--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/video/SDL_gamma.c	Thu Apr 26 16:45:43 2001 +0000
@@ -0,0 +1,242 @@
+/*
+    SDL - Simple DirectMedia Layer
+    Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 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
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public
+    License along with this library; if not, write to the Free
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+    Sam Lantinga
+    slouken@devolution.com
+*/
+
+#ifdef SAVE_RCSID
+static char rcsid =
+ "@(#) $Id$";
+#endif
+
+/* Gamma correction support */
+
+#define USE_MATH_H	/* Used for calculating gamma ramps */
+
+#ifdef USE_MATH_H
+#include <math.h>
+#endif
+#include <stdlib.h>
+
+#include "SDL_error.h"
+#include "SDL_sysvideo.h"
+
+#ifdef USE_MATH_H
+static 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 /* USE_MATH_H */
+
+int SDL_SetGamma(float red, float green, float blue)
+{
+	int succeeded;
+	SDL_VideoDevice *video = current_video;
+	SDL_VideoDevice *this  = current_video;	
+
+	succeeded = -1;
+#ifdef USE_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 = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]);
+	}
+#else
+	SDL_SetError("Gamma correction not supported");
+#endif
+	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;
+#ifdef USE_MATH_H
+	/* 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]);
+		}
+	}
+#else
+	SDL_SetError("Gamma correction not supported");
+#endif
+	if ( (succeeded < 0) && video->GetGamma ) {
+		SDL_ClearError();
+		succeeded = video->GetGamma(this, red, green, blue);
+	}
+	return succeeded;
+}
+
+int SDL_SetGammaRamp(Uint16 *red, Uint16 *green, 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 ) {
+		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 & 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 = 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 ) {
+		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;
+}