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CSS Alpha Masking

Meng ToCommunityCreated by Meng To

  • Skill
  • Tool integration
  • Software development
  • MIT
  • No issues found
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From the author

Apply CSS alpha masking with linear-gradient for horizontal or vertical edge fades (mask-image and -webkit-mask-image). Use when asked for alpha masks, fade edges, or CSS mask gradients.
— the description by Meng To

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a standardized approach to implementing CSS alpha masking using linear-gradient properties. It ensures cross-browser compatibility by including both standard mask-image and vendor-prefixed -webkit-mask-image properties, allowing developers to create smooth horizontal or vertical fades for images, text, or containers.

What it does

  • Generates CSS snippets for horizontal and vertical edge fading.
  • Ensures Safari compatibility by providing the necessary vendor-prefixed properties.
  • Offers guidance on adjusting fade depth and intensity using percentage stops and alpha values.
  • Provides a structured workflow for gathering requirements like direction and fade width.

When to use it

  • When you need to fade the edges of an image or container into transparency.
  • When implementing UI effects that require smooth transitions at element boundaries.
  • When you need a quick, copy-pasteable CSS solution for alpha masking.
  • When you need to ensure your CSS masks work consistently across different browsers.

Advantages

  • Reduces manual CSS configuration time for common masking patterns.
  • Prevents common cross-browser issues by including required vendor prefixes.
  • Provides clear customization options for fine-tuning fade intensity and direction.
  • Standardizes the implementation of visual edge effects across a project.

Usage examples

“Create a horizontal fade for my image gallery container.”
The agent provides the CSS snippet using linear-gradient(to right, ...) with both standard and webkit properties to ensure the container fades out at both ends.
“How do I make a top-to-bottom fade that is very subtle?”
The agent provides the vertical mask CSS and suggests changing the transparent stop to a semi-transparent color like rgba(0,0,0,0.2) for a softer effect.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/mengto/css-alpha-masking/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip css-alpha-masking.zip -d .agents/skills

Documentation by Meng To

CSS Alpha Masking Skill

Workflow

  1. Confirm direction (horizontal or vertical) and fade stop percentages.

  2. Provide the inline CSS snippet and any needed class usage.

  3. Offer small tweaks only (direction, stop positions, colors).

Usage checklist

  • Apply the mask styles directly on the element or in a CSS class.

  • Always include both mask-image and -webkit-mask-image for Safari.

  • Ensure the element has visible content; masks reveal/hide alpha only.

Horizontal (left/right) fade

/* Add this inline CSS to any element */
mask-image: linear-gradient(to right, transparent, black 15%, black 85%, transparent);
-webkit-mask-image: linear-gradient(to right, transparent, black 15%, black 85%, transparent);

Vertical (top/bottom) fade

/* Add this inline CSS to any element */
mask-image: linear-gradient(to bottom, transparent, black 15%, black 85%, transparent);
-webkit-mask-image: linear-gradient(to bottom, transparent, black 15%, black 85%, transparent);

Customization knobs

  • Direction: to right, to left, to bottom, to top.

  • Fade depth: adjust 15% and 85% stops.

  • Strength: change transparent to rgba(0,0,0,0.2) for softer fades.

Common pitfalls

  • Forgetting the -webkit-mask-image fallback in Safari.

  • Expecting masks to work on elements with overflow: hidden but no visible content behind.

Questions to ask when specs are missing

  • Which direction should the fade go?

  • How wide should the fade edges be?

  • Is this for images, text, or a container background?

Files

ATTRIBUTION.md

Attribution

This folder is an unmodified copy of the Agent Skill "css-alpha-masking", distributed by AutoGineer (https://autogineer.com/agent-skills).

The skill's own files are unmodified copies. AutoGineer is not affiliated with or endorsed by the author or the publisher.

Files added by AutoGineer

  • ATTRIBUTION.md: this file, written by AutoGineer

  • LICENSE: copied from LICENSE

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by
Meng To
Publisher
Meng To (Community)
Source
MengTo/Skills · agent-skills/web-design/css-alpha-masking · commit 5ea1661
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced

AutoGineer is not affiliated with or endorsed by Meng To or Meng To.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download css-alpha-masking.zip