Two steps...
The specific settings require experimentation, particularly depending on whether it's screen resolution or print.
? Filter > Artistic > Poster Edges...
Edge Thickness: 5
?Edge Intensity: 4
Posterization: 3
?Filter > Artistic > Cutout...
No. of Levels: 7
Edge Simplicity: 0
Edge Fidelity: 1
You can do this in PS CS Filter Factory in a single two layer step.
The specific settings require experimentation, particularly depending on whether it's screen resolution or print.
? Filter > Artistic > Poster Edges...
Edge Thickness: 5
?Edge Intensity: 4
Posterization: 3
?Filter > Artistic > Cutout...
No. of Levels: 7
Edge Simplicity: 0
Edge Fidelity: 1
You can do this in PS CS Filter Factory in a single two layer step.