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/* svg-contrast.c
* Copyright (C) 2016 Jehan
*
* 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 <https://www.gnu.org/licenses/>.
*/
#include <gio/gio.h>
#include <glib/gprintf.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
/* This tool inverts grey colors in a SVG image.
* Non-grey colors are not touched, since they are considered
* exceptions that we would want to keep the same (for instance
* Red, Blue or Green channel representations).
*
* It is not based off XML knowledge since colors could appear in
* various fields. Instead we just assume that a color has the XML
* format "#RRGGBB" and we use regular expression to update these.
*/
static gboolean
rgb_color_contrast (const GMatchInfo *info,
GString *res,
gpointer data)
{
gchar *match;
gchar *adjusted;
gdouble contrast;
gdouble value;
gint value_u8;
contrast = *(const gdouble *) data;
/* We only adjust grey colors, so we just need the first channel. */
match = g_match_info_fetch (info, 1);
value_u8 = strtol (match, NULL, 16);
value = value_u8 / 255.0;
value = 0.5 + contrast * (value - 0.5);
value = CLAMP (value, 0.0, 1.0);
value_u8 = floor (255.0 * value + 0.5);
adjusted = g_strdup_printf ("#%02x%02x%02x",
value_u8, value_u8, value_u8);
g_string_append (res, adjusted);
g_free (adjusted);
g_free (match);
return FALSE;
}
int main (int argc, char **argv)
{
gchar *input;
gchar *output;
gdouble contrast;
GFile *file;
gchar *contents;
gchar *replaced;
GRegex *regex;
gint retval = 0;
if (argc != 4)
{
g_fprintf (stderr, "Usage: svg-contrast input output [contrast]\n");
return 1;
}
input = argv[1];
output = argv[2];
contrast = atof (argv[3]);
file = g_file_new_for_path (input);
if (! g_file_load_contents (file, NULL, &contents, NULL, NULL, NULL))
{
g_fprintf (stderr,
"Error: svg-contrast could not load contents of file %s.\n",
input);
g_object_unref (file);
return 1;
}
g_object_unref (file);
/* Replace grey colors only. */
regex = g_regex_new ("#([0-9a-fA-F]{2}){3}\\b", 0, 0, NULL);
replaced = g_regex_replace_eval (regex, contents, -1, 0, 0,
rgb_color_contrast, &contrast, NULL);
file = g_file_new_for_path (output);
if (! g_file_replace_contents (file, replaced, strlen (replaced),
NULL, FALSE,
G_FILE_CREATE_REPLACE_DESTINATION,
NULL, NULL, NULL))
{
g_fprintf (stderr,
"Error: svg-contrast could not save file %s.\n",
output);
retval = 1;
}
g_object_unref (file);
g_free (contents);
g_free (replaced);
g_regex_unref (regex);
return retval;
}
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