/***  $Id: gamma.c,v 1.4 2003/11/23 05:10:59 weiym Exp $**  **  Port to MiniGUI by Wei Yongming (2001/10/03).**  Copyright (C) 2001 ~ 2002 Wei Yongming.**  Copyright (C) 2003 Feynman Software.****  SDL - Simple DirectMedia Layer**  Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga*//*** This program is free software; you can redistribute it and/or modify** it under the terms of the GNU General Public License as published by** the Free Software Foundation; either version 2 of the License, or** (at your option) any later version.**** This program 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 General Public License for more details.**** You should have received a copy of the GNU General Public License** along with this program; if not, write to the Free Software** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA*//* Gamma correction support */#include <stdio.h>#include <stdlib.h>#include <string.h>#include "common.h"#ifdef HAVE_MATH_H#include <math.h>#endif#include "newgal.h"#include "sysvideo.h"#ifdef HAVE_MATH_Hstatic void CalculateGammaRamp(float gamma, Uint16 *ramp){	int i;	/* 0.0 gamma is all black */	if ( gamma <= 0.0 ) {		for ( i=0; i<256; ++i ) {			ramp[i] = 0;		}		return;	} else	/* 1.0 gamma is identity */	if ( gamma == 1.0 ) {		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 = 0.0;	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 ) {		*gamma = 1.0f / (sum / count);	}}#endif /* HAVE_MATH_H */int GAL_SetGamma(float red, float green, float blue){	int succeeded;	GAL_VideoDevice *video = current_video;	GAL_VideoDevice *this  = current_video;		succeeded = -1;#ifdef HAVE_MATH_H	/* 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 = GAL_SetGammaRamp(ramp[0], ramp[1], ramp[2]);	}#else	GAL_SetError("Gamma correction not supported");#endif	if ( (succeeded < 0) && video->SetGamma ) {		GAL_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 GAL_GetGamma(float *red, float *green, float *blue){	int succeeded;	GAL_VideoDevice *video = current_video;	GAL_VideoDevice *this  = current_video;		succeeded = -1;#ifdef HAVE_MATH_H	/* Prefer using GetGammaRamp(), as it's more flexible */	{		Uint16 ramp[3][256];		succeeded = GAL_GetGammaRamp(ramp[0], ramp[1], ramp[2]);		if ( succeeded >= 0 ) {			CalculateGammaFromRamp(red, ramp[0]);			CalculateGammaFromRamp(green, ramp[1]);			CalculateGammaFromRamp(blue, ramp[2]);		}	}#else	GAL_SetError("Gamma correction not supported");#endif	if ( (succeeded < 0) && video->GetGamma ) {		GAL_ClearError();		succeeded = video->GetGamma(this, red, green, blue);	}	return succeeded;}int GAL_SetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue){	int succeeded;	GAL_VideoDevice *video = current_video;	GAL_VideoDevice *this  = current_video;		GAL_Surface *screen = GAL_PublicSurface;	/* Verify the screen parameter */	if ( !screen ) {		GAL_SetError("No video mode has been set");		return -1;	}	/* Lazily allocate the gamma tables */	if ( ! video->gamma ) {		GAL_GetGammaRamp(0, 0, 0);	}	/* Fill the gamma table with the new values */	if ( red ) {		memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma));	}	if ( green ) {		memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma));	}	if ( blue ) {		memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma));	}	/* Gamma correction always possible on split palettes */	if ( (screen->flags & GAL_HWPALETTE) == GAL_HWPALETTE ) {		GAL_Palette *pal = screen->format->palette;		/* If physical palette has been set independently, use it */		if(video->physpal)		        pal = video->physpal;		      		GAL_SetPalette(screen, GAL_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 {		GAL_SetError("Gamma ramp manipulation not supported");	}	return succeeded;}int GAL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue){	GAL_VideoDevice *video = current_video;	GAL_VideoDevice *this  = current_video;		/* Lazily allocate the gamma table */	if ( ! video->gamma ) {		video->gamma = malloc(3*256*sizeof(*video->gamma));		if ( ! video->gamma ) {			GAL_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 ) {		memcpy(red, &video->gamma[0*256], 256*sizeof(*red));	}	if ( green ) {		memcpy(green, &video->gamma[1*256], 256*sizeof(*green));	}	if ( blue ) {		memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue));	}	return 0;}