# Cmyk Proof > ICC-accurate CMYK proofing for print work designed in screen-native canvas tools (Paper, Figma, or any hex-only design surface). Converts brand hexes to press recipes plus print-simulated canvas hexes, soft-proofs whole exports, derives ink tints, and flags out-of-gamut colors and total-ink violations via a bundled ImageMagick script. Use when designing anything physically printed (brochures, posters, packaging, stationery) in a tool without CMYK support, or when the user mentions CMYK, print-ready, gamut, ICC, press profiles, or colors that must survive printing. - Skill: `tommylower/cmyk-proof` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds@latest add tommylower/cmyk-proof` - Raw SKILL.md: https://api.skillmd.com/api/skills/tommylower/cmyk-proof/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Design & Media - Author: tommylower (https://skillmd.com/u/tommylower) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tommylower/cmyk-proof --- # CMYK Proof Screen design tools speak sRGB hex. Presses speak CMYK ink under a specific ICC profile. Saturated screen colors (neon reds, electric blues, vivid greens) silently desaturate at print time, and a naive hex-to-CMYK formula conversion tells you nothing about it. This skill closes the gap: every color is proofed through a real press profile before it touches the canvas, so what the client approves on screen is what the press can actually make. ## Requirements - ImageMagick 7 (`magick` on PATH). - A press ICC profile. Free and redistributable: [PSOcoated_v3 or ISOcoated_v2 from eci.org](https://www.eci.org/en/downloads) (European standard). GRACoL2013_CRPC6 ships with Adobe apps (US standard, common digital-press target). Ask the print vendor which profile they proof against; when in doubt, coated defaults above are right for most commercial work. - The script auto-detects installed profiles, or takes `--profile ` / the `CMYK_PROFILE` env var. ## Quick start ```bash # brand hex -> press recipe + the hex to actually use on canvas node scripts/cmyk_proof.mjs hex '#FF003D' '#2F6F95' # #FF003D -> C0 M96.2 Y74 K0 -> canvas #E72038 (out of gamut, drift 32) # #2F6F95 -> C79.2 M38.5 Y13.5 K19.1 -> canvas #2E6F95 (safe, drift 1) # recipe (percent) -> canvas hex, for colors born in ink node scripts/cmyk_proof.mjs cmyk '0,96,74,0' # tints of a recipe, without minting new colors node scripts/cmyk_proof.mjs tint '20,70,0,15' 15 20 40 # soft-proof a whole exported board node scripts/cmyk_proof.mjs image export.png proof.png ``` Verdicts: `safe` (drift ≤ 8/255 per channel), `shifts` (≤ 24), `out of gamut` (> 24). Every row also reports TAC (total area coverage, the four ink percentages summed); the script warns above 300%, a common coated-stock limit. Confirm the vendor's actual limit. `--json` for machine-readable output, `--intent` and `--tac` to override defaults. ## The born-CMYK workflow The law: **only print-simulated hexes enter the canvas, and production files are rebuilt from recipes, never converted from canvas hexes.** 1. Every candidate color goes through the script before use. Canvas gets the `canvas` hex from the output, not the original. 2. Record the recipe with the color wherever the tool allows: token descriptions, style notes, a palette board. Each color is dual-value, recipe for the press, sim hex for the screen. When print files are built (InDesign, Affinity, or direct to the vendor), colors are re-entered from the recorded recipes. 3. If a brand color is out of gamut, do not quietly use it. Show the owner the original next to the print simulation, offer in-gamut candidates, and get an explicit pick. If the unprintable original must stay in the file as a reference, keep it raw and visibly labeled not printable, never as a reusable token. 4. Tints come from the `tint` mode (scaled ink recipes), not from screen opacity. A 20% opacity overlay and a 20% ink tint are different colors. 5. Judge candidates in context: proof swatches sitting on the background color they will print over, never isolated on white. ## Ink discipline - Body text and fine rules: single-ink black (`cmyk '0,0,0,100'`, or a K-only tint for grays). Four-ink builds on small type risk registration fringing and color casts. - Large dark solids: rich black, e.g. `cmyk '60,40,40,100'` (confirm the vendor's preferred build). A hex near-black converted from screen becomes an accidental four-ink build, the TAC warning will usually catch it. - Grays: K-only tints via `tint '0,0,0,100' `, not CMY mixes. - Avoid reversing small type out of multi-ink builds for the same registration reason. ## Canvas hygiene - If the tool supports variables or tokens, bind every swatch and fill to them. After copying nodes between files, verify the bindings survived, copies often flatten to raw hex. Re-check by reading values back, not by eye. - The canvas is the spec, not the print artwork. Exports are for approval and mockups; final artwork is rebuilt in a print-capable tool from the recorded recipes and the geometry spec. - Before client review of near-final boards, run the full export through `image` mode and look at the proof, not the raw export. ## Physical geometry Pixel-native tools also lack print units, bleed, and fold handling. See [references/print-geometry.md](references/print-geometry.md) for the ppi math, bleed/trim/safe setup, and fold-allowance rules.