mirror of https://github.com/GNOME/gimp.git
101 lines
2.4 KiB
C
101 lines
2.4 KiB
C
/* GIMP - The GNU Image Manipulation Program
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* Copyright (C) 1995 Spencer Kimball and Peter Mattis
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "config.h"
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#include <glib-object.h>
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#include "libgimpmath/gimpmath.h"
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#include "libgimpbase/gimpbase.h"
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#include "base-types.h"
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#include "curves.h"
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#include "gimplut.h"
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/* public functions */
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void
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curves_init (Curves *curves)
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{
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GimpHistogramChannel channel;
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g_return_if_fail (curves != NULL);
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for (channel = GIMP_HISTOGRAM_VALUE;
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channel <= GIMP_HISTOGRAM_ALPHA;
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channel++)
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{
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gint j;
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for (j = 0; j < 256; j++)
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curves->curve[channel][j] = j;
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}
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}
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gfloat
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curves_lut_func (Curves *curves,
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gint n_channels,
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gint channel,
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gfloat value)
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{
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gfloat f;
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gint index;
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gdouble inten;
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gint j;
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if (n_channels <= 2)
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j = channel;
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else
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j = channel + 1;
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inten = value;
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/* For RGB and RGBA images this runs through the loop with j = channel + 1
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* the first time and j = 0 the second time
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*
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* For GRAY images this runs through the loop with j = 0 the first and
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* only time
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*/
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for (; j >= 0; j -= (channel + 1))
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{
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/* don't apply the overall curve to the alpha channel */
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if (j == 0 && (n_channels == 2 || n_channels == 4) &&
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channel == n_channels - 1)
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return inten;
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if (inten < 0.0)
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{
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inten = curves->curve[j][0]/255.0;
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}
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else if (inten >= 1.0)
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{
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inten = curves->curve[j][255]/255.0;
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}
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else /* interpolate the curve */
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{
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index = floor (inten * 255.0);
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f = inten * 255.0 - index;
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inten = ((1.0 - f) * curves->curve[j][index ] +
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f * curves->curve[j][index + 1] ) / 255.0;
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}
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}
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return inten;
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}
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