The best way to brighten any image without destroying it, is gamma up the magnitude.

The traditional methods of brightening ie photoshop, are gain & gamma, gain/brightness will blow out the image and clip it, gamma up will wash out and desaturate the image.

A better method is to seperate the color component from the "energy" (magnitude) of the pixels and gamma the "energy" up, then re-insert it into the image.

Consider the image rgb as a vector rgb = xyz, scaling the magnitude will not change the angle of the vector, or in the image's case the relationship of r,g,b to each other., like this:

magnitude = sqrt(r*r + g*g + b*b);

r_tmp = r/mag;

g_tmp = g/mag;

b_tmp = b/mag;

mag_tmp = powf(magnitude, 1.0/gamma);

r = r*mag_tmp;

g = g*mag_tmp;

b = b*mag_tmp;

return r,g,b;

here's my method vs traditional methods: