在AndroidStudio中res目录，右键->Convert to WebP，可以将此目录中的图片转换为WebP格式，由于项目中图片数目比较多，转换后，对比观测apk总体小了4M左右。
| 打包模式 | 转换前 | 转换后 | 缩小 |
|---|---|---|---|
| debug | 75.2MB | 71.1MB | 4.1MB |
| release | 64MB | 60.5MB | 3.5MB |
WebP is a modern image format that provides superior lossless and lossy compression for images on the web. Using WebP, webmasters and web developers can create smaller, richer images that make the web faster.
WebP lossless images are 26% smaller in size compared to PNGs. WebP lossy images are 25-34% smaller than comparable JPEG images at equivalent SSIM quality index.
关于apk的大小，官方有一篇文章详细介绍了如何操作，可参考 Shrink your app
