Brand and product teams need repeatable PNG previews for every theme when tokens change. This tutorial lists steps for OpenClaw on a remote Mac: Gateway, watch or scheduled tasks, token JSON batch renders, pixel-threshold comparison, and a diff report. You get a trigger matrix, pre-flight checklist, common errors with retries, and a CTA to MacPng blog, home, and help.
Table of Contents
Pain Points for Multi-Theme Brand PNGs
MacPng users ship logos, campaign art, and UI strips that must look correct in light, dark, and seasonal themes. Without automation, three problems appear:
- Silent drift: A hex tweak in tokens does not show up in every preview file, so marketing approves the wrong frame.
- Non-repeatable exports: Different machines use different font smoothing or color profiles, so PNGs never match CI.
- Weak review: Side-by-side folders are hard to scan; stakeholders need a threshold-based diff and a one-page summary.
OpenClaw ties skills and file access into one layer on macOS. Pair it with our OpenClaw install guide and a dedicated remote Mac so renders and Gateway probes always run in the same environment.
Trigger Matrix: Watch vs Schedule vs Manual
Pick how OpenClaw wakes your render skill. Use this matrix to decide.
| Trigger | Best for | Trade-off |
|---|---|---|
| Debounced folder watch | Designers drop updated tokens.json or exported SVG into inbox/ |
Needs stable Full Disk Access paths; avoid firing on every autosave |
Cron or launchd |
Nightly regression against main branch tokens | May process unchanged files unless you gate on git hash |
| Manual skill invoke | Before a release tag or stakeholder review | Depends on someone running the command over SSH |
For watch-folder patterns that scale to many PNG sets, reuse ideas from OpenClaw watch folders for PNG sets: coalesce events, write a processing lock file, and log each batch id.
Reproducible Pipeline Steps
- Prepare the remote Mac. Rent a Mac mini M4 node, connect with SSH or VNC using MacPng help, create project folders
tokens/,templates/,out/previews/,out/diff/,logs/. - Install OpenClaw and enable Gateway. Follow version pins from the install guide. Confirm the Gateway health URL returns OK and that your API key can read the project root.
- Register a skill or script. The skill should accept a theme list, render width and height, PNG naming rules, and paths to baseline PNGs for comparison.
- Wire triggers. Either watch
tokens/with a debounce of a few seconds or call the skill from CI after merge. - Render loop. For each theme, merge token values into your template, rasterize at a fixed device scale, and write
{component}_{theme}_{WxH}.png. - Compare and summarize. Diff each new PNG against the previous approved baseline using a pixel metric; save heatmaps only when the threshold fails.
- Publish artifacts. Write
report.mdorsummary.jsonunderout/diff/, upload to your DAM, or attach to a ticket.
Token JSON Contract and Render Loop
Keep one manifest per brand line. A minimal shape is: themes[] with id, colors map, radius, optional font tokens, and template path. Your OpenClaw step validates JSON schema before any headless render starts.
- Determinism: Fix DPR, disable animation, set background explicitly, embed sRGB ICC when your pipeline requires it.
- Naming: Use lowercase slugs so outputs sort predictably in Finder and in reports.
- Batch size: Render twelve to forty-eight previews per run on M4 before parallelizing; tune after measuring GPU and memory.
Threshold Comparison and Report Output
Use ImageMagick compare or an equivalent to produce a numeric score plus an optional heatmap PNG. Typical gates: changed-pixel percentage under one percent and RMSE under a calibrated ceiling on a 1024 px wide canvas.
Each report row should list theme, file, metric values, pass or fail, path to heatmap, and baseline hash. For broader PNG QA patterns, align checks with OpenClaw PNG QA batch checks so size, alpha, and palette rules live in one place.
Common Errors, Retries, and Logs
| Symptom | Likely cause | Retry pattern |
|---|---|---|
| Gateway 502 or timeout | Skill boot cold start or port conflict | Exponential backoff 2s, 4s, 8s; restart Gateway if three fails |
| Permission denied on write | macOS sandbox or wrong user over SSH | Align owner with whoami, fix ACLs, re-run once |
| Render blank or wrong colors | Missing font or P3 vs sRGB mismatch | Install fonts on the remote Mac, embed profile, re-render |
| Diff always fails | Anti-alias noise or size mismatch | Normalize size, fuzz slightly, or raise threshold after baseline review |
Append JSONL lines to logs/runs.jsonl with timestamp, git sha, pass count, and fail count so you can trace regressions.
Pre-Flight Checklist
- Gateway health OK; OpenClaw version pinned
- Token schema validated; template paths exist
- Output and log directories writable by the SSH user
- Baselines versioned; threshold numbers documented in README
- Watch debounce configured; lock file prevents overlapping runs
- Report uploaded or linked from your ticket system
FAQ
What belongs in a design token JSON for PNG previews?
Theme id, semantic colors, radii, and typography keys your template consumes. Use relative paths from the project root on the remote Mac.
Which diff threshold should we use?
Start near 0.5 to 1.0 percent changed pixels after normalization, then tune with known-good pairs from your brand system.
Why remote Mac for this pipeline?
Consistent macOS rendering, native design fonts, and isolation from your laptop. OpenClaw and batch PNG work match what creative teams already expect on Mac hardware.
Run OpenClaw Token Previews on a Remote Mac M4
Open MacPng home, the Tech Insights blog, and help for SSH and VNC; compare pricing for nodes.