animated-message-composer（动画消息编辑器）

Slack GIF Creator

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

Slack Requirements

Emoji GIFs (Slack emoji uploads):

• Max size: 64 KB
• Dimensions: 128x128 recommended (square)
• FPS: 10-12
• Colors: 32-48
• Duration: 1-2s

Message GIFs:

• Max size: ~2 MB
• Dimensions: 480x480 typical
• FPS: 15-20
• Colors: 128-256
• Duration: 2-5s

Core Workflow

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)

Optional shortcut: use animation templates in templates/ to generate frames quickly:

from templates.shake import create_shake_animation

frames = create_shake_animation(
    object_type='circle',
    object_data={'radius': 30, 'color': (100, 150, 255)},
    num_frames=20,
    direction='both'
)
builder.add_frames(frames)

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:

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:

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)

Avoid relying solely on emoji fonts: they are platform-specific. If you use draw_emoji or draw_emoji_enhanced, expect rendering differences and be ready to adjust with shapes or text.

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:

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:

from core.validators import (
    validate_gif,
    is_slack_ready,
    check_slack_size,
    validate_dimensions
)

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

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

# Focused checks
passes, info = check_slack_size('my.gif', is_emoji=True)
passes, info = validate_dimensions(128, 128, is_emoji=True)

Easing Functions (core.easing)

Smooth motion instead of linear:

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:

from core.frame_composer import (
    create_blank_frame,         # Solid color background
    create_gradient_background,  # Vertical gradient
    draw_circle,                # Helper for circles
    draw_rectangle,             # Helper for rectangles
    draw_line,                  # Helper for lines
    draw_text,                  # Simple text rendering
    draw_emoji,                 # Emoji rendering (platform-dependent)
    draw_star                   # 5-pointed star
)

Other helpers include draw_emoji_enhanced, draw_circle_with_shadow, draw_rounded_rectangle, and add_vignette.

Color Palettes (core.color_palettes)

Hand-picked palettes and helpers for readable colors:

from core.color_palettes import get_palette, get_text_color_for_background

palette = get_palette('vibrant')
text_color = get_text_color_for_background(palette['background'])

Typography (core.typography)

High-quality outlined or shadowed text:

from core.typography import draw_text_with_outline

draw_text_with_outline(frame, "SALE!", position=(240, 240), font_size=48, centered=True)

Visual Effects (core.visual_effects)

Particles, blur, impacts, and motion effects:

from core.visual_effects import ParticleSystem

particles = ParticleSystem()
particles.emit(240, 240, count=20)

Animation Templates (templates/)

Ready-made animations (shake, bounce, spin, zoom, slide, fade, flip, explode, etc.). Use them to generate frames and then pass to GIFBuilder.

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

# 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

pip install pillow imageio numpy