Reliefs, silhouettes and lithophanes, sized in millimetres and checked in a slicer before the spool starts turning.
Convert an image to STLYou have a flat image: a logo, a silhouette, a scanned sketch. You want a physical part from it. The jump from pixels to a printable mesh is where most attempts fail. Pixels have no height, no wall thickness and no idea what a nozzle can do. An image to STL for 3D printing conversion is really a decision about depth: how tall each grey value or colour region becomes, and how that height turns into printable geometry.
The failure is rarely dramatic. The mesh looks fine in a viewer, then the slicer highlights open edges, or the model is 12 mm wide when you needed 120 mm, or every colour in the source collapses into one grey lump. STL stores triangles, not texture. If your image carried meaning through colour, that meaning has to be carried by height instead. Decide that before you convert, not after.
This page is written for the print, not the preview. It covers the three ways makers turn a raster image into a relief or a silhouette, how to give the result a real size in millimetres, and what to look at in a slicer before the spool starts turning. A basic conversion runs in the browser with no account. Nozzle diameter, layer height and orientation are your decisions, and they matter more than the conversion settings.
Pick the workflow by what the finished part has to do.
Greyscale brightness becomes Z height, so a 0 to 255 pixel range maps to a known depth. Good for logos, terrain tiles and coin dies. Keep the depth modest, around 0.6 mm to 1.5 mm, or fine detail turns into steep cliffs your nozzle cannot follow.
Threshold the image to a solid mask and extrude that shape to a fixed thickness. This suits signs, keyrings, stencils and cake toppers. A 3 mm to 6 mm extrusion on a 0.4 mm nozzle gives a part that survives being handled and posted.
Brightness controls panel thickness instead of height, so the image appears when light passes through. Print it standing, face outward, at 0.1 mm layers. A minimum thickness near 0.8 mm keeps the panel from splitting between perimeters.
Walk a two colour PNG through to a sliced file.
Crop away everything that is not the shape, and push the background to pure white or transparent. Raise the long edge to at least 1200 pixels, because the converter can only trace the edges it is given. Save as PNG or SVG and keep that original.
The tool accepts JPG, PNG, GIF, BMP, TIFF, WebP, SVG and HEIC, up to 20MB. Choose the mode that matches your workflow: relief, silhouette or lithophane, and set invert if the shape comes back inside out. The result downloads as an STL.
An STL has no unit, and most slicers read one unit as one millimetre. Import, measure across the widest feature with the slicer's ruler, and scale by the ratio you need. A part that should be 120 mm across but imports at 12 mm needs a scale factor of 1000 percent.
Look at the mesh in the slicer's repair or X-ray view for open edges, flipped triangles and separate shells. Thin features below about 0.8 mm will not survive a 0.4 mm nozzle, so thicken them in the source image and convert again rather than accepting a fragile wall.
Rotate the model so no surface overhangs past roughly 45 degrees from vertical, then enable supports only where the preview shows sagging. Step through the layer preview at the first layer, at any bridge, and at the top of the relief. Check the slicer's own time and filament estimate before you start.
Six checks that catch most failed prints before you load filament.
Upload a JPG, PNG, GIF, BMP, TIFF, WebP, SVG or HEIC up to 20MB and download an STL, ready to size and check in your slicer. A basic conversion is free, needs no account, and runs in the browser on Windows, macOS, Linux, iOS and Android.
Yes. A basic conversion runs in the browser, needs no account and produces a downloadable STL. The maximum upload is 20MB, and the accepted formats are JPG, PNG, GIF, BMP, TIFF, WebP, SVG and HEIC. Everything happens on the page, so there is nothing to install.
The pages that answer the next question after this one.
Skip the complex modeling software. Upload your image now and get a print-ready STL file instantly.
Start Converting Free