How is this image conversion achieved?

[Colin ST]

Been seeing a few images recently (usually old 8-bit computer game covers) that have been retouched and cleaned up from the originals. I know that they are not redrawn from scratch in Photoshop or Illustrator, so I assume it's either done by hand or some kind of plugin/action is being used.

Here's an example of what I'm talking about. The original game cover is on the left and the cleaned-up version is on the right. I'd love to be able to do something similar with some of my old comic collections.

[PBArtattack]

Try some adjustment layers. I hit the left side of your screenshot with Vibrance and then threw in some Photo Filter with a bit of masking to cool the results down a bit.

[Trevor.Dennis]

Wow.  You are never going to get the image on the left looking like the one on the right using filters, adjusment layers, black magic and CSI plugins.  Look how clean the line work is?  See how smooth and fluid the gradients are?  Someone has spent a lot of time making the one on the right look that nice.  There's a clue in the added detail.  There's two or three hours work in that.

[c.pfaffenbichler]

Just as an example that manual inpot seems practically unavoidable in such a case: 

There seems to be no detail in large parts of the »bubble« on the left so the result appears to have included some painting.