The PixelFormat enum in the web engine is incomplete. According to https://api.flutter.dev/flutter/dart-ui/PixelFormat.html and the native engine, we are supposed to have a rgbaFloat32 option as well. In flutter/engine#42019 I added support for it in Skwasm, but it remains unsupported in the other renderers, as well as in the BMP creation code path.