This is an OK method for a quick edit.
But you get a lot of color-loss. You can see in the purple in this image is gone on the scaling up.
Spoiler, click to toggle visibilty
(http://i.imgur.com/BA0czEy.png)
One suggestion would be, because the sprites are probably already paletted and use maybe 32 colors, use the magic wand (photoshop) and set the tolerance to 2 or 3. The smaller the more accurate, but the more clicks you'll have to do. Click each purple until ALL of the purple is selected. Then cut(ctrl+x) and paste (ctrl+v) into a new layer. Once each part of the spark is separated apply the Gaussian blur to each layer. Use ctrl+e to combine all the layers back into one, and save as your png or whatever.
This is my attempt. I did the first image the way I mentioned, and then did it the original way
Spoiler, click to toggle visibilty
(http://i.imgur.com/bPOuYIL.png)
You can still see a couple problems. I didn't do the large canvas size like the tutorial says. So this is proof you NEED to do it. You can really tell at the bottom. But if you want the green and the blue, adding the few simple steps helps.
This is an OK method for a quick edit.
But you get a lot of color-loss. You can see in the purple in this image is gone on the scaling up.
Spoiler, click to toggle visibilty
(http://i.imgur.com/BA0czEy.png)
One suggestion would be, because the sprites are probably already paletted and use maybe 32 colors, use the magic wand (photoshop) and set the tolerance to 2 or 3. The smaller the more accurate, but the more clicks you'll have to do. Click each purple until ALL of the purple is selected. Then cut(ctrl+x) and paste (ctrl+v) into a new layer. Once each part of the spark is separated apply the Gaussian blur to each layer. Use ctrl+e to combine all the layers back into one, and save as your png or whatever.
This is my attempt. I did the first image the way I mentioned, and then did it the original way
Spoiler, click to toggle visibilty
(http://i.imgur.com/bPOuYIL.png)
You can still see a couple problems. I didn't do the large canvas size like the tutorial says. So this is proof you NEED to do it. You can really tell at the bottom. But if you want the green and the blue, adding the few simple steps helps.
I don't mean in this an offensive way, but you said his method is OK, but your one is worse.
First, did you change the background colour to black?
Second, you didn't increase the image size (you already stated this)
Third, You seem to be using the same colour palette that the original one had? bad idea
Lastly, by separating the layers and then applying Gaussian blur is a bad idea because each separation will be outlined with what ever background you have.
I hope I explained this OK.
I have always wanted to make an update to P.O.T.S original post. I think Memo's method is that absolute basic and quick way to do it, but neither gimp or photoshop are the 'best' method to imitate P.O.T.S hi res effects.