Fixes bugs that cause tests in PR #2599 to fail

include/mapnik/hextree.hpp

@@ -408,7 +408,7 @@ private:
     // clip extreme alfa values
     void create_palette_rek(std::vector<rgba> & palette, node * itr) const
     {
-        if (itr->count >= 3)
+        if (itr->count != 0)
         {
             unsigned count = itr->count;
             byte a = byte(itr->alphas/float(count));

include/mapnik/png_io.hpp

@@ -541,7 +541,7 @@ void save_as_png8_oct(T1 & file,
             trees[j].create_palette(pal);
             leftovers = cols[j] - static_cast<unsigned>(pal.size());
             cols[j] = static_cast<unsigned>(pal.size());
-            palette.insert(palette.begin(), pal.begin(), pal.end());
+            palette.insert(palette.end(), pal.begin(), pal.end());
         }
     }
 

tests/python_tests/png_encoding_test.py

@@ -159,6 +159,42 @@ if mapnik.has_png():
         eq_(len(im.tostring('png8:t=0')) == len(im_in.tostring('png8')), True)
         eq_(len(im.tostring('png8:t=0:m=o')) == len(im_in.tostring('png8:m=o')), True)
 
+    def test_9_colors_hextree():
+        expected = './images/support/encoding-opts/png8-9cols.png'
+        im = mapnik.Image.open(expected)
+        t0 = tmp_dir + 'png-encoding-9-colors.result-hextree.png'
+        im.save(t0, 'png8:m=h')
+        eq_(mapnik.Image.open(t0).tostring(),
+            mapnik.Image.open(expected).tostring(),
+            '%s (actual) not == to %s (expected)' % (t0, expected))
+
+    def test_9_colors_octree():
+        expected = './images/support/encoding-opts/png8-9cols.png'
+        im = mapnik.Image.open(expected)
+        t0 = tmp_dir + 'png-encoding-9-colors.result-octree.png'
+        im.save(t0, 'png8:m=o')
+        eq_(mapnik.Image.open(t0).tostring(),
+            mapnik.Image.open(expected).tostring(),
+            '%s (actual) not == to %s (expected)' % (t0, expected))
+
+    def test_17_colors_hextree():
+        expected = './images/support/encoding-opts/png8-17cols.png'
+        im = mapnik.Image.open(expected)
+        t0 = tmp_dir + 'png-encoding-17-colors.result-hextree.png'
+        im.save(t0, 'png8:m=h')
+        eq_(mapnik.Image.open(t0).tostring(),
+            mapnik.Image.open(expected).tostring(),
+            '%s (actual) not == to %s (expected)' % (t0, expected))
+
+    def test_17_colors_octree():
+        expected = './images/support/encoding-opts/png8-17cols.png'
+        im = mapnik.Image.open(expected)
+        t0 = tmp_dir + 'png-encoding-17-colors.result-octree.png'
+        im.save(t0, 'png8:m=o')
+        eq_(mapnik.Image.open(t0).tostring(),
+            mapnik.Image.open(expected).tostring(),
+            '%s (actual) not == to %s (expected)' % (t0, expected))
+
     def test_2px_regression_hextree():
         im = mapnik.Image.open('./images/support/encoding-opts/png8-2px.A.png')
         expected = './images/support/encoding-opts/png8-2px.png'