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diff --git a/src/png/pixel_traits.hpp b/src/png/pixel_traits.hpp
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+/*
+ * Copyright (C) 2007,2008   Alex Shulgin
+ *
+ * This file is part of png++ the C++ wrapper for libpng.  PNG++ is free
+ * software; the exact copying conditions are as follows:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
+ * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef PNGPP_PIXEL_TRAITS_HPP_INCLUDED
+#define PNGPP_PIXEL_TRAITS_HPP_INCLUDED
+
+#include <limits>
+#include "types.hpp"
+
+namespace png
+{
+
+    /**
+     * \brief Pixel traits class template.
+     *
+     * Provides information about pixel color type and components bit depth.
+     * Not implemented--see specializations.
+     *
+     * \see  pixel_traits<rgb_pixel>, pixel_traits<rgba_pixel>
+     */
+    template< typename pixel > struct pixel_traits;
+
+    /**
+     * \brief Basic pixel traits class template.
+     *
+     * Provides common implementation for various pixel_traits<>
+     * specializations.
+     */
+    template< typename pixel,
+              typename component,
+              color_type pixel_color_type,
+              int channels_value = sizeof(pixel) / sizeof(component),
+              int bit_depth_value = std::numeric_limits< component >::digits >
+    struct basic_pixel_traits
+    {
+        typedef pixel pixel_type;
+        typedef component component_type;
+
+        static color_type get_color_type()
+        {
+            return pixel_color_type;
+        }
+        
+        static const int channels = channels_value;
+        static int get_channels()
+        {
+            return channels;
+        }
+        
+        static const int bit_depth = bit_depth_value;
+        static int get_bit_depth()
+        {
+            return bit_depth;
+        }
+    };
+
+    /**
+     * \brief Basic pixel traits class template for pixels with alpha
+     * channel.
+     */
+    template< typename component >
+    struct basic_alpha_pixel_traits
+    {
+        /**
+         * \brief Returns the default alpha channel filler for full
+         * opacity.
+         */
+        static component get_alpha_filler()
+        {
+            return std::numeric_limits< component >::max();
+        }
+    };
+
+} // namespace png
+
+#endif // PNGPP_PIXEL_TRAITS_HPP_INCLUDED