/* gcc -o xbright xbright.c -I/usr/X11R6/include -L/usr/X11R6/lib -lX11 -lXext -lXxf86vm -lm
*/
#include <X11/Xlib.h>
#include <X11/extensions/Xext.h>
#include <X11/extensions/xf86vmode.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define GAMMA_COMPONENTS 3
#define GAMMA_RESOLUTION 256

#define MAX_RAMP 65535

Display *dpy;
unsigned short ramp_in[GAMMA_COMPONENTS][GAMMA_RESOLUTION];

int main(int argc, char *argv[])
{
	unsigned short ramp_out[GAMMA_COMPONENTS][GAMMA_RESOLUTION];
	int x, y;

	double gamma;
	int min, max;

	--argc;

	if (argc == 0) {
		gamma = 1.0;
		min = 0;
		max = MAX_RAMP;
	} else if (argc != 3) {
		fprintf(stderr, "%s gamma black white\n", argv[0]);
		exit(-1);
	} else {
		gamma = strtod(argv[1], NULL);
		min = strtol(argv[2], NULL, 0);
		max = strtol(argv[3], NULL, 0);	
	}

	printf("gamma = %f\nblack = %d\nwhite = %d\n", gamma, min, max);
	
	dpy = XOpenDisplay(NULL);
	if (!XF86VidModeGetGammaRamp(dpy, DefaultScreen(dpy), GAMMA_RESOLUTION, ramp_in[0], ramp_in[1], ramp_in[2]))
		return 1;
	
	gamma = 1.0 / gamma;
	for (x = 0; x < GAMMA_COMPONENTS; x++)
		for (y = 0; y < GAMMA_RESOLUTION; y++)
			ramp_out[x][y] = min + pow((y/255.0), gamma) * (max-min);
	
	if (!XF86VidModeSetGammaRamp(dpy, DefaultScreen(dpy), GAMMA_RESOLUTION, ramp_out[0], ramp_out[1], ramp_out[2]))
		return 1;

	return 0;
}