tracker-extract: add faster PNG extractor

This extractor reads metadata properties from the tEXt and iTXt sections of PNG
files, and skips IDAT sections (this is where the increased speed comes from)

configure.ac

@@ -2186,6 +2186,25 @@ if test "x$enable_guarantee_metadata" != "xno"; then
   AC_DEFINE(GUARANTEE_METADATA, 1, [Guarantee existence of certain metadata])
 fi
 
+#####################################################################
+# Check for tracker-extract: Faster PNG extractor
+#####################################################################
+
+# Extracts metadata from tEXt and iTXt chunks found before and after IDAT
+# chunks Faster than tracker-extract-png since IDAT chunks are skipped.
+
+AC_ARG_ENABLE(png-faster,
+             AS_HELP_STRING([--enable-png-faster],
+                            [enable a faster PNG extractor [[default=no]]]),
+                            [enable_png_faster=yes],
+                            [enable_png_faster=no])
+
+if test "x$enable_png_faster" != "xno"; then
+  AC_DEFINE(HAVE_PNG_FASTER, 1, [Faster PNG extractor])
+fi
+
+AM_CONDITIONAL(HAVE_PNG_FASTER, test "x$enable_png_faster" = "xyes")
+
 ####################################################################
 # Check if we should use initctl or sysvinit
 ####################################################################
@@ -2391,6 +2410,7 @@ Metadata Extractors:
 
 	Support libstreamanalyzer:              $have_libstreamanalyzer
 	Support PNG:                            yes
+	Support faster PNG extraction:          $enable_png_faster
 	Support PDF:                            $have_poppler
 	Support XPS:                            $have_libgxps
 	Support GIF:                            $have_libgif (xmp: $have_exempi)

src/tracker-extract/09-png-faster.rule.in

@@ -0,0 +1,4 @@
+[ExtractorRule]
+ModulePath=@modulesdir@/libextract-png-faster.so
+MimeTypes=image/png
+

src/tracker-extract/Makefile.am

@@ -17,6 +17,7 @@ AM_CPPFLAGS = \
 # duplicates work and requires more maintenance to keep modules up to
 # date.
 rules_in_files = \
+	09-png-faster.rule.in \
 	10-abw.rule.in \
 	10-dvi.rule.in \
 	10-epub.rule.in \
@@ -156,6 +157,11 @@ modules_LTLIBRARIES += libextract-iso.la
 rules_DATA += 11-iso.rule
 endif
 
+if HAVE_PNG_FASTER
+modules_LTLIBRARIES += libextract-png-faster.la
+rules_DATA += 09-png-faster.rule
+endif
+
 # ABW
 libextract_abw_la_SOURCES = tracker-extract-abw.c
 libextract_abw_la_CFLAGS = $(TRACKER_EXTRACT_MODULES_CFLAGS)
@@ -247,6 +253,17 @@ libextract_png_la_LIBADD = \
 	$(TRACKER_EXTRACT_MODULES_LIBS) \
 	$(LIBPNG_LIBS)
 
+# PNG
+libextract_png_faster_la_SOURCES = tracker-extract-png-faster.c
+libextract_png_faster_la_CFLAGS = \
+	$(TRACKER_EXTRACT_MODULES_CFLAGS) \
+	$(LIBPNG_CFLAGS)
+libextract_png_faster_la_LDFLAGS = $(module_flags)
+libextract_png_faster_la_LIBADD = \
+	$(top_builddir)/src/libtracker-extract/libtracker-extract-@TRACKER_API_VERSION@.la \
+	$(top_builddir)/src/libtracker-common/libtracker-common.la \
+	$(BUILD_LIBS) \
+	$(TRACKER_EXTRACT_MODULES_LIBS)
 
 # PS
 libextract_ps_la_SOURCES = tracker-extract-ps.c