view src/video/SDL_gamma.c @ 4016:3f93ccc2c01e SDL-1.2

Clear the NOFRAME and RESIZABLE flags in the X11 target before setting their new values, so multiple calls to SetVideoMode() that toggle these will end up with the right data. Fixes Bugzilla #441.
author Ryan C. Gordon <icculus@icculus.org>
date Sun, 08 Jul 2007 01:50:26 +0000
parents 65800e7f7146
children c121d94672cb a1b03ba2fcd0
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* Gamma correction support */

#ifdef HAVE_MATH_H
#include <math.h>	/* Used for calculating gamma ramps */
#else
/* Math routines from uClibc: http://www.uclibc.org */
#include "math_private.h"
#include "e_sqrt.h"
#include "e_pow.h"
#include "e_log.h"
#define pow(x, y)	__ieee754_pow(x, y)
#define log(x)		__ieee754_log(x)
#endif

#include "SDL_sysvideo.h"


static void CalculateGammaRamp(float gamma, Uint16 *ramp)
{
	int i;

	/* 0.0 gamma is all black */
	if ( gamma <= 0.0f ) {
		for ( i=0; i<256; ++i ) {
			ramp[i] = 0;
		}
		return;
	} else
	/* 1.0 gamma is identity */
	if ( gamma == 1.0f ) {
		for ( i=0; i<256; ++i ) {
			ramp[i] = (i << 8) | i;
		}
		return;
	} else
	/* Calculate a real gamma ramp */
	{ int value;
		gamma = 1.0f / 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;
		}
	}
}
static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp)
{
	/* The following is adapted from a post by Garrett Bass on OpenGL
	   Gamedev list, March 4, 2000.
	 */
	float sum = 0.0f;
	int i, count = 0;

	*gamma = 1.0;
	for ( i = 1; i < 256; ++i ) {
	    if ( (ramp[i] != 0) && (ramp[i] != 65535) ) {
	        double B = (double)i / 256.0;
	        double A = ramp[i] / 65535.0;
	        sum += (float) ( log(A) / log(B) );
	        count++;
	    }
	}
	if ( count && sum > 0.0f ) {
		*gamma = 1.0f / (sum / count);
	}
}

int SDL_SetGamma(float red, float green, float blue)
{
	int succeeded;
	SDL_VideoDevice *video = current_video;
	SDL_VideoDevice *this  = current_video;	

	succeeded = -1;
	/* Prefer using SetGammaRamp(), as it's more flexible */
	{
		Uint16 ramp[3][256];

		CalculateGammaRamp(red, ramp[0]);
		CalculateGammaRamp(green, ramp[1]);
		CalculateGammaRamp(blue, ramp[2]);
		succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]);
	}
	if ( (succeeded < 0) && video->SetGamma ) {
		SDL_ClearError();
		succeeded = video->SetGamma(this, red, green, blue);
	}
	return succeeded;
}

/* Calculating the gamma by integrating the gamma ramps isn't exact,
   so this function isn't officially supported.
*/
int SDL_GetGamma(float *red, float *green, float *blue)
{
	int succeeded;
	SDL_VideoDevice *video = current_video;
	SDL_VideoDevice *this  = current_video;	

	succeeded = -1;
	/* Prefer using GetGammaRamp(), as it's more flexible */
	{
		Uint16 ramp[3][256];

		succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]);
		if ( succeeded >= 0 ) {
			CalculateGammaFromRamp(red, ramp[0]);
			CalculateGammaFromRamp(green, ramp[1]);
			CalculateGammaFromRamp(blue, ramp[2]);
		}
	}
	if ( (succeeded < 0) && video->GetGamma ) {
		SDL_ClearError();
		succeeded = video->GetGamma(this, red, green, blue);
	}
	return succeeded;
}

int SDL_SetGammaRamp(const Uint16 *red, const Uint16 *green, const Uint16 *blue)
{
	int succeeded;
	SDL_VideoDevice *video = current_video;
	SDL_VideoDevice *this  = current_video;	
	SDL_Surface *screen = SDL_PublicSurface;

	/* Verify the screen parameter */
	if ( !screen ) {
		SDL_SetError("No video mode has been set");
		return -1;
	}

	/* Lazily allocate the gamma tables */
	if ( ! video->gamma ) {
		SDL_GetGammaRamp(0, 0, 0);
	}

	/* Fill the gamma table with the new values */
	if ( red ) {
		SDL_memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma));
	}
	if ( green ) {
		SDL_memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma));
	}
	if ( blue ) {
		SDL_memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma));
	}

	/* Gamma correction always possible on split palettes */
	if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) {
		SDL_Palette *pal = screen->format->palette;

		/* If physical palette has been set independently, use it */
		if(video->physpal)
		        pal = video->physpal;
		      
		SDL_SetPalette(screen, SDL_PHYSPAL,
			       pal->colors, 0, pal->ncolors);
		return 0;
	}

	/* Try to set the gamma ramp in the driver */
	succeeded = -1;
	if ( video->SetGammaRamp ) {
		succeeded = video->SetGammaRamp(this, video->gamma);
	} else {
		SDL_SetError("Gamma ramp manipulation not supported");
	}
	return succeeded;
}

int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue)
{
	SDL_VideoDevice *video = current_video;
	SDL_VideoDevice *this  = current_video;	

	/* Lazily allocate the gamma table */
	if ( ! video->gamma ) {
		video->gamma = SDL_malloc(3*256*sizeof(*video->gamma));
		if ( ! video->gamma ) {
			SDL_OutOfMemory();
			return -1;
		}
		if ( video->GetGammaRamp ) {
			/* Get the real hardware gamma */
			video->GetGammaRamp(this, video->gamma);
		} else {
			/* Assume an identity gamma */
			int i;
			for ( i=0; i<256; ++i ) {
				video->gamma[0*256+i] = (i << 8) | i;
				video->gamma[1*256+i] = (i << 8) | i;
				video->gamma[2*256+i] = (i << 8) | i;
			}
		}
	}

	/* Just copy from our internal table */
	if ( red ) {
		SDL_memcpy(red, &video->gamma[0*256], 256*sizeof(*red));
	}
	if ( green ) {
		SDL_memcpy(green, &video->gamma[1*256], 256*sizeof(*green));
	}
	if ( blue ) {
		SDL_memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue));
	}
	return 0;
}