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Diffstat (limited to 'source/blender/render/intern/source/gammaCorrectionTables.c')
| -rw-r--r-- | source/blender/render/intern/source/gammaCorrectionTables.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/source/blender/render/intern/source/gammaCorrectionTables.c b/source/blender/render/intern/source/gammaCorrectionTables.c new file mode 100644 index 00000000000..b25e7f0cdca --- /dev/null +++ b/source/blender/render/intern/source/gammaCorrectionTables.c @@ -0,0 +1,168 @@ +/** + * Jitter offset table + * + * $Id$ + * + * ***** BEGIN GPL/BL DUAL LICENSE BLOCK ***** + * + * 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. The Blender + * Foundation also sells licenses for use in proprietary software under + * the Blender License. See http://www.blender.org/BL/ for information + * about this. + * + * 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. + * + * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV. + * All rights reserved. + * + * The Original Code is: all of this file. + * + * Contributor(s): none yet. + * + * ***** END GPL/BL DUAL LICENSE BLOCK ***** + */ + +#include "gammaCorrectionTables.h" +#include <stdlib.h> +#include <math.h> + +#include "render_intern.h" + +/* There are two parts here: one for the old renderer, one for the unified */ +/* renderer. we start with the latter. */ + +/* Default gamma. For most CRTs, gamma ranges from 2.2 to 2.5 (Foley), so */ +/* 2.35 seems appropriate enough. Experience teaches a different number */ +/* though. Old blender: 2.0. It might be nice to make this a slider */ +#define RE_DEFAULT_GAMMA 2.0 +/* This 400 is sort of based on the number of intensity levels needed for */ +/* the typical dynamic range of a medium, in this case CRTs. (Foley) */ +/* (Actually, it says the number should be between 400 and 535.) */ +#define RE_GAMMA_TABLE_SIZE 400 + +/* These indicate the status of the gamma lookup table --------------------- */ + +static float gamma_range_table[RE_GAMMA_TABLE_SIZE + 1]; +static float gamfactor_table[RE_GAMMA_TABLE_SIZE]; +static float inv_gamma_range_table[RE_GAMMA_TABLE_SIZE + 1]; +static float inv_gamfactor_table[RE_GAMMA_TABLE_SIZE]; +static float colour_domain_table[RE_GAMMA_TABLE_SIZE + 1]; +static float colour_step; +static float inv_colour_step; +static float valid_gamma; +static float valid_inv_gamma; +static int gamma_table_initialised = 0; +static int do_gamma; +/* ------------------------------------------------------------------------- */ + +float gammaCorrect(float c) +{ + int i; + float res = 0.0; + + i = floor(c * inv_colour_step); + /* Clip to range [0,1]: outside, just do the complete calculation. */ + /* We may have some performance problems here. Stretching up the LUT */ + /* may help solve that, by exchanging LUT size for the interpolation. */ + /* Negative colours are explicitly handled. */ + if (i < 0) res = -pow(abs(c), valid_gamma); + else if (i >= RE_GAMMA_TABLE_SIZE ) res = pow(c, valid_gamma); + else res = gamma_range_table[i] + + ( (c - colour_domain_table[i]) * gamfactor_table[i]); + + return res; +} /* end of float gammaCorrect(float col) */ + +/* ------------------------------------------------------------------------- */ + +float invGammaCorrect(float col) +{ + int i; + float res = 0.0; + + i = floor(col*inv_colour_step); + /* Negative colours are explicitly handled. */ + if (i < 0) res = -pow(abs(col), valid_inv_gamma); + else if (i >= RE_GAMMA_TABLE_SIZE) res = pow(col, valid_inv_gamma); + else res = inv_gamma_range_table[i] + + ( (col - colour_domain_table[i]) * inv_gamfactor_table[i]); + + return res; +} /* end of float invGammaCorrect(float col) */ + + +/* ------------------------------------------------------------------------- */ + +void makeGammaTables(float gamma) +{ + /* we need two tables: one forward, one backward */ + int i; + + valid_gamma = gamma; + valid_inv_gamma = 1.0 / gamma; + colour_step = 1.0 / RE_GAMMA_TABLE_SIZE; + inv_colour_step = (float) RE_GAMMA_TABLE_SIZE; + + /* We could squeeze out the two range tables to gain some memory. */ + for (i = 0; i < RE_GAMMA_TABLE_SIZE; i++) { + colour_domain_table[i] = i * colour_step; + gamma_range_table[i] = pow(colour_domain_table[i], + valid_gamma); + inv_gamma_range_table[i] = pow(colour_domain_table[i], + valid_inv_gamma); + } + + /* The end of the table should match 1.0 carefully. In order to avoid */ + /* rounding errors, we just set this explicitly. The last segment may */ + /* have a different lenght than the other segments, but our */ + /* interpolation is insensitive to that. */ + colour_domain_table[RE_GAMMA_TABLE_SIZE] = 1.0; + gamma_range_table[RE_GAMMA_TABLE_SIZE] = 1.0; + inv_gamma_range_table[RE_GAMMA_TABLE_SIZE] = 1.0; + + /* To speed up calculations, we make these calc factor tables. They are */ + /* multiplication factors used in scaling the interpolation. */ + for (i = 0; i < RE_GAMMA_TABLE_SIZE; i++ ) { + gamfactor_table[i] = inv_colour_step + * (gamma_range_table[i + 1] - gamma_range_table[i]) ; + inv_gamfactor_table[i] = inv_colour_step + * (inv_gamma_range_table[i + 1] - inv_gamma_range_table[i]) ; + } + + gamma_table_initialised = 1; +} /* end of void makeGammaTables(float gamma) */ + +/* ------------------------------------------------------------------------- */ + +int gammaTableIsInitialised(void) +{ + return gamma_table_initialised; +} + +/* ------------------------------------------------------------------------- */ +int doGamma() +{ + return do_gamma; +} + +/* ------------------------------------------------------------------------- */ + +/** + * Set/unset performing gamma corrections. + */ +void setDoGamma(int i) +{ + do_gamma = i; +} + +/* eof */ |