/* Bring up a window and manipulate the gamma on it */

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <math.h>

#include "SDL.h"

/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */

static void quit(int rc)

{

	SDL_Quit();

	exit(rc);

}

/* Turn a normal gamma value into an appropriate gamma ramp */

void CalculateGamma(double gamma, Uint16 *ramp)

{

	int i, value;

	gamma = 1.0 / gamma;

	for ( i=0; i<256; ++i ) {

		value = (int)(pow((double)i/256.0, gamma)*65535.0 + 0.5);

		if ( value > 65535 ) {

			value = 65535;

		}

		ramp[i] = (Uint16)value;

	}

}

/* This can be used as a general routine for all of the test programs */

int get_video_args(char *argv[], int *w, int *h, int *bpp, Uint32 *flags)

{

	int i;

	*w = 640;

	*h = 480;

	*bpp = 0;

	*flags = SDL_SWSURFACE;

	for ( i=1; argv[i]; ++i ) {

		if ( strcmp(argv[i], "-width") == 0 ) {

			if ( argv[i+1] ) {

				*w = atoi(argv[++i]);

			}

		} else

		if ( strcmp(argv[i], "-height") == 0 ) {

			if ( argv[i+1] ) {

				*h = atoi(argv[++i]);

			}

		} else

		if ( strcmp(argv[i], "-bpp") == 0 ) {

			if ( argv[i+1] ) {

				*bpp = atoi(argv[++i]);

			}

		} else

		if ( strcmp(argv[i], "-fullscreen") == 0 ) {

			*flags |= SDL_FULLSCREEN;

		} else

		if ( strcmp(argv[i], "-hw") == 0 ) {

			*flags |= SDL_HWSURFACE;

		} else

		if ( strcmp(argv[i], "-hwpalette") == 0 ) {

			*flags |= SDL_HWPALETTE;

		} else

			break;

	}

	return i;

}

int main(int argc, char *argv[])

{

	SDL_Surface *screen;

	SDL_Surface *image;

	float gamma;

	int i;

	int w, h, bpp;

	Uint32 flags;

	Uint16 ramp[256];

	Uint16 red_ramp[256];

	Uint32 then, timeout;

	/* Check command line arguments */

	argv += get_video_args(argv, &w, &h, &bpp, &flags);

	/* Initialize SDL */

	if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {

		fprintf(stderr,

			"Couldn't initialize SDL: %s\n", SDL_GetError());

		return(1);

	}

	/* Initialize the display, always use hardware palette */

	screen = SDL_SetVideoMode(w, h, bpp, flags | SDL_HWPALETTE);

	if ( screen == NULL ) {

		fprintf(stderr, "Couldn't set %dx%d video mode: %s\n",

						w, h, SDL_GetError());

		quit(1);

	}

	/* Set the window manager title bar */

	SDL_WM_SetCaption("SDL gamma test", "testgamma");

	/* Set the desired gamma, if any */

	gamma = 1.0f;

	if ( *argv ) {

		gamma = (float)atof(*argv);

	}

	if ( SDL_SetGamma(gamma, gamma, gamma) < 0 ) {

		fprintf(stderr, "Unable to set gamma: %s\n", SDL_GetError());

		quit(1);

	}

#if 0 /* This isn't supported.  Integrating the gamma ramps isn't exact */

	/* See what gamma was actually set */

	float real[3];

	if ( SDL_GetGamma(&real[0], &real[1], &real[2]) < 0 ) {

		printf("Couldn't get gamma: %s\n", SDL_GetError());

	} else {

		printf("Set gamma values: R=%2.2f, G=%2.2f, B=%2.2f\n",

			real[0], real[1], real[2]);

	}

#endif

	/* Do all the drawing work */

	image = SDL_LoadBMP("sample.bmp");

	if ( image ) {

		SDL_Rect dst;

		dst.x = (screen->w - image->w)/2;

		dst.y = (screen->h - image->h)/2;

		dst.w = image->w;

		dst.h = image->h;

		SDL_BlitSurface(image, NULL, screen, &dst);

		SDL_UpdateRects(screen, 1, &dst);

	}

	/* Wait a bit, handling events */

	then = SDL_GetTicks();

	timeout = (5*1000);

	while ( (SDL_GetTicks()-then) < timeout ) {

		SDL_Event event;

		while ( SDL_PollEvent(&event) ) {

			switch (event.type) {

			    case SDL_QUIT:	/* Quit now */

				timeout = 0;

				break;

			    case SDL_KEYDOWN:

				switch (event.key.keysym.sym) {

				    case SDLK_SPACE:	/* Go longer.. */

					timeout += (5*1000);

					break;

				    case SDLK_UP:

					gamma += 0.2f;

					SDL_SetGamma(gamma, gamma, gamma);

					break;

				    case SDLK_DOWN:

					gamma -= 0.2f;

					SDL_SetGamma(gamma, gamma, gamma);

					break;

				    case SDLK_ESCAPE:

					timeout = 0;

					break;

				    default:

					break;

				}

				break;

			}

		}

	}

	/* Perform a gamma flash to red using color ramps */

	while ( gamma < 10.0 ) {

		/* Increase the red gamma and decrease everything else... */

		gamma += 0.1f;

		CalculateGamma(gamma, red_ramp);

		CalculateGamma(1.0/gamma, ramp);

		SDL_SetGammaRamp(red_ramp, ramp, ramp);

	}

	/* Finish completely red */

	memset(red_ramp, 255, sizeof(red_ramp));

	memset(ramp, 0, sizeof(ramp));

	SDL_SetGammaRamp(red_ramp, ramp, ramp);

	/* Now fade out to black */

	for ( i=(red_ramp[0] >> 8); i >= 0; --i ) {

		memset(red_ramp, i, sizeof(red_ramp));

		SDL_SetGammaRamp(red_ramp, NULL, NULL);

	}

	SDL_Delay(1*1000);

	SDL_Quit();

	return(0);

}