A native macOS app (or browser-based app) for halftone image processing and spot color separation aimed at artists who screen print. Drop in an image, choose a pattern, adjust settings, and export print-ready files and color proofs. Halftones allows you to experiment with many different options, mixing and matching color separation layers and halftones in different ways.
There are three modes:
- Grayscale / halftone, with a single halftone pattern.
- Color separation (which can include halftoned layers or a halftoned key plate)
- CMYK.
Built with Claude for my own purposes, but perhaps it's useful to you as well.
13 patterns: dot, euclidean dot, ellipse, diamond, hexagonal, line, crosshatch, concentric, brick, radial dots, radial lines, stochastic (FM dither), and Poisson-disk stipple.
- Grayscale — single halftone layer with ink/paper color preview
- CMYK — four-channel process separation with per-channel angle/LPI and composite preview
- Spot Color — LAB k-means palette extraction, per-color flat or halftone rendering, click-to-seed palette colors from the image, per-color and global trap, and a key plate (halftone of the full image overprinted on top of all color layers for tonal depth — with min/max dot, optional edge stroke, silhouette outline, a toggle to use the strokes without the halftone dots, a merge with darkest color option to fold the key into the darkest separation plate as one screen, and per-color knockout to keep the key's dots and/or stroke off specific inks so a flat color prints clean)
- Separation mode — knockout (default: exclusive regions, one ink per pixel) or build-up (nested cumulative overprint — each tone inks its plate plus every lighter plate beneath it; registration-forgiving, suited to tonal/duotone palettes). Build-up honors each layer's flat/halftone choice, and an optional overprint reach limits how far a lighter plate extends under darker ink — full misregistration protection at boundaries without flooding ink under the whole design
- Underbase — an optional base plate (union of all inked area, choked inward) printed first, e.g. white or silver under the full design
- Substrate color — set the paper/garment color the proof and preview composite onto, for previewing ink on colored stock
- Vectorize flat edges — optionally trace flat color plates into smooth vector outlines so diagonal/curved color boundaries aren't pixelated (staircased). A global default with a per-color override (e.g. smooth the flat masses but leave a fine line/hatch plate crisp) and a Rounding amount; applies to flat plates only. Curves are re-curved through an interpolating spline so circles render round even when the trace reduced them to facets — while genuine corners stay sharp, so angular art keeps its edges with no rounding needed
- Despeckle — jointly cleans up the color separation so adjacent layers never erode apart and leave paper showing through; low values remove stray specks, higher values smooth jagged boundaries
- Treat white as paper — reserve near-white as bare paper so every extracted color is a real ink (no wasted white plate) and white areas knock out to paper; turn off for white ink on colored stock
- Background layer — for transparent/cutout images, add a color plate covering exactly the transparent area, rendered flat or halftoned, with an adjustable bleed (as a percentage of the margin) that extends it out toward the trim edge (clipped at the trim so it never covers the crop marks)
- Merge plates onto one screen — every color (and the key plate) can pick the layer it merges into, folding same-ink layers (e.g. a black background + black layer + key) onto one screen instead of separate overprints. Choose a specific layer or Last printed color; chains resolve (A→B→C lands both on C), and a warning flags a target that isn't printed last, since anything printed after it covers the merged ink
- Layer order — drag layers by the grip to set the print order; a merged plate prints at its target's position, so ordering and merging work together
- Layer edit — brush paint/erase directly on a plate to fix a rough edge or drop a stray feature. The edited layer is isolated black-on-white while you work, with a ring cursor showing the exact brush footprint. Strokes edit ownership, not rendered pixels, so they survive later LPI/angle/threshold/trap changes and flow through to underbase, key knockout and merges. The key plate gets an erase-only brush that clears dots, stroke and outline together. Saved per layer in the project file
- Palette library — save the current inks as a reusable palette and apply it later to recolor your layers in one click (separation untouched). Picked by swatch preview, names optional; palettes carry the background ink too. Stored in app prefs, so they're reusable across prints
- Min/max dot, dot gain compensation, dot size multiplier
- Gamma — power curve over the full tonal range
- Shadows / Highlights — independent piecewise boost for each half of the tonal range
- Invert (swap ink/paper)
Crop, rotation, levels (black/white point + midtone gamma), plus pre-processing — blur (smooth gradients / suppress source noise), sharpen (unsharp mask with adjustable radius, so detail holds through the screen), and noise (film grain to break up banding). All applied before halftoning.
Load a mask that clips every plate at once — confine the artwork to a shape, knock out a region, etc.
- SVG (preferred — resolution-independent, stays crisp at any output DPI) or raster (PNG/JPG/WebP); always stretched to the image rect
- white = keep, black = cut, with automatic use of the image's alpha when present, an Invert toggle, and Auto/Alpha/Luminance source modes
- Stroke — a keyline tracing the mask boundary in your choice of width/color, exported as its own dedicated plate in spot mode
- Applies in the live preview and every export, and is non-destructive — the full source image is kept for palette extraction
- PNG — full-resolution with embedded DPI metadata, laid out on the full print page (margin, crop marks, alignment marks) like the other plate exports
- Channel PNGs — one black-on-white plate per channel (CMYK or spot), including key plate, laid out on the full print page (margin, crop marks, alignment marks) just like the PDF
- PDF — multi-page with crop marks, optional margin, optional alignment marks (crosshair + circle at each side midpoint for multi-layer registration)
- Spot plates are labelled by layer number (One, Two, Three…), staggered across the page so the labels don't overlap when plates are stacked for registration, and clear of the alignment marks
- Color Proof — WYSIWYG composite of all layers in their actual ink colors
- Vector PDF paths for dot, hex, ellipse, diamond, line, euclidean, and radial-line patterns
A live sidebar readout that turns the current job into a screen-room plan, using your shop's screen inventory:
- How many screens (= plate count), which frame size (smallest that fits the full output page and stocks a fine-enough mesh), and a suggested mesh per plate (halftone ≈ 4.5× LPI, flat ~230, white underbase = lowest/heaviest)
- Min Dot vs mesh warning when a halftone's highlight dot is too fine to hold on the suggested mesh
- Gang 2 plates per screen — pairs plates so consecutive print colors land on different screens (1&3 on one, 2&4 on another), halving the screen count with a wash-and-dry rest between runs
- Editable shop profile — your frame sizes, the mesh counts each comes in, and edge clearance; stored in app prefs
.halftonesproject files — a zip of the settings + source image, with named projects and auto-save- Replace Image… (File menu) — swap the source image while keeping every setting (colors, key plate, transforms, output size, margins, mask), so a finished separation setup can be reused on new art
- Finder previews — saved projects embed a thumbnail of the processed print and set it as the file's Finder icon (no QuickLook extension), and the Open Recent menu shows each project's thumbnail
- macOS Share Sheet: registered as an image opener — share directly from Photos ("Share Subject" etc.) or Finder → Open With → Halftones
- Margins — a single linked margin, or independent Top/Bottom and Sides values; crop marks and alignment marks live in the waste strip (removed on trim)
- Pan/zoom viewport with Fit and 100% (output-accurate) presets
- Transparent PNG source: transparent areas produce no ink on any plate
Download for macOS (Apple Silicon) — unsigned app; on first launch right-click → Open, or go to System Settings → Privacy & Security → Open Anyway. If macOS reports the app is "damaged" instead of giving that option, the quarantine flag set by your browser is the cause — clear it with xattr -cr /Applications/Halftones.app in Terminal, then open normally.
npm install
npm run dev # browser dev server at localhost:5173
npm run tauri:dev # native macOS windowDrop an image onto the canvas or use the file picker.
npm run build # typecheck + Vite bundle
npm run tauri:build # Halftones.app + .dmg → src-tauri/target/release/bundle/React 18 + TypeScript + Vite + Tauri 2. No backend. Rendering is canvas/WebGL2 (GPU fast path for common patterns with CPU fallback) + jsPDF for PDF export. Path2D batching and grayscale pre-computation keep the preview loop fast.
Currently built and tested on macOS only. Tauri 2 supports Windows and Linux and the codebase has no meaningful platform-specific code, so builds for other targets should be straightforward — mainly a matter of adjusting the bundle targets in tauri.conf.json and restructuring the app menu.
MIT