RasterCarve Converts Images to CNC: What It Does and How to Use It

RasterCarve is a small, open-source Python utility that converts bitmap images into raster-style G-code for CNC engraving. It is useful for turning grayscale photographs, artwork, and logos into depth-varying toolpaths, but it is not a CNC controller, a general-purpose CAM package, or a substitute for machine setup and safety checks.

The project remains available through PyPI. However, the latest release shown there is RasterCarve 1.0.8, uploaded on March 25, 2020, so its age and current maintenance status should be considered before relying on it for production work.

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What RasterCarve does

RasterCarve follows a straightforward image-to-toolpath workflow:

1. You provide a bitmap image.
2. The program reads the image using an OpenCV-supported format.
3. It samples the image along a series of raster lines.
4. Pixel intensity is mapped to cutting depth.
5. It writes G-code describing the resulting toolpath.
6. You load that G-code into a compatible CNC sender or controller.
7. The machine engraves the image line by line.

The normal mapping described by the project makes darker pixels produce deeper cuts. That means the finished result depends heavily on grayscale conversion, contrast, image inversion, tool geometry, material, and the maximum depth selected. Always preview and test the output rather than assuming the source image will reproduce exactly.

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RasterCarve is distributed as a Python package under the GPLv2-or-later license, and its package metadata identifies Franklin Wei as the author. The package description also references a hosted version at rastercarve.live, but its current uptime, maintenance, privacy policy, and security should be confirmed before use. Do not upload sensitive images without checking those terms.

Raster engraving is not vector cutting

RasterCarve is primarily a raster-image engraving tool. The cutter sweeps across the work in rows or angled passes, with image brightness controlling depth or a related engraving parameter.

That differs from vector machining, where the machine follows explicitly defined lines, curves, outlines, pockets, or profiles. RasterCarve does not automatically turn a photograph into clean SVG or DXF geometry.

Use a raster workflow for photographic or grayscale relief-style engraving. If you need to trace a logo, scanned drawing, or line-art design into editable outlines, a raster-to-vector tool such as WinTopo is a better match, followed by conventional CAD/CAM processing.

Installing RasterCarve

The published package metadata lists Python 3.6 or newer. That requirement comes from the 2020 release and does not prove that every modern Python version or operating-system combination has been tested.

A virtual environment keeps RasterCarve separate from other Python projects:

python -m venv .venv

Activate it in Windows PowerShell:

.venvScriptsActivate.ps1

Or on macOS and Linux:

source .venv/bin/activate

Install the package and check its local command-line interface:

python -m pip install rastercarve
rastercarve --version
rastercarve -h

If the rastercarve command is not found, check that the virtual environment is active and that its scripts directory is on your system path. Running rastercarve -h is important because the installed version’s help output is the best reference for option names and semantics.

Converting an image to G-code

The documented basic example is:

rastercarve --width 10 examples/test.png > out.nc

This requests an output image 10 inches wide and redirects RasterCarve’s G-code from standard output into out.nc. The shell operator > is not a RasterCarve option; it is normal command-line redirection.

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You can specify height instead:

rastercarve --height 8 photo.png > photo.nc

Exactly one of --width or --height must be supplied. RasterCarve calculates the other dimension from the image’s aspect ratio. Keep source images and generated files clearly separated, for example:

images/portrait.png
toolpaths/portrait-8in.nc

Important command-line options

The complete published usage information is available on the RasterCarve PyPI page.

Prepare the image before generating toolpaths

Image preparation often matters more than the conversion command. A photograph with poor contrast or excessive fine detail can produce a muddy, fragile, or impractically long carve.

1. Crop the composition. Remove empty areas and place the subject within the intended stock dimensions.
2. Convert to grayscale. Color information must ultimately be represented as a depth or intensity range.
3. Adjust contrast. Separate the subject from the background without creating harsh, unusable extremes.
4. Reduce noise. Small photographic artifacts can become unnecessary tool motion.
5. Resample sensibly. Match image detail to the cutter, stepover, and physical output size.
6. Check the light-to-dark relationship. Decide whether the desired result requires an inverted image.
7. Save a lossless working copy. PNG is a practical choice for preserving the prepared image.

A flat, low-contrast image may produce little visible variation. An aggressively sharpened image may create chatter, excessive detail, or fragile features. Preview the toolpath and make a small test cut before committing valuable stock.

What the published example reveals

The project documentation reports the following statistics for one example: a 512 × 512-pixel input, a 10 × 10-inch output, a maximum depth of 0.080 inch, a maximum line width of 0.043 inch using a 30-degree V-bit, 0.047-inch line spacing, a 22.5-degree line angle, 277 lines, 51.2 PPI input resolution, 100 PPI output resolution, and a 2,202.6-inch toolpath.

That example uses a 100-inch-per-minute feed rate and a 30-inch-per-minute plunge rate, with an estimated machining time of 1,351.2 seconds—about 22.5 minutes. These are published example statistics, not universal defaults or safe settings for every machine.

The important lesson is scale: a physically small image can still produce a very long toolpath. Output dimensions, stepover, line angle, point resolution, and image complexity all affect file size and machining time.

Preview and validate the G-code

A generated .nc file is not automatically safe. Before cutting, inspect it in a simulator or G-code previewer and verify:

• Units are correct.
• X and Y move in the expected directions.
• Positive Z moves clear the work and fixtures.
• The origin matches the intended workpiece corner.
• The maximum X and Y extents fit within machine travel.
• The maximum depth is suitable for the material.
• The feed, plunge, spindle, and controller commands are supported.
• The preamble and epilogue match the machine’s requirements.
• The first and last several lines are sensible.

The package documentation points to a standalone previewer at github.com/built1n/rastercarve-preview. Its current availability and maintenance status should be verified locally rather than assumed.

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For an unfamiliar controller, perform an air cut with the tool above the workpiece and the spindle disabled. Then test the path on scrap material. Keep an emergency stop accessible and do not leave the first run unattended.

Machine setup for a first carve

1. Install the correct tool. RasterCarve documentation prefers an engraving bit, although an ordinary V-bit may produce acceptable results.
2. Match the tool angle. The generated -t value should correspond to the actual cutter. The documentation cites 30 degrees as its default example, not as a universal requirement.
3. Secure the material. Use reliable workholding and confirm that clamps cannot enter the toolpath.
4. Zero X and Y. The documented procedure places the origin at the top-left corner of the intended image area.
5. Check travel. Confirm that the lower-right extent remains inside the machine’s usable travel.
6. Zero Z. Set Z to the material’s top surface using the procedure appropriate to your machine.
7. Load the validated file. Confirm units, origin, and controller settings one more time before starting.

Material behavior varies. The project documentation reports that MDF worked best in its testing, while plywood and ordinary lumber were more prone to chipping. It also reports that plastics could melt and stick to the bit. Treat those observations as project-specific guidance, not a complete feeds-and-speeds specification for every material.

G-code compatibility is controller-dependent

RasterCarve produces G-code, but that does not mean the file will run unchanged on every CNC machine. Compatibility depends on the controller dialect, units, coordinate conventions, positive-Z direction, supported motion and spindle commands, line-number requirements, and machine-specific preamble or epilogue.

ShopBot users should pay particular attention to the package warning about --no-line-numbers. Do not remove line numbers unless you have confirmed that your controller accepts the result.

If the controller rejects the file or behaves unexpectedly, inspect the generated text, run the installed help command, add the required machine-specific preamble, and test the revised file through simulation and an air cut. Generic G-code should never be assumed to be universally interchangeable.

Common problems and recovery steps

The physical size is wrong

Symptoms: The carving is stretched, compressed, or larger than the stock.

Likely causes: An incorrect --width or --height, wrong unit assumptions, or a mismatch between generated dimensions and controller coordinates.

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The image is inverted

Symptoms: The background is deep while the subject is shallow, or the reverse of the intended appearance.

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Fix: Invert the grayscale source before processing, preview the result, and test it on scrap. Do not judge final appearance from the photograph alone.

The job takes too long

Likely causes: Fine stepover, high image resolution, large output dimensions, or a long angled raster path.

Fix: Reduce image resolution after preserving necessary detail, simplify the image, reduce physical size, or increase stepover cautiously. Compare the generated statistics before machining.

Edges chip or fine detail becomes fuzzy

Likely causes: Grain direction, dull tooling, excessive depth, unsuitable stepover, or more image detail than the material can reproduce.

Fix: Test stable stock such as MDF, reduce maximum depth, use a sharper engraving tool, improve contrast, simplify the artwork, and secure the work firmly.

Plastic melts onto the cutter

Likely causes: Heat buildup, unsuitable feeds and speeds, or the properties of the particular plastic.

Fix: Test on scrap and tune feed, spindle speed, depth, and chip evacuation for that specific material and tool. The project warning is a starting point, not a complete plastics recipe.

The controller rejects the file

Likely causes: Unsupported G-code, missing preamble, wrong units, incompatible line numbering, or different coordinate conventions.

Fix: Inspect the file, confirm the controller dialect, add the required preamble or epilogue, preview it, and perform an air cut before enabling the spindle.

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How RasterCarve compares with alternatives

Easel

Easel is a broader browser-based CNC design and toolpath environment. Its official page showed, during a crawl approximately four weeks before August 18, 2026, a free plan at $0 per month, Easel Starter at $8 per month or $72 per year, and Easel Pro at $24 per month or $216 per year. These prices and plan limits are time-sensitive and should be checked again before purchase.

The same page advertises raster carving in Starter and broader 3D carving, V-carving, design-library, and machine features in Pro. It also claims support for 148 validated CNC routers from 25 manufacturers; that is a vendor claim and should be treated as date-specific.

Choose Easel when you want a graphical workflow, machine profiles, material and tool settings, simulation-oriented features, and broader CAM functions. Choose RasterCarve when you prefer a free local script, automation, and direct control over raster-toolpath generation.

WinTopo

WinTopo is relevant when the real goal is raster-to-vector conversion. Its official site describes converting raster images into vector data for CAD, GIS, and CNC applications. That suits logos, scanned drawings, and line art that need editable outlines. It is not the same workflow as producing grayscale depth engraving directly from a bitmap.

Dedicated photo-carving software

The original Hackaday coverage compared RasterCarve with Vectric PhotoVCarve and described the commercial product as more feature-rich. The $149 figure mentioned in that 2020 article is historical and should not be treated as a current price.

Dedicated software may be preferable when you need polished image controls, integrated previews, supported post-processors, or commercial assistance. Conventional CAD/CAM is a better choice for contours, pockets, tabs, profiles, collision-aware work, and 3D relief machining.

Who should use RasterCarve?

RasterCarve is a good fit if you:

• Want grayscale or photographic engraving rather than outline cutting.
• Are comfortable with a command-line workflow.
• Already understand CNC zeroing, tooling, workholding, feeds, and G-code safety.
• Want a free, open-source, scriptable option.
• Can configure the output for your controller.
• Are willing to tune depth, stepover, feed, and tool geometry.

It is a poor fit if you need a polished GUI, full stock and collision simulation, tabs, conventional pocketing, 3D relief CAM, automatic photo effects, active commercial support, or a clean SVG/DXF outline. It is also a poor choice for unattended experimentation on valuable stock.

Verdict

RasterCarve is a useful, focused utility for technically confident CNC users who want to turn bitmap intensity into raster engraving G-code without buying a dedicated package. Its strengths are simplicity, scriptability, and an open-source distribution. Its limitations are equally important: it is an older project, not a complete CAM environment, and its output still requires careful validation for the target machine.

Use it for controlled experiments and repeatable raster engraving, but prepare the image carefully, match the tool geometry, preview the G-code, perform an air cut, and test on scrap before running the real job.

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