Media Compression Skill#

Compress and convert images and videos with intelligent defaults. Supports single files and batch processing.

Supported Formats#

Images: JPG, PNG, WebP, BMP, TIFF, GIF → JPG, PNG, WebP Videos: MP4, MOV, AVI, MKV, WebM, FLV, WMV, M4V → MP4

Prerequisites#

ffmpeg must be installed:

• Ubuntu/Debian: sudo apt update && sudo apt install ffmpeg
• macOS: brew install ffmpeg
• Windows: Download from https://ffmpeg.org/download.html and add to PATH

Verify installation: ffmpeg -version

Quick Start#

Image Compression#

bash

# Compress to target size (auto-adjusts quality)
python scripts/compress_image.py photo.jpg --max-size 200kb

# Resize + compress
python scripts/compress_image.py photo.png --width 800 --output photo_small.jpg

# Convert to WebP (better compression)
python scripts/compress_image.py photo.jpg --format webp

# Batch compress entire folder
python scripts/compress_image.py ./photos --output ./compressed --quality 80

# Preview mode - see what will happen without compressing
python scripts/compress_image.py photo.jpg --max-size 500kb --preview

# Keep backup of original file
python scripts/compress_image.py photo.jpg --max-size 500kb --backup

Video Compression#

bash

# Compress with default settings (good balance)
python scripts/compress_video.py video.mp4 --output video_small.mp4

# Resize to 720p
python scripts/compress_video.py video.mp4 --height 720

# Target specific file size (approximate)
python scripts/compress_video.py video.mp4 --target-size 50mb

# Lower quality for smaller file
python scripts/compress_video.py video.mp4 --crf 28

# Batch process all videos in folder
python scripts/compress_video.py ./videos --output ./compressed --height 480

# Preview mode - see what will happen without compressing
python scripts/compress_video.py video.mp4 --height 720 --preview

# Keep backup of original file
python scripts/compress_video.py video.mp4 --height 720 --backup

Common Use Cases#

1. Upload to Website (Image)#

Most websites need images under 500KB:

bash

python scripts/compress_image.py photo.jpg --max-size 500kb --format webp

2. Email Attachment (Image)#

Email often has 25MB limit:

bash

python scripts/compress_image.py scan.pdf.jpg --max-size 5mb --quality 90

3. Social Media Video#

Platforms prefer 720p, smaller files:

bash

python scripts/compress_video.py clip.mov --height 720 --crf 23 --preset fast

4. Archive Old Videos#

Maximum compression for storage:

bash

python scripts/compress_video.py old_video.avi --crf 28 --preset slow --height 480

5. Convert Format Only#

Keep quality, just change format:

bash

# Image
python scripts/compress_image.py image.png --format jpg --quality 95

# Video
python scripts/compress_video.py video.mov --output video.mp4 --crf 18

Parameters Reference#

Image ( compress_image.py)#

ParameterDescriptionDefaultinputInput file or directory (required)---output, -oOutput file or directoryAuto-generated--max-sizeTarget max file size (e.g., 500kb, 2mb)None--quality, -qJPEG/WebP quality (1-100)85--width, -wMax width in pixelsOriginal--heightMax height in pixelsOriginal--format, -fOutput format: jpg, png, webpOriginal format--no-stripKeep metadata (default: remove)False--preview, -pPreview mode: show settings without compressingFalse--backup, -bKeep backup of original fileFalse

Video ( compress_video.py)#

ParameterDescriptionDefaultinputInput file or directory (required)---output, -oOutput file or directoryAuto-generated--crfQuality 0-51 (lower=better). 18=visually lossless, 23=default, 28=smaller23--presetEncoding speed: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslowmedium--heightMax height (480, 720, 1080)Original--target-sizeApproximate target size (e.g., 50mb, 1gb)None--fpsLimit frame rate (e.g., 30, 24)Original--audio-bitrateAudio quality (e.g., 128k, 192k)128k--preview, -pPreview mode: show settings without compressingFalse--backup, -bKeep backup of original fileFalse

Quality Guidelines#

Images#

• 90-95: High quality, minimal compression artifacts
• 85: Sweet spot (default) - good quality, significant size reduction
• 70-80: Acceptable for web, smaller files
• 50-60: Low quality, visible artifacts

Videos (CRF)#

• 17-18: Visually lossless, archival quality
• 20-22: High quality, professional use
• 23: Default, good balance (recommended)
• 28: Smaller files, acceptable quality
• 35+: Low quality, preview/draft only

Presets#

• ultrafast: Fastest encoding, largest files
• fast: Quick results, slightly larger
• medium: Default balance
• slow: Better compression, smaller files
• veryslow: Maximum compression, smallest files

Batch Processing#

When input is a directory:

• All supported files are processed
• Output directory structure mirrors input
• Progress shown for each file
• Original and compressed sizes displayed

Example:

bash

$ python scripts/compress_image.py ./vacation_photos --output ./compressed --max-size 500kb
找到 24 个图像文件
[1/24] 处理: IMG_001.jpg
  ✓ 2847.3KB → 456.2KB (84.0% 减少)
[2/24] 处理: IMG_002.png
  ✓ 1532.1KB → 298.5KB (80.5% 减少)
...

Troubleshooting#

"ffmpeg not found"#

Install ffmpeg first:

bash

# Ubuntu/Debian
sudo apt update && sudo apt install ffmpeg

# macOS
brew install ffmpeg

"Permission denied"#

Make scripts executable:

bash

chmod +x scripts/*.py

Quality too low#

Increase quality setting:

bash

# Image
python scripts/compress_image.py photo.jpg --quality 90

# Video
python scripts/compress_video.py video.mp4 --crf 20

File not smaller#

• Try lower quality or smaller dimensions
• Some files are already optimally compressed
• Use --max-size to force target size

Batch processing stops#

Check that all files in directory are valid images/videos. Corrupt files may cause errors.

Advanced Tips#

1. Strip metadata for privacy (default behavior)
2. Use WebP for best web compression
3. 720p height is usually enough for mobile viewing
4. CRF 23 + preset slow gives great results for archiving
5. Test with one file before batch processing

References#

• FFmpeg Guide - Detailed ffmpeg commands and parameters