145 lines
3.5 KiB
Markdown
145 lines
3.5 KiB
Markdown
# Image Processing Commands
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These are specific examples for cases where the user needs concrete commands rather than only decision guidance.
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## ImageMagick
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### Resize
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```bash
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magick input.jpg -resize 1920x1080\> output.jpg
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magick input.jpg -resize 800x600! output.jpg
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```
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### Format Conversion
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```bash
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magick input.jpg -quality 80 output.webp
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magick input.png -background white -flatten output.jpg
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magick input.jpg -quality 75 output.avif
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```
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### Orientation and Metadata
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```bash
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magick input.jpg -auto-orient output.jpg
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magick input.jpg -auto-orient -strip output.jpg
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identify -verbose input.jpg | grep -i exif
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```
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### SVG Optimization and Rasterization
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```bash
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npx svgo input.svg -o output.svg
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magick -background none -density 300 input.svg -resize 512x512 output.png
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```
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### Batch Processing
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```bash
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mogrify -format webp -quality 80 *.jpg
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mogrify -resize 1920x1080\> *.jpg
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```
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### Aspect-Ratio Crop
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```bash
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magick input.jpg -gravity center -crop 1200x630+0+0 +repage output.jpg
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magick input.jpg -resize 1200x630^ -gravity center -extent 1200x630 output.jpg
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```
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## Pillow
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### Resize
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```python
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from PIL import Image
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img = Image.open("input.jpg")
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img = img.resize((800, 600), Image.Resampling.LANCZOS)
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img.save("output.jpg", quality=85)
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```
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### WebP Conversion
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```python
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from PIL import Image
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img = Image.open("input.jpg")
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img.save("output.webp", "WEBP", quality=80, method=6)
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```
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### Transparency to White Background
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```python
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from PIL import Image
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img = Image.open("input.png")
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if img.mode in ("RGBA", "LA", "P"):
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background = Image.new("RGB", img.size, (255, 255, 255))
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background.paste(img, mask=img.split()[-1] if img.mode == "RGBA" else None)
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img = background
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img.save("output.jpg", quality=85)
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```
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### Thumbnail
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```python
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from PIL import Image
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img = Image.open("input.jpg")
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img.thumbnail((300, 300), Image.Resampling.LANCZOS)
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img.save("thumb.jpg", quality=75)
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```
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## Built-in and Alternative Tools
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### macOS `sips`
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```bash
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sips -Z 1600 input.jpg --out output.jpg
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sips -s format webp input.png --out output.webp
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```
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- Useful when Pillow or ImageMagick are unavailable.
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- Validate quality and metadata handling because `sips` is convenient, not always the most controllable.
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### Sharp (Node.js)
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```bash
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npx sharp input.jpg --resize 1600 --webp quality=80 -o output.webp
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npx sharp input.png --flatten background=white --jpeg quality=85 -o output.jpg
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```
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- Good for scripted web pipelines and batch conversions.
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- Still inspect transparency flattening, color handling, and output dimensions deliberately.
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### `exiftool`
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```bash
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exiftool input.jpg
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exiftool -gps:all= -overwrite_original input.jpg
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exiftool -all= -overwrite_original input.jpg
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```
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- Useful when metadata handling is the real job.
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- Prefer targeted stripping when rights data or timestamps still matter.
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### `ffmpeg` for Animated Images
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```bash
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ffmpeg -i input.gif -vf "fps=15,scale=1200:-1:flags=lanczos" output.webm
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ffmpeg -i input.gif -vf "fps=15,scale=1200:-1:flags=lanczos" -loop 0 output.webp
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```
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- Better than treating every animation problem as a GIF problem forever.
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## Command Traps
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- Always auto-orient before final export if EXIF rotation exists.
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- Flatten alpha intentionally when converting transparent images to JPEG.
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- Use `LANCZOS` for final downscaling, not low-quality defaults.
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- Spot-check one file before running a batch command across everything.
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- Prefer writing outputs to a new path instead of overwriting the only good source.
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- Treat `npx` examples as remote-code execution from the package registry and use them only in trusted environments.
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