Diffuse Glow will generate diffuse glows.
EditByBSEditor: Diffuse Glow is a photoshop filter that will generate diffuse glows.

DESCRIPTION:
This filter produces diffused glows.
Threshold: This slider controls the tolerance for selection.
Any Pixels brighter than the threshold will be selected for glowing.
Radius: This slider controls the size of the glow.
Low numbers are recommended for strong glows while higher numbers for softer ones.
Intensity: This slider controls the strength (in percent) of the glow.
0 produces no glow, 100 maximum glow.
Selection: This variable specifies the method in which intensity is calculated for selecting.
(R+G+B)/3: Red, Green and Blue are added together and then averaged.
Red, Green & Blue: The intensity is derived from the respective color channel.
XYZITU, XYZ709, XYZ601-1: The intensity is derived from the respective grayscale conversion.
(R+G)/2: The intensity is derived from the Red and Green channels averaged.
(G+B)/2: The intensity is derived from the Green and Blue channels averaged.
(B+R)/2: The intensity is derived from the Blue and Red channels averaged.
Diffusion: This specifies the type of diffusion to use.
Box Blur: This is a FASTER blur, but begins looking boxy at higher values.
Gaussian Blur: This is a slower but cleaner blur, especially at higher values.
Display: Displays the full output effect, the selection only, or the diffused only.
This is useful for working with the isolated effect.
Output: Controls which channels to output.
This is useful for colored glows.
Realtime: Applies all effects (in realtime) on mouse drag instead of on mouse release. you can free download Diffuse Glow 1.5 now.