Mercurial > sdl-ios-xcode
view src/video/SDL_gamma.c @ 4142:4433ef2a1802 SDL-1.2
We probably want to still do this for fullscreen surfaces, since we may be
clearing the edges of a centered video mode or garbage left over from a mode
switch.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Fri, 29 Feb 2008 14:01:45 +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; }