Image Processing
Use img-process (shipped in bin/) for common operations. For complex or custom workflows, generate a Pillow script adapted to the user's environment.
Quick Reference — img-process CLI
img-process resize hero.png --width 1920
img-process convert logo.png --format webp
img-process trim logo-raw.jpg -o logo-clean.png --padding 10
img-process thumbnail photo.jpg --size 200
img-process optimise hero.jpg --quality 85 --max-width 1920
img-process og-card -o og.png --title "My App" --subtitle "Built for speed"
img-process batch ./images --action convert --format webp -o ./optimised
Use img-process when: the operation is standard (resize, convert, trim, thumbnail, optimise, OG card, batch). This is faster and avoids generating a script each time.
Generate a custom script when: the operation needs logic img-process doesn't cover (compositing multiple images, watermarks, complex text layouts, conditional processing).
Prerequisites
Pillow is required for both img-process and custom scripts:
pip install Pillow
If Pillow is unavailable, use alternatives:
| Alternative | Platform | Install | Best for |
|---|
sips | macOS (built-in) | None | Resize, convert (no trim/OG) |
sharp | Node.js | npm install sharp | Full feature set, high performance |
ffmpeg | Cross-platform | brew install ffmpeg | Resize, convert |
Output Format Guide
| Use case | Format | Why |
|---|
| Photos, hero images | WebP | Best compression, wide browser support |
| Logos, icons (need transparency) | PNG | Lossless, supports alpha |
| Fallback for older browsers | JPG | Universal support |
| Thumbnails | WebP or JPG | Small file size priority |
| OG cards | PNG | Social platforms handle PNG best |
Core Patterns
Save with Format-Specific Quality
Different formats need different save parameters. Always handle RGBA-to-JPG compositing — JPG does not support transparency, so composite onto a white background first.
from PIL import Image
import os
def save_image(img, output_path, quality=None):
os.makedirs(os.path.dirname(output_path) or ".", exist_ok=True)
kwargs = {}
ext = output_path.lower().rsplit(".", 1)[-1]
if ext == "webp":
kwargs = {"quality": quality or 85, "method": 6}
elif ext in ("jpg", "jpeg"):
kwargs = {"quality": quality or 90, "optimize": True}
# RGBA → RGB: composite onto white background
if img.mode == "RGBA":
bg = Image.new("RGB", img.size, (255, 255, 255))
bg.paste(img, mask=img.split()[3])
img = bg
elif ext == "png":
kwargs = {"optimize": True}
img.save(output_path, **kwargs)
Resize with Aspect Ratio
When only width or height is given, calculate the other from aspect ratio. Use Image.LANCZOS for high-quality downscaling.
def resize_image(img, width=None, height=None):
if width and height:
return img.resize((width, height), Image.LANCZOS)
elif width:
ratio = width / img.width
return img.resize((width, int(img.height * ratio)), Image.LANCZOS)
elif height:
ratio = height / img.height
return img.resize((int(img.width * ratio), height), Image.LANCZOS)
return img
Trim Whitespace (Auto-Crop)
Remove surrounding whitespace from logos and icons. Convert to RGBA first, then use getbbox() to find content bounds.
img = Image.open(input_path)
if img.mode != "RGBA":
img = img.convert("RGBA")
bbox = img.getbbox() # Bounding box of non-zero pixels
if bbox:
img = img.crop(bbox)
Thumbnail
Fit within max dimensions while maintaining aspect ratio:
img.thumbnail((size, size), Image.LANCZOS)
Optimise for Web
Resize + compress in one step. Convert to WebP for best compression. Typical settings: width 1920, quality 85.
Cross-Platform Font Discovery
System font paths differ by OS. Try multiple paths, fall back to Pillow's default. On Linux, fc-list can discover fonts dynamically.
from PIL import ImageFont
def get_font(size):
font_paths = [
# macOS
"/System/Library/Fonts/Helvetica.ttc",
"/System/Library/Fonts/SFNSText.ttf",
# Linux
"/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",
"/usr/share/fonts/truetype/liberation/LiberationSans-Regular.ttf",
# Windows
"C:/Windows/Fonts/arial.ttf",
]
for path in font_paths:
if os.path.exists(path):
try:
return ImageFont.truetype(path, size)
except Exception:
continue
return ImageFont.load_default()
OG Card Generation (1200x630)
Composite text on a background image or solid colour. Apply semi-transparent overlay for text readability. Centre text horizontally.
from PIL import Image, ImageDraw, ImageFont
width, height = 1200, 630
# Background: image or solid colour
if background_path:
img = Image.open(background_path).resize((width, height), Image.LANCZOS)
else:
img = Image.new("RGB", (width, height), bg_color or "#1a1a2e")
# Semi-transparent overlay for text readability
overlay = Image.new("RGBA", (width, height), (0, 0, 0, 128))
img = img.convert("RGBA")
img = Image.alpha_composite(img, overlay)
draw = ImageDraw.Draw(img)
font_title = get_font(48)
font_sub = get_font(24)
# Centre title
if title:
bbox = draw.textbbox((0, 0), title, font=font_title)
tw = bbox[2] - bbox[0]
draw.text(((width - tw) // 2, height // 2 - 60), title, fill="white", font=font_title)
img = img.convert("RGB")
Common Workflows
Logo Cleanup (client-supplied JPG with white background)
img-process trim logo-raw.jpg -o logo-trimmed.png --padding 10
img-process thumbnail logo-trimmed.png --size 512 -o favicon-512.png
Prepare Hero Image for Production
img-process optimise hero.jpg --max-width 1920 --quality 85
# Outputs hero.webp — resized and compressed
Batch Process
img-process batch ./raw-images --action convert --format webp --quality 85 -o ./optimised
img-process batch ./photos --action resize --width 800 -o ./thumbnails
Pipeline with Gemini Image Gen
Generate images with the gemini-image-gen skill, then process them:
# After generating with Gemini (raw PNG output):
img-process optimise generated-image.png --max-width 1920 --quality 85
# Or batch process all generated images:
img-process batch ./generated --action optimise -o ./production