nm-scry-gif-generation（nm scry gif 生成）

Night Market Skill — ported from claude-night-market/scry. For the full experience with agents, hooks, and commands, install the Claude Code plugin.

Table of Contents

• Overview
• Required TodoWrite Items
• Process
• Step 1: Validate Input File
• Step 2: Check ffmpeg Installation
• Step 3: Execute Conversion
• Basic Conversion (Fast, Larger File))
• High Quality with Palette Generation (Recommended))
• Maximum Quality with Dithering
• Optimization Options
• Common Presets
• Step 4: Verify Output
• Exit Criteria
• Troubleshooting
• Large Output File
• Color Banding
• Slow Conversion

GIF Generation Skill

Post-process video files (webm/mp4) and generate optimized GIF output with configurable quality settings.

When To Use

• Converting recordings to animated GIF format
• Creating lightweight demo animations

When NOT To Use

• High-quality video output - use full recording tools
• Static image generation without animation needs

Overview

This skill handles the conversion of video recordings (typically from browser automation) to GIF format. It provides multiple quality presets and optimization options to balance file size with visual quality.

Required TodoWrite Items

- Validate input video file exists
- Check ffmpeg installation
- Execute GIF conversion
- Verify output and report results

Verification: Run the command with --help flag to verify availability.

Process

Step 1: Validate Input File

Confirm the source video file exists and is a supported format:

# Check file exists and get info
if [[ -f "$INPUT_FILE" ]]; then
    file "$INPUT_FILE"
    ffprobe -v quiet -show_format -show_streams "$INPUT_FILE" 2>/dev/null | head -20
else
    echo "Error: Input file not found: $INPUT_FILE"
    exit 1
fi

Verification: Run the command with --help flag to verify availability.

Supported input formats: .webm, .mp4, .mov, .avi

Step 2: Check ffmpeg Installation

Verify ffmpeg is available:

if ! command -v ffmpeg &> /dev/null; then
    echo "Error: ffmpeg is not installed"
    echo "Install with: sudo apt install ffmpeg (Linux) or brew install ffmpeg (macOS)"
    exit 1
fi
ffmpeg -version | head -1

Verification: Run the command with --help flag to verify availability.

Step 3: Execute Conversion

Choose the appropriate conversion command based on quality requirements:

Basic Conversion (Fast, Larger File)

ffmpeg -i input.webm -vf "fps=10,scale=800:-1" output.gif

Verification: Run the command with --help flag to verify availability.

High Quality with Palette Generation (Recommended)

ffmpeg -i input.webm -vf "fps=10,scale=800:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" output.gif

Verification: Run the command with --help flag to verify availability.

Maximum Quality with Dithering

ffmpeg -i input.webm -vf "fps=15,scale=1024:-1:flags=lanczos,split[s0][s1];[s0]palettegen=max_colors=256:stats_mode=single[p];[s1][p]paletteuse=dither=bayer:bayer_scale=5" output.gif

Verification: Run the command with --help flag to verify availability.

Optimization Options

Common Presets

# Thumbnail (small, fast loading)
ffmpeg -i input.webm -vf "fps=8,scale=480:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" thumbnail.gif

# Documentation (balanced)
ffmpeg -i input.webm -vf "fps=10,scale=800:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" docs.gif

# High-fidelity demo
ffmpeg -i input.webm -vf "fps=15,scale=1024:-1:flags=lanczos,split[s0][s1];[s0]palettegen=max_colors=256[p];[s1][p]paletteuse" demo.gif

Verification: Run the command with --help flag to verify availability.

Step 4: Verify Output

Confirm successful conversion and report metrics:

if [[ -f "$OUTPUT_FILE" ]]; then
    echo "GIF generated successfully: $OUTPUT_FILE"

    # Report file size
    SIZE=$(du -h "$OUTPUT_FILE" | cut -f1)
    echo "File size: $SIZE"

    # Get dimensions and frame count
    ffprobe -v quiet -select_streams v:0 -show_entries stream=width,height,nb_frames -of csv=p=0 "$OUTPUT_FILE"
else
    echo "Error: GIF generation failed"
    exit 1
fi

Verification: Run the command with --help flag to verify availability.

Exit Criteria

• [ ] Input file validated as existing video format
• [ ] ffmpeg confirmed available
• [ ] GIF file created at specified output path
• [ ] Output file size reported to user
• [ ] No ffmpeg errors during conversion

Troubleshooting

Large Output File

Reduce quality settings:

# Lower fps and resolution
ffmpeg -i input.webm -vf "fps=8,scale=640:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" smaller.gif

Verification: Run the command with --help flag to verify availability.

Color Banding

Use dithering:

ffmpeg -i input.webm -vf "fps=10,scale=800:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse=dither=floyd_steinberg" smooth.gif

Verification: Run the command with --help flag to verify availability.

Slow Conversion

Use basic conversion without palette generation for speed:

ffmpeg -i input.webm -vf "fps=10,scale=800:-1" quick.gif

Verification: Run the command with --help flag to verify availability.