Marta Bondyra 65bdf1ff8e

Optimize existing image assets with lossless compression (#223998) ...

## Summary

This PR applies **lossless compression** to all SVG and JPG/PNG assets
across Kibana using:

- [`svgo`](https://github.com/svg/svgo) — for optimizing SVGs  
- [`image-optimize`](https://www.npmjs.com/package/image-optimize) — for
JPG/PNG compression

‼️**Please scroll to ''Unknown metric groups" accordion to see what's
the gain for your code.**
<img width="542" alt="Screenshot 2025-06-18 at 13 24 20"
src="https://github.com/user-attachments/assets/191afb28-44fc-4551-9026-756a8385c66a"
/>

The goal is to reduce asset size and improve load performance without
compromising visual quality.

This PR achieves a **23 MB** reduction in asset size across all images
bundled in Kibana’s running code—meaning these compressed images
directly impact what ships in Kibana.
Some assets get bundled into chunks due to our bundling strategy but
might not actually be requested at runtime.

Additionally, I ran the same optimization script on the docs assets as a
harmless extra step, but those savings aren’t included in the 23 MB
total.

---

## Why

While working on Emotion rewrites, I noticed some SVGs seemed
unnecessarily heavy. That led to a broader investigation into our image
assets, and it turns out we’re not consistently optimizing them during
development or build.


---

## Notes

- Visual fidelity of optimized assets has been manually verified — no
visible differences
- The optimization is **lossless**, meaning no quality degradation
- Some assets (like large background images) could benefit further from
**lossy compression**

---

## Follow-ups / Ideas

1. **Automate compression in the dev/build pipeline**
   - e.g. add `svgo` as a pre-commit or CI step for SVGs
2. **Improve CI reporting**  
- Currently, bundle size diffs for images are hidden under "Unknown
metric groups" in the GitHub CI comment. We may want to make these more
visible.
   - 
3. **Audit large assets manually** — apply lossy compression where
appropriate
4. **Avoid redundant image loading**  
- e.g. background images on the login page are loaded again on the space
selector page since they’re bundled twice. I’m working on a separate PR
to address that.

## Snippets I used to apply the compression

```
# Find SVG files
find . -type f -iname "*.svg" \
  -not -path "*/node_modules/*" \
  -not -path "*/functional/*" > svg-files.txt

# Compress SVGs
while IFS= read -r file; do
  svgo "$file"
done < svg-files.txt
```

This snippet has been used for png and jpg, but the example below is for
png:
```
# Find PNG files
find . -type f -iname "*.png \
  -not -path "*/node_modules/*" \
  -not -path "*/functional/*" > png-files.txt

# Compress PNGs
while IFS= read -r file; do
  image-optimize -f jpg "$file"
done < png-files.txt
```

2025-06-19 16:44:13 +02:00

23 KiB

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