- Crop the composition. Remove empty areas and place the subject within the intended stock dimensions.
- Convert to grayscale. Color information must ultimately become a depth or intensity value.
- Adjust contrast. Separate the subject from its background without crushing every midtone into black or white.
- Reduce noise. Small photographic artifacts can become unnecessary tool motion.
- Resize sensibly. More pixels do not automatically create more visible detail in wood or plastic.
- Check the tonal direction. If the subject and background appear reversed, invert the grayscale image before generating the path.
- Save a lossless copy. PNG is a practical working format.
The normal project description maps darker pixels to deeper cuts, but preview the result rather than relying only on the source photograph. The final appearance also depends on cutter angle, material, depth, stepover, lighting, and surface finish.
Check compatibility before running the file
G-code is not a universal guarantee of compatibility. Controllers differ in dialect, units, coordinate conventions, supported commands, required startup code, and expectations about line numbers.
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- Open the generated file in a simulator or G-code previewer.
- Confirm units, axis directions, origin, maximum dimensions, and safe-Z behavior.
- Inspect the first and last several lines for appropriate startup and shutdown commands.
- Use the correct preamble and epilogue for the target machine when required.
- Run an air cut above the stock with the spindle disabled.
- Test the complete setup on scrap material.
The PyPI documentation points to a standalone previewer at github.com/built1n/rastercarve-preview. Its current availability and maintenance should be confirmed before relying on it.
Set up the CNC machine
The project documentation describes this high-level workflow:
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- Install the correct engraving bit.
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- Zero X and Y at the top-left corner of the intended image area, unless your controller and workflow use another verified origin.
- Check that the lower-right extent remains inside the machine’s travel.
- Zero Z on the material’s top surface.
- Load the verified toolpath and monitor the first pass.
An engraving bit is preferred in the project documentation, although ordinary V-bits may produce acceptable results. The tool angle used during generation should match the actual cutter geometry. A nominal bit label is not always enough; verify the manufacturer’s specification when possible.
The project author reported the best results with MDF, while plywood and ordinary lumber were more prone to chipping and plastics could melt and stick to the cutter. Those are project-specific observations, not universal material tests. Start with scrap, use firm workholding, and choose feeds, speeds, depth, and chip evacuation for the particular material.
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Common problems and fixes
The physical size is wrong
If the carving is stretched, compressed, or larger than the stock, check the supplied width or height, controller units, and coordinate scaling. Recalculate machine travel before re-zeroing and running another file.
The image is inverted
If the background is deep and the subject is shallow, invert the grayscale source, regenerate the G-code, and test on scrap. Do not assume that a bright area on the monitor will look bright on the finished material.
The job takes too long
Fine stepover, excessive image resolution, a large physical output, and angled raster passes can create long toolpaths. Compare the statistics, simplify the image, reduce unnecessary resolution, or increase stepover cautiously while preserving the detail the material can reproduce.
Edges chip or details look fuzzy
Possible causes include grain direction, a dull cutter, excessive depth, unsuitable stepover, weak workholding, or an image containing more detail than the material can hold. Try a sharper tool, shallower cuts, stronger contrast, and a more stable test material.
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Plastic melts onto the bit
Heat buildup and unsuitable cutting conditions can smear plastic. Stop rather than allowing buildup to continue, then test feed, spindle speed, depth, and chip evacuation on scrap for the specific plastic and cutter.
The controller rejects the file
Check for dialect, units, unsupported commands, missing preamble, line-number requirements, and coordinate conventions. Use the installed help output, add machine-specific startup or shutdown code, preview the path, and perform an air cut. Generic G-code should never be assumed to work unchanged on every machine.
The engraving width does not match expectations
A mismatch between the actual cutter angle and the -t value changes the relationship between depth and engraved width. Verify the bit angle and regenerate the path.
RasterCarve compared with alternatives
Easel
Easel is a broader browser-based CNC design and toolpath environment. Its official page showed a free plan, Easel Starter at $8 per month or $72 per year, and Easel Pro at $24 per month or $216 per year during the available August 2026 pricing check. Prices, quotas, and features can change.
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Easel is the better fit for readers who want a graphical workflow, machine profiles, material and tool settings, simulation, and broader design features. RasterCarve is more attractive when the priority is a free local command-line tool that can be scripted or integrated into an automated workflow. Easel’s claim of support for 148 validated CNC routers from 25 manufacturers is a vendor claim and should be treated as time-sensitive.
WinTopo and other raster-to-vector tools
WinTopo is relevant when the goal is to trace scanned drawings, logos, or line art into vector geometry. It is not a direct substitute for RasterCarve’s grayscale, depth-based engraving workflow.
Dedicated photo-carving software
The original Hackaday coverage compared RasterCarve with Vectric PhotoVCarve and described the commercial product as more feature-rich. Its article-era $149 price is from January 2020 and should not be treated as current pricing.
Who should use RasterCarve?
RasterCarve is a good fit if you:
- Want to engrave photographs, grayscale paintings, or tonal artwork.
- Are comfortable working from a command line.
- Understand CNC zeroing, tooling, feeds, speeds, and G-code safety.
- Want a free, open-source, scriptable tool.
- Can adapt the output to your controller and verify it before cutting.
It is a poor fit if you need polished GUI design, stock-aware simulation, collision checking, tabs, contour and pocket operations, 3D relief CAM, automatic photo cleanup, specialized post-processing, or actively maintained commercial support.
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Bottom line: RasterCarve remains a practical lightweight option for technically confident CNC users who want to turn bitmap brightness into a raster engraving toolpath without buying dedicated photo-carving software. Its age and limited scope matter: treat every generated file as unverified G-code, preview and air-cut it, match the tool geometry and controller requirements, and test on scrap before committing valuable material.
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