Pixel Sprite Outline — real-time outline effect

Sprite Outline adds a crisp, pixel-perfect outline to any SpriteRenderer using just a single component. Designed specifically for pixel art and 2D sprites, it respects hard pixel edges and delivers clean outlines at any resolution.

No material editing. No shader graphs. No post-processing.
Just go to Add Component > Effects > Sprite Outline, and it works instantly on any sprite!

✨ Features

• Zero Setup: Attach the component, and the outline appears immediately.
• Pixel-Perfect Edge Detection: Works beautifully with pixel art sprites.
• Adjustable Thickness: Fine-tune outline thickness from 0 to 16 pixels.
• Full Color Control: Pick any outline color via the Inspector or runtime API.
• Alpha Threshold: Adjust which sprite edges get outlined (great for anti-aliased sprites).
• Sorting Offset: Renders cleanly behind the sprite with zero z-fighting.
• Animation-Ready: Fully compatible with Unity Animator, sprite swapping, and flipping.
• Pipeline Agnostic: Seamlessly supports Built-in, URP, and HDRP.
• Runtime API: Control SetOutlineColor, outlinePixels, and more directly from your code.

⚙️ How it works
The component creates a lightweight overlay mesh behind your sprite and uses an edge-detection shader that samples 8 neighboring pixels. Only the edges are colored—the original sprite remains completely untouched. The result is a clean outline that flawlessly follows your sprite through animations, scaling, rotation, and flipping.

🚀 Performance

• Highly Optimized: Only 1 extra draw call per outlined sprite.
• Lightweight: Just 4 vertices per outline mesh.
• No Overhead: Zero render textures, command buffers, or post-processing passes required.

🎨 Customization (Inspector Properties)

• Outline Color: Choose any color.
• Outline Pixels: Set thickness (0 to 16).
• Alpha Threshold: Define which alpha values count as an edge (0.0 to 1.0).
• Sorting Order Offset: Adjust the render position relative to the base sprite.

🎯 Suitable for

• Pixel Art Games: Platformers, RPGs, and action games.
• Highlighting Elements: Interactable objects, enemies, items, or selected units.
• Visual Feedback: Hover effects, selection outlines, and targeting indicators.
• Any 2D Project: A versatile effect that works with any sprite texture.

📦 What's included

• SpriteOutlineRenderer.cs (Main component)
• SpriteOutlineOnly.shader (Edge-detection shader)
• Interactive demo scene with UI controls
• Demo character sprites (CC-0 licensed)
• Comprehensive documentation (PDF, HTML, and Markdown)

📌 Requirements

• Unity 2022.3 or later
• Compatible with Built-in, URP, and HDRP
• No additional packages required!