Compress Images

Image Compression Skill

Compress all images in $ARGUMENTS (or app/assets/images/content/ if no path provided) to WebP format, optimized for SEO performance (target: under 100KB per image).

Process

1. Create originals folder - Create originals/ subfolder inside the target directory and move source files there. Never destroy source files.
2. Compress each image (JPG, PNG, GIF) from originals/ to the parent directory as .webp
3. Iterate until all images are under 100KB - check sizes after each pass, re-compress any that exceed the target
4. Report results with before/after sizes
5. Update references in content files from old extensions to .webp

File Structure

target-directory/
├── originals/           # High-quality source files preserved here
│   ├── hero.jpg
│   └── feature.png
├── hero.webp            # Compressed, web-optimized
└── feature.webp

Iterative Compression Algorithm

IMPORTANT: Keep compressing until ALL images are under 100KB. Check sizes after each pass and re-compress any that exceed the target.

Step 1: Initial pass (q 70)

cwebp -q 70 -resize 1200 0 originals/image.jpg -o image.webp
ls -lh image.webp  # Check size

Step 2: If still over 100KB, reduce quality progressively

# Try these in order until under 100KB:
cwebp -q 60 -resize 1200 0 originals/image.jpg -o image.webp
cwebp -q 50 -resize 1200 0 originals/image.jpg -o image.webp
cwebp -q 45 -resize 1200 0 originals/image.jpg -o image.webp
cwebp -q 40 -resize 1200 0 originals/image.jpg -o image.webp
cwebp -q 35 -resize 1200 0 originals/image.jpg -o image.webp

Step 3: For stubborn images, also reduce dimensions

# If q 35 at 1200px is still over 100KB, reduce to 1000px:
cwebp -q 30 -resize 1000 0 originals/image.jpg -o image.webp
cwebp -q 25 -resize 1000 0 originals/image.jpg -o image.webp

Real-World Results (Reference)

From actual compression run on content images:

| Image | Original | First Try | Final | Settings Used | |-------|----------|-----------|-------|---------------| | waves.jpg | 198KB | 33KB | 33KB | q 70, 1200px (1 pass) | | calendar.jpg | 246KB | 42KB | 42KB | q 70, 1200px (1 pass) | | floating.jpg | 230KB | 43KB | 43KB | q 70, 1200px (1 pass) | | cash.jpg | 409KB | 88KB | 88KB | q 70, 1200px (1 pass) | | knot.jpg | 395KB | 96KB | 96KB | q 70, 1200px (1 pass) | | floating-dark.jpg | 414KB | 94KB | 94KB | q 70, 1200px (1 pass) | | keyboard2.jpg | 459KB | 102KB | 102KB | q 70, 1200px (1 pass, acceptable) | | perpetual.jpg | 565KB | 130KB | 96KB | q 40, 1200px (3 passes) | | keyboard.jpg | 718KB | 196KB | 98KB | q 25, 1000px (5 passes) |

Key Insights

1. Most images (under 500KB source) compress fine with default settings (q 70, 1200px)
2. Large detailed images (500KB+) often need multiple passes
3. Very large images (700KB+) may need both lower quality AND smaller dimensions
4. Keyboard/tech photos with fine detail are hardest to compress - expect 4-5 passes
5. Soft/blurry images compress much better than sharp detailed ones

After Compression

1. Verify ALL files under 100KB: ls -lh *.webp - re-run compression on any exceeding target
2. Update content files referencing old extensions (.jpg, .png) to use .webp
3. Test that images render correctly in the application
4. Original files remain in originals/ folder for future reference or re-compression

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: rameerez
• Source: rameerez/claude-code-startup-skills
• License: MIT

Install and usage instructions live in the source repository linked above.