c# - Getting brightness of displayed screen or of a Texture2D - Unity3D -

in project, need brightness of screen being displayed. that, snapshot of screen , make texture2d

to snapshot , convert use this:

public void getscreen(ref texture2d screenshot){         rendertexture rt = new rendertexture(screen.width, screen.height, 24);         camera.targettexture = rt;         screenshot = new texture2d(screen.width, screen.height, textureformat.rgb24, false);         camera.render();         rendertexture.active = rt;         screenshot.readpixels(new rect(0, 0, sreen.width, screen.height), 0, 0);         camera.targettexture = null;         rendertexture.active = null;         destroy(rt); } 

but still need brightness.
suggestions accepted (about brightness and/or conversion).
in advance.

once have pixels, next step use pixels on image sample of them , build brightness them: http://docs.unity3d.com/documentation/scriptreference/texture2d.getpixel.html

determining brightness bit of complex issue, depends on application. formula determine brightness of rgb color has methods determine brightness of single pixel. sample several pixels towards center of image, , take average of those.

if need more complex solution, build histogram of pixels brightness, , find peak. http://en.wikipedia.org/wiki/image_histogram .