Can I apply the same effect to an individual element instead of a group?

Checking for non-cached images

Caching an image with RepaintBoundary is good,
when it makes sense.

One of the most expensive operations,
from a resource perspective,
is rendering a texture using an image file.
First, the compressed image
is fetched from persistent storage.
The image is decompressed into host memory (GPU memory),
and transferred to device memory (RAM).

In other words, image I/O can be expensive.
The cache provides snapshots of complex hierarchies so
they are easier to render in subsequent frames.
Because raster cache entries are expensive to
construct and take up loads of GPU memory,
cache images only where absolutely necessary.

You can see which images are being cached by enabling the
PerformanceOverlayLayer.checkerboardRasterCacheImages switch.