use original pHash source code & extract patch to support alpha chann…

…el PNGs

fix PR#20 => westonplatter#23

.gitignore

@@ -28,4 +28,5 @@ ext/phashion_ext
 !ext/phashion_ext/extconf.rb
 !ext/phashion_ext/phashion_ext.c
 !ext/phashion_ext/pHash-0.9.6.tar.gz
+!ext/phashion_ext/patches
 lib/phashion_ext.bundle

ext/phashion_ext/extconf.rb

@@ -1,4 +1,5 @@
 require 'mkmf'
+require 'fileutils'
 
 BASEDIR     = File.expand_path(File.dirname(__FILE__))
 BUNDLE      = Dir.glob("#{BASEDIR}/pHash-*.tar.gz").first
@@ -19,6 +20,10 @@
     puts(cmd = "tar xzf #{BUNDLE} 2>&1")
     raise "'#{cmd}' failed" unless system(cmd)
 
+    puts "patching pHash sources for PNG alpha channel support"
+    puts(cmd = "patch -d pHash-0.9.6 -p1 < #{File.join 'patches', 'png_alpha.diff'}")
+    raise "'#{cmd}' failed" unless system(cmd)
+
     Dir.chdir(BUNDLE_PATH) do
       puts(cmd = "env CXXFLAGS='#{$CXXFLAGS}' CFLAGS='#{$CFLAGS}' LDFLAGS='#{$LDFLAGS}' ./configure --prefix=#{BASEDIR} --disable-audio-hash --disable-video-hash --disable-shared --with-pic 2>&1")
       raise "'#{cmd}' failed" unless system(cmd)

ext/phashion_ext/patches/png_alpha.diff

@@ -0,0 +1,16 @@
+--- pHash-0.9.6-orig/src/pHash.cpp	2013-04-13 19:23:12.000000000 +0200
++++ pHash-0.9.6-mod/src/pHash.cpp	2013-11-25 02:53:36.000000000 +0100
+@@ -369,10 +369,9 @@
+     if (src.spectrum() == 3){
+         img = src.RGBtoYCbCr().channel(0).get_convolve(meanfilter);
+     } else if (src.spectrum() == 4){
+-	int width = img.width();
+-        int height = img.height();
+-        int depth = img.depth();
+-	img = src.crop(0,0,0,0,width-1,height-1,depth-1,2).RGBtoYCbCr().channel(0).get_convolve(meanfilter);
++       int width  = src.width();
++       int height = src.height();
++       img = src.crop(0,0,0,0,width-1,height-1,0,2).RGBtoYCbCr().channel(0).get_convolve(meanfilter);
+     } else {
+ 	img = src.channel(0).get_convolve(meanfilter);
+     }