1 files changed, 117 insertions, 0 deletions
diff --git a/tools/svg-contrast.c b/tools/svg-contrast.c
new file mode 100644
index 0000000..11cf136
--- /dev/null
+++ b/tools/svg-contrast.c
@@ -0,0 +1,117 @@
+/* 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;
+}