ldpi

0.75x

mdpi

1.0x

hdpi

1.5x

xhdpi

2.0x

xxhdpi

3.0x

xxxhdpi

4.0x

Assets are located in any arbitrary folder—
Flutter has no predefined folder structure.
You declare the assets (with location)
in the pubspec.yaml file, and Flutter picks them up.

To add a new image asset called my_icon.png to our Flutter project,
for example, and deciding that it should live in a folder we
arbitrarily called images, you would put the base image (1.0x)
in the images folder, and all the other variants in sub-folders
called with the appropriate ratio multiplier: