# Only Exporting Certain Layers
One use case that the `psd` crate is designed to support is an asset pipeline where you're extracting image data from PSD files in order to convert it into the format that your
application works with (such as PNG).
In order to support that use case we grant control over exactly which layers in your PSD get exported via the [flatten_layers_rgba][flatten-fn] funcion.
You provide a filter function and any layers that pass your filter (return true) will get blended from top to bottom into a final image.
Here's an example of compositing a final image from layers that do not have names that begin with an underscore.
```rust,no_run,ignore
let psd = include_bytes!("./my-psd-file.psd");
let pixels: Vec<u8> = psd.flatten_layers_rgba(&|(_idx, layer) {
!layer.name().started_with("_")
}).unwrap();
```
[flatten-fn]: https://chinedufn.github.io/psd/api/psd/struct.Psd.html#method.flatten_layers_rgba