Slack GIF Creator

---
name: slack-gif-creator
description: Knowledge and utilities for creating animated GIFs optimized for Slack. Provides constraints, validation tools, and animation concepts. Use when users request animated GIFs for Slack like "make me a GIF of X doing Y for Slack."
license: Complete terms in LICENSE.txt
---

# Slack GIF Creator

A toolkit providing utilities and knowledge for creating animated GIFs optimized for Slack.

## Slack Requirements

**Dimensions:**
- Emoji GIFs: 128x128 (recommended)
- Message GIFs: 480x480

**Parameters:**
- FPS: 10-30 (lower is smaller file size)
- Colors: 48-128 (fewer = smaller file size)
- Duration: Keep under 3 seconds for emoji GIFs

## Core Workflow

```python
from core.gif_builder import GIFBuilder
from PIL import Image, ImageDraw

# 1. Create builder
builder = GIFBuilder(width=128, height=128, fps=10)

# 2. Generate frames
for i in range(12):
    frame = Image.new('RGB', (128, 128), (240, 248, 255))
    draw = ImageDraw.Draw(frame)

    # Draw your animation using PIL primitives
    # (circles, polygons, lines, etc.)

    builder.add_frame(frame)

# 3. Save with optimization
builder.save('output.gif', num_colors=48, optimize_for_emoji=True)
```

## Drawing Graphics

### Working with User-Uploaded Images
If a user uploads an image, consider whether they want to:
- **Use it directly** (e.g., "animate this", "split this into frames")
- **Use it as inspiration** (e.g., "make something like this")

Load and work with images using PIL:
```python
from PIL import Image

uploaded = Image.open('file.png')
# Use directly, or just as reference for colors/style
```

### Drawing from Scratch
When drawing graphics from scratch, use PIL ImageDraw primitives:

```python
from PIL import ImageDraw

draw = ImageDraw.Draw(frame)

# Circles/ovals
draw.ellipse([x1, y1, x2, y2], fill=(r, g, b), outline=(r, g, b), width=3)

# Stars, triangles, any polygon
points = [(x1, y1), (x2, y2), (x3, y3), ...]
draw.polygon(points, fill=(r, g, b), outline=(r, g, b), width=3)

# Lines
draw.line([(x1, y1), (x2, y2)], fill=(r, g, b), width=5)

# Rectangles
draw.rectangle([x1, y1, x2, y2], fill=(r, g, b), outline=(r, g, b), width=3)
```

**Don't use:** Emoji fonts (unreliable across platforms) or assume pre-packaged graphics exist in this skill.

### Making Graphics Look Good

Graphics should look polished and creative, not basic. Here's how:

**Use thicker lines** - Always set `width=2` or higher for outlines and lines. Thin lines (width=1) look choppy and amateurish.

**Add visual depth**:
- Use gradients for backgrounds (`create_gradient_background`)
- Layer multiple shapes for complexity (e.g., a star with a smaller star inside)

**Make shapes more interesting**:
- Don't just draw a plain circle - add highlights, rings, or patterns
- Stars can have glows (draw larger, semi-transparent versions behind)
- Combine multiple shapes (stars + sparkles, circles + rings)

**Pay attention to colors**:
- Use vibrant, complementary colors
- Add contrast (dark outlines on light shapes, light outlines on dark shapes)
- Consider the overall composition

**For complex shapes** (hearts, snowflakes, etc.):
- Use combinations of polygons and ellipses
- Calculate points carefully for symmetry
- Add details (a heart can have a highlight curve, snowflakes have intricate branches)

Be creative and detailed! A good Slack GIF should look polished, not like placeholder graphics.

## Available Utilities

### GIFBuilder (`core.gif_builder`)
Assembles frames and optimizes for Slack:
```python
builder = GIFBuilder(width=128, height=128, fps=10)
builder.add_frame(frame)  # Add PIL Image
builder.add_frames(frames)  # Add list of frames
builder.save('out.gif', num_colors=48, optimize_for_emoji=True, remove_duplicates=True)
```

### Validators (`core.validators`)
Check if GIF meets Slack requirements:
```python
from core.validators import validate_gif, is_slack_ready

# Detailed validation
passes, info = validate_gif('my.gif', is_emoji=True, verbose=True)

# Quick check
if is_slack_ready('my.gif'):
    print("Ready!")
```

### Easing Functions (`core.easing`)
Smooth motion instead of linear:
```python
from core.easing import interpolate

# Progress from 0.0 to 1.0
t = i / (num_frames - 1)

# Apply easing
y = interpolate(start=0, end=400, t=t, easing='ease_out')

# Available: linear, ease_in, ease_out, ease_in_out,
#           bounce_out, elastic_out, back_out
```

### Frame Helpers (`core.frame_composer`)
Convenience functions for common needs:
```python
from core.frame_composer import (
    create_blank_frame,         # Solid color background
    create_gradient_background,  # Vertical gradient
    draw_circle,                # Helper for circles
    draw_text,                  # Simple text rendering
    draw_star                   # 5-pointed star
)
```

## Animation Concepts

### Shake/Vibrate
Offset object position with oscillation:
- Use `math.sin()` or `math.cos()` with frame index
- Add small random variations for natural feel
- Apply to x and/or y position

### Pulse/Heartbeat
Scale object size rhythmically:
- Use `math.sin(t * frequency * 2 * math.pi)` for smooth pulse
- For heartbeat: two quick pulses then pause (adjust sine wave)
- Scale between 0.8 and 1.2 of base size

### Bounce
Object falls and bounces:
- Use `interpolate()` with `easing='bounce_out'` for landing
- Use `easing='ease_in'` for falling (accelerating)
- Apply gravity by increasing y velocity each frame

### Spin/Rotate
Rotate object around center:
- PIL: `image.rotate(angle, resample=Image.BICUBIC)`
- For wobble: use sine wave for angle instead of linear

### Fade In/Out
Gradually appear or disappear:
- Create RGBA image, adjust alpha channel
- Or use `Image.blend(image1, image2, alpha)`
- Fade in: alpha from 0 to 1
- Fade out: alpha from 1 to 0

### Slide
Move object from off-screen to position:
- Start position: outside frame bounds
- End position: target location
- Use `interpolate()` with `easing='ease_out'` for smooth stop
- For overshoot: use `easing='back_out'`

### Zoom
Scale and position for zoom effect:
- Zoom in: scale from 0.1 to 2.0, crop center
- Zoom out: scale from 2.0 to 1.0
- Can add motion blur for drama (PIL filter)

### Explode/Particle Burst
Create particles radiating outward:
- Generate particles with random angles and velocities
- Update each particle: `x += vx`, `y += vy`
- Add gravity: `vy += gravity_constant`
- Fade out particles over time (reduce alpha)

## Optimization Strategies

Only when asked to make the file size smaller, implement a few of the following methods:

1. **Fewer frames** - Lower FPS (10 instead of 20) or shorter duration
2. **Fewer colors** - `num_colors=48` instead of 128
3. **Smaller dimensions** - 128x128 instead of 480x480
4. **Remove duplicates** - `remove_duplicates=True` in save()
5. **Emoji mode** - `optimize_for_emoji=True` auto-optimizes

```python
# Maximum optimization for emoji
builder.save(
    'emoji.gif',
    num_colors=48,
    optimize_for_emoji=True,
    remove_duplicates=True
)
```

## Philosophy

This skill provides:
- **Knowledge**: Slack's requirements and animation concepts
- **Utilities**: GIFBuilder, validators, easing functions
- **Flexibility**: Create the animation logic using PIL primitives

It does NOT provide:
- Rigid animation templates or pre-made functions
- Emoji font rendering (unreliable across platforms)
- A library of pre-packaged graphics built into the skill

**Note on user uploads**: This skill doesn't include pre-built graphics, but if a user uploads an image, use PIL to load and work with it - interpret based on their request whether they want it used directly or just as inspiration.

Be creative! Combine concepts (bouncing + rotating, pulsing + sliding, etc.) and use PIL's full capabilities.

## Dependencies

```bash
pip install pillow imageio numpy
```

Run this skill on a real model without leaving the page. Every run is saved to your history for this skill.

How to use

1. 1Save the content below as SKILL.md in your agent's skills directory (e.g. .claude/skills/<name>/SKILL.md).
2. 2Or paste it directly into the conversation as context before asking the agent to do the task.
3. 3Adjust any project-specific paths or conventions mentioned in the skill to match your setup.