RGB pallet manipulation - blackout and light-up effects

I'm working with Turbo C++ in 13h mode (256 colors) and what I want to do is make a function(s) that would either light-up the entire screen (just like turning up the brightness for all colors) or blackout (all colors going to black). So what I want to know is what's a good algorithm for both? I've written a few functions, for example for the light-up function I would just take the current RGB value for a color and increment all three colors by 1, but that tends to mess up the actual picture (like if one of the colors is at the max already then the other two would increase by them selves changing the actual color and not only the brightness). Any good ideas?

You have to move them relative and not absolule. If the original color is 0 / 128 / 255 you have to increase the colors by 1.0 / 0.5 / 0.0 understand the system? So the movement is ( 1 - (Original / 255) ) for each, R, G and B.

In that case, if I have picturebox control and I want to do that on the picture. So, how could I use BitBlt or anything else to succeed? :confused:

BitBlt won't help you on this.. You'll have to go thru each pixel and modulate the color..

Go it all working great. Thanks.

Hehe very well, this is a bit unfinished but you get the point (didn’t finish the ending sequence). Just a program that I'm making for my final project in my C++ class, no real point though. To quit press Esc and you will see why I wanted these 2 effects. Also, there are 2 versions that I've compiled, for some unknown reason (at least to me) the text memory offset (I'm using direct text output - writing to memory) needs to be changed on some computers. For most computers RACE1.EXE should work fine, but if you see that the text is in the wrong position when you start the program, then try RACE2. Maybe you know why this is? I'm using pokeb() function and address B800 : offset to output the text to the screen yet on my computer the offset for the first character on the screen is 32 instead of 0 as it is on most computers I’ve tried this on. :confused:

Well any way, here are the programs:
http://www.tnstop.com/RACE1.EXE
http://www.tnstop.com/RACE2.EXE

I can give you the source if you'd like, but I hate commenting, so it might kinda hard to understand.

Oh and also if you use + and - keys (-/=) you can adjust the speed - I was bored :D

I had to use the RACE2 one. If it helps, I'm running a Celeron/Win2000/GF2MX.

Hm...so far what I'm noticing is that any system running Win2k or XP (what I use) has to use the second one, while systems on Win 98 (at my school) use the first one. Strange...