view src/video/SDL_gamma.c @ 1050:8e1815fd9777

Holding down shift while moving the mouse's scrollwheel on MacOS X makes the OS report these are "horizontal scrollwheel" events, which confuses gaming apps in several legitimate conditions. Now all scrollwheel events are made to look vertical when passed to the app. Patch by John Knottenbelt. http://www.libsdl.org/pipermail/sdl/2005-March/067978.html
author Ryan C. Gordon <icculus@icculus.org>
date Sun, 17 Apr 2005 10:32:41 +0000
parents b8d311d90021
children c9b51268668f
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 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@libsdl.org
*/

#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 <string.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(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 ) {
		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;
}