Save uint8list as 24 bit rgb png - flutter

Question

I am creating custom images with flutters canvas and need them to be saved as 24 bit (rgb) pngs without the alpha channel.
I am using the flutter_file_dialog package for the image export.
But the final images are saved in the 32 bit format (rgba).
I have searched the flutter documentation but have not found an easy way to remove the alpha channel.
Would I have to do the removal myself by changing the uint8list?
import 'dart:ui' as ui;
Future<void> createImage() async {
final recorder = ui.PictureRecorder();
const Size size = Size(2000, 2000);
final Rect rect = Rect.fromLTRB(0, 0, size.width, size.height);
final canvas = Canvas(recorder, rect);
// canvas design ...
// capture canvas and save it as image
final picture = recorder.endRecording();
ui.Image newImage = await picture.toImage(size.width.toInt(), size.height.toInt());
ByteData pngBytes = await newImage.toByteData(format: ui.ImageByteFormat.png);
Uint8List uint8list = Uint8List.view(pngBytes.buffer);
// export the image
final params = SaveFileDialogParams(fileName: "image.png", data: uint8list);
final filePath = await FlutterFileDialog.saveFile(params: params);
}