Create new layer, fill with white, move white layer BELOW layer with black dots, then merge all layers (Ctrl-Shift-E).
Go to effects - Blur - Gaussian blur, apply blur with about 3-4 pixels.
Open Levels (Ctrl-L) and adjust them carefully
Remove white. You might know how to do it from my previous tutorials, so in short:
- select all (Ctrl-A)
- copy (Ctrl-C)
- turn on quick mask (Q)
- paste (Ctrl-V)
- turn off quick mask (Q)
- remove selection (Del)
- make layer black (Ctrl-U, set Lightness to -100%).
Now copy black dots to our wallpaper, and invert (Ctrl-I) to make dots white.