[gimp] tools: "invert-svg", new tool to invert grey colors in vectorial icons.

[Jehan Pagès <jehanp src gnome org>]

commit 1427b2c7954ae95c44a9a71df61f06c352633b15
Author: Jehan <jehan girinstud io>
Date:   Sun Feb 14 00:01:20 2016 +0100

    tools: "invert-svg", new tool to invert grey colors in vectorial icons.

 tools/Makefile.am  |   14 ++++++-
 tools/invert-svg.c |  107 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+), 1 deletions(-)
---
diff --git a/tools/Makefile.am b/tools/Makefile.am
index 7ca1d2c..a6c8617 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -2,6 +2,10 @@
 
 libgimpbase = $(top_builddir)/libgimpbase/libgimpbase-$(GIMP_API_VERSION).la
 
+if ENABLE_VECTOR_ICONS
+invert_svg = invert-svg
+endif
+
 if WITH_PDBGEN
 D_pdbgen = pdbgen
 else
@@ -24,7 +28,7 @@ bin_PROGRAMS = gimptool-2.0
 
 endif
 
-noinst_PROGRAMS = test-clipboard
+noinst_PROGRAMS = test-clipboard $(invert_svg)
 
 EXTRA_PROGRAMS = \
        kernelgen
@@ -43,6 +47,14 @@ test_clipboard_SOURCES = test-clipboard.c
 test_clipboard_LDADD = \
        $(GTK_LIBS)
 
+if ENABLE_VECTOR_ICONS
+invert_svg_SOURCES = invert-svg.c
+
+invert_svg_LDADD = \
+       $(GLIB_LIBS)    \
+       $(GIO_LIBS)
+endif
+
 AM_CPPFLAGS = \
        -DGIMP_APP_VERSION=\"@GIMP_APP_VERSION \"               \
        -DLOCALEDIR=\""$(gimplocaledir)"\"                      \
diff --git a/tools/invert-svg.c b/tools/invert-svg.c
new file mode 100644
index 0000000..9282d15
--- /dev/null
+++ b/tools/invert-svg.c
@@ -0,0 +1,107 @@
+/* invert-svg-grey.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 <http://www.gnu.org/licenses/>.
+ */
+
+#include <gio/gio.h>
+#include <glib/gprintf.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
+invert_rgb_color (const GMatchInfo *info,
+                  GString          *res,
+                  gpointer          data)
+{
+  gchar *match;
+  gchar *inverted;
+  gint   value;
+
+  /* We only invert grey colors, so we just need the first channel. */
+  match = g_match_info_fetch (info, 1);
+  value = strtol (match, NULL, 16);
+  value = 255 - value;
+  inverted = g_strdup_printf ("#%02x%02x%02x",
+                              value, value, value);
+
+  g_string_append (res, inverted);
+  g_free (inverted);
+  g_free (match);
+
+  return FALSE;
+}
+
+int main (int argc, char **argv)
+{
+  gchar  *input;
+  gchar  *output;
+  GFile  *file;
+  gchar  *contents;
+  gchar  *replaced;
+  GRegex *regex;
+  gint    retval = 0;
+
+  if (argc != 3)
+    {
+      g_fprintf (stderr, "Usage: invert-svg svg-image inverted-svg-output\n");
+      return 1;
+    }
+  input  = argv[1];
+  output = argv[2];
+
+  file = g_file_new_for_path (input);
+  if (! g_file_load_contents (file, NULL, &contents, NULL, NULL, NULL))
+    {
+      g_fprintf (stderr,
+                 "Error: invert-svg 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,
+                                   invert_rgb_color, NULL, 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: invert-svg 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;
+}