Patch for exact-image to support new libPNG

gistfile1.diff

diff --git a/codecs/png.cc b/codecs/png.cc
index be70a53..65cee67 100644
--- a/codecs/png.cc
+++ b/codecs/png.cc
@@ -23,6 +23,12 @@
 #include "png.hh" #include "Endianess.hh"
+#define png_infopp_NULL (png_infopp)NULL
+#define int_p_NULL (int*)NULL
+#define png_bytepp_NULL (png_bytepp)NULL
+#define Z_BEST_COMPRESSION 100
+
+
 void stdstream_read_data(png_structp png_ptr,
                         png_bytep data, png_size_t length)
 {
@@ -104,7 +110,8 @@ int PNGCodec::readImage (std::istream* stream, Image&
image, const std::string&
   image.w = width;
   image.h = height;
   image.bps = bit_depth;
-  image.spp = info_ptr->channels;
+//  image.spp = info_ptr->channels;
+  image.spp = png_get_channels(png_ptr, info_ptr);

   png_uint_32 res_x, res_y;
   res_x = png_get_x_pixels_per_meter(png_ptr, info_ptr);
@@ -123,7 +130,13 @@ int PNGCodec::readImage (std::istream* stream, Image&
image, const std::string&
   if (color_type == PNG_COLOR_TYPE_PALETTE) {
     png_set_palette_to_rgb(png_ptr);
     image.bps = 8;
-    if (info_ptr->num_trans)
+
+    png_bytep trans_alpha;
+    int num_trans;
+    png_color_16p trans_color;
+    png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
+                         &num_trans, &trans_color);
+    if (num_trans)
       image.spp = 4;
     else
       image.spp = 3;
@@ -244,7 +257,7 @@ bool PNGCodec::writeImage (std::ostream* stream, Image&
image, int quality,
   else if (quality > Z_BEST_COMPRESSION) quality = Z_BEST_COMPRESSION;
   png_set_compression_level(png_ptr, quality);

-  png_info_init (info_ptr);
+  //png_info_init (info_ptr);

   /* Set up our STL stream output control */
   png_set_write_fn (png_ptr, stream, &stdstream_write_data,
&stdstream_flush_data);