GIMP/Add a Shine to Buttons

What the Effect Looks Like
The effect will produce something like this:



Design the Button


For this button I selected all, then did Image>Select>Rounded Rectangle, with a radius of 50. I filled it with red, then I selected the border and filled with a darker red.

Add a New Layer for the Shine
Create a new layer (call it shine or something similar), then select the whole region of your button (If you created it on a new layer you can right click on the layer and select “Alpha to Selection”), next shrink the selection (Image>Select>Shrink), how much you want to shrink it depends on the size of the image, for mine I used 6px, then fill the selection with white.



Now, you have a big ugly white spot in your image, how will that be turned into a shine? First, turn the layer transparency down to about 80%, this is found in the layers dialogue



Turn the Ugly Spot into a Shine
First, add a layer mask, and select fill with black. (Full transparency).



Then go to the gradient tool and select linear white to black gradient, (make sure you are editing the layer mask-- it should have a white border around it in the layers dialogue), draw a gradient from wherever you want the shine to start (Top-left corner in the example) to about the middle, feel free to experiment.



ADD
Once you are done you may add another layer for drawing on, or put text on, for the example I added the text “ADD”.