In Painer you can create a solid emanating background or overlay emanating light on top of an object.The picture on the right is an example of the latter case.
First, open the picture to be overlayed. If there are several layers in the picture. Choose Clone from File to make a one-layered picture, otherwise the emanation will be put in the background rather than on top of the object.
Choose Grad from Art Materials. The first five icons show the default or the lastest choices you picked. To unveil more effects, click on the down arrow, which is located inside the blue bar. When you select a choice, the icon goes up to one of the first five boxes.
You can dail the red round button on the ring and press the recentage buttons at the bottom to alter the orientation of the gradiation. The red button controls the rotation of the emanation whereas the recentage buttons control the density (how many rays of light).
After you set up the orientation of the emanation, choose Fill from Effects. From there you can adjust the transparency of the emanation.
If the effect is too dark, you still have a second chance to fix it. You can choose Fade from Edit to partially undo the effect. In other words, you can make the emanation more transparent.
This write-up will illustrate how a similar effect is created in PhotoShop.