Mercurial > sdl-ios-xcode
view src/video/SDL_gamma.c @ 1554:0ca607a5d173
Fixed bug #84
Date: Sun, 23 Oct 2005 16:39:03 +0200
From: "A. Schmid" <sahib@phreaker.net>
Subject: [SDL] no software surfaces with svgalib driver?
Hi,
I noticed that the SDL (1.2.9) svgalib driver only makes use of linear
addressable (framebuffer) video modes. On older systems (like one of
mine), linear addressable modes are often not available.
Especially for cards with VESA VBE < 2.0 the svgalib vesa driver is
unusable, since VESA only supports framebuffering for VBE 2.0 and later.
The changes necessary to add support for software surfaces seem to be
relatively small. I only had to hack src/video/svga/SDL_svgavideo.c (see
attached patch). The code worked fine for me, but it is no more than a
proof of concept and should be reviewed (probably has a memory leak when
switching modes). It also uses the vgagl library (included in the
svgalib package) and needs to be linked against it.
-Alex
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sun, 19 Mar 2006 12:04:40 +0000 |
parents | d910939febfa |
children | 97d0966f4bf7 |
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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 <= 0.0 ) { 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); } } 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; }