Double Choco (Off-by-One) (1256)

Change each given number to be 1 more or 1 less, then:
Divide the grid into regions along grid lines. Each region must contain exactly one group of orthogonally connected white cells and exactly one group of orthogonally connected gray cells. Both connected groups must form the same shape (rotations and reflections are allowed). Each number indicates the area of the group (not region) that number is in. (Regions might contain no numbers, or multiple given numbers, even in the same color.)

Reference: WPF (1)