[PvK]

If you want to edit the file, and you have a program [such as Photoshop or MS Photo Editor (comes with some Versions of Office)] which allows changing the "Gamma" of the image, that can also easily make it brighter in one simple step.

Of course, if you like the images but just want to brighten the digits and text, you can just brighten the plain rectangle (second position from left, bottom half).

PvK