Original
+
Drop artwork here
or click to browse
or click to browse
PNG · JPG · PDF · WEBP · HEIC
Preview
Pages
single click = view · double click = select / deselect
0 / 0
Style
Regular
Export
ZIP — organize by:
Riso ink library
84 inks
stencil.wiki · with pairings
Select an ink to see details
Pairings based on colour theory and riso community practice. Overprint colours are approximations only.
Palettes
Paper library
— stocks
Select a paper to see details
Ink rendering on coloured stock is approximate. Always test-print on actual paper before full runs.
Documentation
About
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Workflow
From file to riso-ready export
Getting started
This app prepares color separations for risograph printing. Each ink color becomes a separate greyscale file, ready to send to your riso printer.
1
Open a file. Drag and drop or click the canvas to load a PNG, JPG, PDF, WEBP or HEIC file. Multi-page PDFs are supported — use the filmstrip to navigate and select pages for export.
2
Choose your inks. Go to the Inks tab and select the colours available at your print studio. These correspond to the physical ink drums on the machine.
3
Build a palette. In the Palettes tab, create a combination of 2–4 inks for your print job. Each ink will receive its own separation layer.
4
Adjust style and parameters. Choose a separation mode (Regular, Halftone, Dithering…) and tune LPI, DPI, levels and angle to match your printer's capabilities.
5
Preview and toggle layers. Click any ink layer to show or hide it in the preview. The right pane updates in real time. Both panes share the same zoom and pan position.
6
Export. Choose PNG, PDF or ZIP. Files are named by ink colour and ordered for printing. DPI metadata is embedded in each file.
Multi-page PDFs
Use the filmstrip at the bottom of the canvas to navigate pages. Single click to view a page. Double-click to select or deselect it for export. Selected pages have a green border; excluded pages appear faded with a dashed border. The current view is highlighted in orange.
Parameters
Separation modes and technical settings
Separation modes
Regular
Direct channel extraction. Best for vector artwork and illustrations with flat colours.
Start here if you're unsure.
CMYK-ish
Maps artwork through a CMYK approximation before separating. Works well for photographs and full-colour images.
Good for photos with natural tones.
Halftone
Converts each layer into a dot screen. Controls: LPI (dot frequency), angle, and DPI.
Classic riso look. Use 45–75 LPI.
Dithering
Error-diffusion or ordered dithering. Creates a pixelated, textured tone.
Floyd-Steinberg for smooth, Atkinson for graphic.
Posterize
Reduces the image to a fixed number of flat tone levels. Use the Levels slider to control posterisation.
2–4 levels give bold, graphic results.
Settings
LPI
Lines per inch — controls halftone dot size. Lower = coarser, more visible dots. Higher = finer screen.
Recommended: 45–85 for riso.
Angle
Screen angle per ink layer. Stagger angles between inks to minimise moiré patterns.
Classic: 45° (dark), 75°, 15°, 0° (light).
DPI
Export resolution. 300 dpi for standard print, 600–1200 for fine detail or large format.
300 dpi is sufficient for most riso work.
Levels
Number of tone levels in Posterize mode. Also affects step count in Dithering.
Try 3–5 for a balanced result.
Recommended halftone angles
These angles are inherited from CMYK offset printing and work well for riso. Assign the darkest ink to 45°, as it carries the most visual weight. Lighter inks take 0° or 90° where moiré is less visible.
The app assigns angles in ink layer order, not by colour. Place your darkest ink first in the palette to get the 45° angle automatically.
Limitations
Known constraints and workarounds
Browser-based constraints
PSD export
PSD files with spot colour channels cannot be generated in the browser. Export as PNG layers instead, then assemble in Photoshop using the spot colour channel workflow.
Large files
Processing very large files (above ~50 MB or very high resolution) may be slow or cause the browser tab to run out of memory. Consider downscaling before importing.
ICC profiles
ICC colour profile workflows (as used in Spectrolite or color/shift) are not currently supported. Colour mapping is based on the 80 official Riso ink values.
Riso-specific notes
Keep ink coverage below 85% on large solid areas to avoid machine jams and tide marks. Riso cannot print at 100% density across the full sheet.
For full-bleed prints, add 4 mm bleed to all sides in your original file. The riso cannot print edge to edge.
Expect 2–3 mm of natural misregistration between ink passes. This is part of the riso aesthetic — design with it in mind rather than against it.
Compared to Spectrolite
For Mac users, Spectrolite remains the reference tool.
This app was built to address one specific constraint: Spectrolite is Mac-only. If you work on Mac, use Spectrolite — it supports ICC profiles, is faster for large files, and is maintained by its authors. This tool runs in any browser, on any OS, with no installation required.
This app is an independent open-source reimplementation. It is not affiliated with or endorsed by the Spectrolite team.
About
Open source · Independent · Free
This tool was built by an artist working in bookbinding, print and workshop-based practice. It exists because many studios, schools and residencies do not have access to Mac workstations — and colour separation for riso printing should not require one.
The project is open source. You are free to use it, fork it and contribute to it. No account, no tracking, no ads.
Spectrolite, the Mac app by Amelia and Adam Greenhall (ANEMONE), is the direct inspiration for this project. If you use a Mac, please use Spectrolite and support their work.
Source available on GitHub · holysheet.be/spectrolike