Image to laser engraving

How to make a laser engraving file from a photo

1. Open the photo. Tap Choose a photo, drop the file on the box, or paste a copied picture. A close crop of the subject engraves better than a wide scene; crop it first if needed.
2. Set the size and resolution. Type the engraving width in mm or inches (the height follows the photo) and either the DPI or the line interval your laser software uses. The pixel size of the file is shown underneath: 50 mm at 0.1 mm is 500 pixels.
3. Tune the tone. Pick the material as a starting point, then adjust: wood and leather burn darker than the photo, so lift the gamma; slate and dark anodised aluminium mark light, so invert.
4. Choose a dither. Look at the 1:1 preview, where one file pixel is one screen pixel, and drag the handle to compare with the photo.
5. Download PNG or BMP and import it into your laser software at 100 % size, with its image mode set to pass-through or threshold so it does not dither the dots again.

What it cannot do

• It does not drive a laser or write G-code. It makes the picture; your laser software turns it into moves.
• It does not suggest power or speed. They depend on the machine, the lens, the material and its finish; run a test grid on a scrap of the same material first.
• It makes raster files, not vector cut paths. For outlines to cut or score, use Image to SVG.
• It cannot add detail. A small or blurry photo stretched to 200 mm at 254 DPI gives soft dots; the stats line under the preview shows the photo's own resolution at your size.
• Files over 30 megapixels are refused (for example 300 × 300 mm at 0.05 mm, which is 36 megapixels), because a phone can run out of memory; use a coarser interval or a smaller size.
• Presets are starting points. Two pieces of the same wood can burn differently; they set sliders only.

Why the dots must match your line interval

A laser does not burn greys: at each point it fires or it does not. Dithering turns grey into a pattern of burnt and unburnt dots whose density matches the grey, so the eye sees a tone. That only works if every dot in the file lands on exactly one spot of the laser. If the file is 300 DPI and the laser engraves at 0.1 mm (254 DPI), the software has to resample the dots, and the careful pattern turns into blotches and stripes. So the file here is made at the same pixel grid as the engraving: width in mm ÷ line interval in mm = pixels. An 80 mm coaster at 0.1 mm is 800 × 800 pixels; at 0.08 mm (317.5 DPI) it is 1,000 × 1,000.

The PNG stores the resolution in its pHYs chunk as pixels per metre (254 DPI = 10,000 px/m, unit 1 = metre), and the BMP in biXPelsPerMeter and biYPelsPerMeter. Software that reads these opens the file at the right physical size; if yours ignores them, type the width you set here.

Error diffusion (Floyd–Steinberg, Jarvis, Stucki, Sierra, Atkinson) sets each pixel to black or white and pushes the rounding error onto the neighbours not yet visited, in fixed shares: Floyd–Steinberg gives 7/16 to the right and 3/16, 5/16 and 1/16 to the row below; Jarvis spreads it over 12 pixels in 48ths. Atkinson passes on only 6/8 of the error, so tones away from mid-grey drift outwards: a 25 % grey comes out with about 18 % of its dots burnt instead of 25 %, and the darkest shadows clip to solid. Bayer dithering compares each pixel with a fixed 4 × 4 or 8 × 8 grid of thresholds instead, so a 50 % grey gives a perfectly even checker pattern.

Questions

Is there a free online image to laser engraving converter?

Yes, this page. Open a photo, set the size of the engraving and your laser's line interval or DPI, and download a one-bit PNG or BMP. It is free with no sign-up and no watermark, and the photo is processed by your own browser, so it is never uploaded.

What file does my laser software need for a photo engraving?

A black-and-white (one-bit) raster at exactly the size and resolution you will engrave at. This page writes that: the PNG carries its DPI in the pHYs chunk and the BMP in its pixels-per-metre fields, so software that reads them imports it at the right physical size. In the laser software choose the pass-through or threshold image mode, not another dither, and set the line interval to the one you used here.

Which dithering method is best for laser engraving?

For portraits and photos, Jarvis–Judice–Ninke or Stucki: they spread the error over 12 neighbours and give smooth skin with little worm-like texture. Floyd–Steinberg is sharper but grainier. Atkinson gives crisp, high-contrast results and drops the deepest shadows to solid. Bayer gives a regular cross-hatch that burns evenly on materials that char unevenly. Halftone makes printed-newspaper dots that hold up on leather and slate.

What DPI or line interval should I use?

Use the line interval you set in your laser software, and keep it close to the laser's spot size. Most diode lasers have a spot of about 0.08 to 0.15 mm, so 0.1 mm (254 DPI) is a common start; on wood, which spreads each burn, 0.12 to 0.15 mm (212 to 169 DPI) often looks cleaner. DPI = 25.4 ÷ interval in mm.

Can I just dither an image online for something else?

Yes. Every method here makes a plain black-and-white picture, so the PNG works for thermal and receipt printers, e-ink screens, screen printing positives and the one-bit look in general. Set the size in pixels by choosing inches and a DPI, for example 4 inches at 100 DPI for 400 pixels.