gimp/app/base/levels.c

115 lines
3.1 KiB
C

/* GIMP - The GNU Image Manipulation Program
* Copyright (C) 1995 Spencer Kimball and Peter Mattis
*
* 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 3 of the License, or
* (at your option) any later version.
*
* 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, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <glib-object.h>
#include "libgimpmath/gimpmath.h"
#include "libgimpcolor/gimpcolortypes.h"
#include "libgimpcolor/gimprgb.h"
#include "base-types.h"
#include "levels.h"
/* public functions */
void
levels_init (Levels *levels)
{
GimpHistogramChannel channel;
g_return_if_fail (levels != NULL);
for (channel = GIMP_HISTOGRAM_VALUE;
channel <= GIMP_HISTOGRAM_ALPHA;
channel++)
{
levels->gamma[channel] = 1.0;
levels->low_input[channel] = 0;
levels->high_input[channel] = 255;
levels->low_output[channel] = 0;
levels->high_output[channel] = 255;
}
}
gfloat
levels_lut_func (Levels *levels,
gint n_channels,
gint channel,
gfloat value)
{
gdouble inten;
gint j;
if (n_channels <= 2)
j = channel;
else
j = channel + 1;
inten = value;
/* For RGB and RGBA images this runs through the loop with j = channel + 1
* the first time and j = 0 the second time
*
* For GRAY images this runs through the loop with j = 0 the first and
* only time
*/
for (; j >= 0; j -= (channel + 1))
{
/* don't apply the overall curve to the alpha channel */
if (j == 0 && (n_channels == 2 || n_channels == 4) &&
channel == n_channels - 1)
return inten;
/* determine input intensity */
if (levels->high_input[j] != levels->low_input[j])
{
inten = ((gdouble) (255.0 * inten - levels->low_input[j]) /
(gdouble) (levels->high_input[j] - levels->low_input[j]));
}
else
{
inten = (gdouble) (255.0 * inten - levels->low_input[j]);
}
/* clamp to new black and white points */
inten = CLAMP (inten, 0.0, 1.0);
if (levels->gamma[j] != 0.0)
{
inten = pow ( inten, (1.0 / levels->gamma[j]));
}
/* determine the output intensity */
if (levels->high_output[j] >= levels->low_output[j])
inten = (gdouble) (inten * (levels->high_output[j] -
levels->low_output[j]) +
levels->low_output[j]);
else if (levels->high_output[j] < levels->low_output[j])
inten = (gdouble) (levels->low_output[j] - inten *
(levels->low_output[j] - levels->high_output[j]));
inten /= 255.0;
}
return inten;
}