How can I add transparent background on this image instead of black background, but I also would like to keep the partial transparency effect on some of the particles and particles borders.
Could you please share actions in either photoshop or gimp, thanks.
Greenfish Icon Editor Pro has this functionality out of the box. It is a function called "Remove Matte", where you just specify the color component you want to be replaced with transparency. In your case black.
This is the result:
Greenfish Icon Editor Pro is totally free of charge. It is by far the best free icon editor I have ever tried. From the description of the product on the download site:
GFIE Pro is a powerful icon, cursor, animation and icon library editor. Layer support with advanced selection handling makes it a really professional and unique freeware tool for designing small pixelgraphic images. GFIE offers high-quality filters like Bevel, Drop Shadow and Glow; supports editing animated cursors and managing icon libraries. It's lightweight (< 1.8 MB unzipped) and also has a portable version - just unpack it to your USB drive and use it anywhere. A clean, customizable, multilanguage user interface makes it really easy to learn and use.
And just to be complete, here is the GIMP answer.
if "Color to Alpha ..." is greyed out you need to set the Image mode to something else than indexed, e.g.: