mirror of https://github.com/GNOME/gimp.git
114 lines
3.1 KiB
C
114 lines
3.1 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 <cairo.h>
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#include <glib-object.h>
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#include "libgimpcolor/gimpcolor.h"
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#include "libgimpmath/gimpmath.h"
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#include "base-types.h"
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#include "levels.h"
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/* public functions */
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void
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levels_init (Levels *levels)
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{
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GimpHistogramChannel channel;
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g_return_if_fail (levels != 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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levels->gamma[channel] = 1.0;
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levels->low_input[channel] = 0;
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levels->high_input[channel] = 255;
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levels->low_output[channel] = 0;
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levels->high_output[channel] = 255;
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}
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}
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gfloat
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levels_lut_func (Levels *levels,
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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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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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/* determine input intensity */
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if (levels->high_input[j] != levels->low_input[j])
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{
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inten = ((gdouble) (255.0 * inten - levels->low_input[j]) /
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(gdouble) (levels->high_input[j] - levels->low_input[j]));
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}
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else
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{
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inten = (gdouble) (255.0 * inten - levels->low_input[j]);
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}
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/* clamp to new black and white points */
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inten = CLAMP (inten, 0.0, 1.0);
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if (levels->gamma[j] != 0.0)
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{
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inten = pow ( inten, (1.0 / levels->gamma[j]));
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}
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/* determine the output intensity */
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if (levels->high_output[j] >= levels->low_output[j])
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inten = (gdouble) (inten * (levels->high_output[j] -
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levels->low_output[j]) +
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levels->low_output[j]);
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else if (levels->high_output[j] < levels->low_output[j])
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inten = (gdouble) (levels->low_output[j] - inten *
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(levels->low_output[j] - levels->high_output[j]));
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inten /= 255.0;
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}
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return inten;
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}
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