Weixin Long Image

Turn Weixin/Wechat replies into readable image cards by rendering HTML into long PNG screenshots. Use when a Weixin direct-chat reply would exceed 150 Chinese characters, when the user asks for a card, a beautiful visual, or a poster-like output, or when the content benefits from HTML-based rendering such as charts, tables, curves, timelines, relation diagrams, comparison layouts, dashboards, or mixed text-image presentation. First write HTML, then render it into an image.

Use this skill to turn rich HTML layouts into long PNGs for Weixin delivery.

Core Rule

In Weixin direct chats, if the reply body for the user would exceed 150 Chinese characters, treat this as a hard rule: prefer this skill over a long plain-text message.

When To Use

Use this skill when any of these is true:

• The Weixin reply would be long and hard to read as plain chat text.
• The user asks for a card, poster, beautiful layout, or visually polished output.
• The content needs HTML rendering power, such as:
  • charts
  • tables
  • timelines
  • curves / trend visuals
  • relation diagrams
  • dashboards
  • mixed text + image layouts
• You want stable final presentation rather than chat-native formatting.

Default Visual Standard

Unless the user explicitly wants a poster/card/dashboard style, default to a WeChat public-article layout, not a centered floating card.

Night Rule

In Asia/Shanghai time, if the image is being prepared at 22:00 or later, default to a dark-mode article template to reduce eye strain, unless the user explicitly asks for a light theme.

Default article layout

• Use a plain white page background.
• Keep only moderate side margins for readability.
• Do not wrap the whole article in a large rounded card with heavy shadow.
• Prefer continuous reading flow, like a WeChat public account article.
• Use readable typography, generous line height, and responsive images.

Default dark article layout after 22:00

• Use a dark page background with softened contrast.
• Keep the same article flow and margins as the daytime template.
• Avoid excessive glow, neon accents, or dashboard-style visuals unless explicitly requested.
• Preserve readability first: muted metadata, bright headings, comfortable code blocks, and responsive images.

Use card style only when appropriate

Reserve card/poster/dashboard styling for cases like:

• cover cards
• poster-like announcements
• KPI / dashboard views
• side-by-side comparison blocks
• highly visual share cards

For ordinary long articles, analysis notes, translated writeups, and image-heavy explanations, prefer article layout.

Reusable Templates

Use assets/wechat-article-template.html as the default starting point for daytime article-style pages. Use assets/wechat-article-template-dark.html as the default starting point for article-style pages prepared at or after 22:00 Asia/Shanghai.

They provide:

• WeChat-like article spacing
• narrower side margins
• no outer card shell
• responsive images
• readable tables
• wrapped code blocks
• simple note/tip blocks
• matched light/dark article styles

Workflow

1. Write a complete HTML document first.
2. For article-like content, choose the template by time:
   • before 22:00 Asia/Shanghai → assets/wechat-article-template.html
   • at or after 22:00 Asia/Shanghai → assets/wechat-article-template-dark.html
3. Render the HTML with scripts/render_long_image.py.
4. Send the PNG with the message tool using an absolute local path.
5. After the message send succeeds, immediately delete temporary render artifacts (.png and temporary .html) unless the user explicitly asked to keep them.
6. In Weixin direct chats, use message for any progress update; do not rely on multi-part assistant text arriving in order.

Quick Start

bash

python3 scripts/render_long_image.py \
  --input /absolute/path/to/page.html \
  --png-out /absolute/path/to/output.png

You may also pass raw HTML via --input or stdin.

Input Rules

• The script accepts complete HTML only.
• --input can be a file path or inline HTML.
• If --input is omitted, read HTML from stdin.
• --html-out is optional.
  • If provided, persist the rendered HTML there.
  • If omitted and --input is an existing HTML file, reuse that file.
  • If omitted and the source is inline HTML or stdin, create a temporary HTML file and auto-delete it after rendering.
• If the source content starts as text, convert it into HTML first.

Rendering Guidance

• Build for phone reading first.
• For long-form articles, prefer article layout over card layout.
• For tables, charts, diagrams, and mixed media, define layout explicitly in CSS instead of relying on browser defaults.
• If images are embedded in the HTML, make them responsive with max-width: 100% unless overflow is intentional.
• Use absolute output paths so the PNG can be delivered reliably.
• If the content is sensitive, write outputs inside the workspace or /tmp, send the PNG, then remove temporary files if appropriate.

Sending

Use message with the generated PNG path.

• action=send
• channel=openclaw-weixin
• media=/absolute/path/to/output.png
• message=一句很短的说明

Post-send cleanup

For temporary outputs, once message reports success, delete the local render artifacts immediately.

Typical cleanup:

bash

rm -f /absolute/path/to/output.png /absolute/path/to/output.html

Rules:

• Prefer writing temporary outputs under /tmp.
• Delete the PNG after a successful send unless the user asked to keep the file.
• Delete the HTML too when it is only an intermediate artifact.
• If render_long_image.py used inline HTML or stdin without --html-out, the script already auto-deletes its temporary HTML file; you still need to delete the PNG after send.

After a user-visible message send, reply with NO_REPLY to avoid duplicates.

Troubleshooting

• If Playwright cannot launch Chromium, verify the local Playwright browser runtime is installed.
• If the screenshot looks clipped, increase --width or fix the HTML/CSS layout first.
• If the result is too tall, split the content into multiple HTML pages and render multiple images.
• If the content is short and visually simple, skip this skill and reply normally.

Assets

• assets/wechat-article-template.html: Default daytime HTML template for WeChat-article-style long images.
• assets/wechat-article-template-dark.html: Default night-mode HTML template for WeChat-article-style long images after 22:00 Asia/Shanghai.

Script

• scripts/render_long_image.py: Render complete HTML into a long PNG screenshot.