Adjust brightness and contrast of BufferedImage in Java
That was easy, actually.
RescaleOp rescaleOp = new RescaleOp(1.2f, 15, null);
rescaleOp.filter(image, image); // Source and destination are the same.
A scaleFactor of 1.2 and offset of 15 seems to make the image about a stop brighter.
Yay!
Read more in the docs for RescaleOp.