Add support for cmake to look for libpng and then add the proper files if available.

IO/CMakeLists.txt

@@ -8,6 +8,15 @@ SET( HEADERS
 	ImageFile.h
 )
 
+FIND_PACKAGE( PNG )
+IF( PNG_FOUND )
+	INCLUDE_DIRECTORIES( ${PNG_INCLUDE_DIR} )
+	TARGET_LINK_LIBRARIES( ${PNG_LIBRARY} )
+
+	SET( SOURCES ${SOURCES} ImageLoaderPNG.cpp )
+	SET( HEADERS ${HEADERS} ImageLoaderPNG.h )
+ENDIF()
+
 CONFIGURE_FILE(
 	"ImageLoader.h.in"
 	"ImageLoader.h"

IO/ImageFile.cpp

@@ -1,5 +1,9 @@
-#include "ImageFile.h"
 #include <string.h>
+#include "ImageFile.h"
+
+#ifdef PNG_FOUND
+#  include "ImageLoaderPNG.h"
+#endif
 
 ImageFile::ImageFile(const char *filename) : 
   m_PixelData(0),

IO/ImageLoader.h.in

@@ -43,4 +43,6 @@ class ImageLoader {
   unsigned char * GetAlphaPixelData() const { return m_AlphaData; }
 };
 
+#cmakedefine PNG_FOUND
+
 #endif // _IMAGE_LOADER_H_

IO/ImageLoaderPNG.cpp

@@ -0,0 +1,14 @@
+#include "ImageLoaderPNG.h"
+
+#include <png.h>
+
+ImageLoaderPNG::ImageLoaderPNG(const unsigned char *rawData) 
+  : ImageLoader(rawData)
+{
+}
+
+ImageLoaderPNG::~ImageLoaderPNG() {
+}
+
+void ImageLoaderPNG::ReadData() {
+}

IO/ImageLoaderPNG.h

@@ -5,10 +5,10 @@
 
 class ImageLoaderPNG : public ImageLoader {
  public:
-  ImageLoader(const unsigned char *rawData);
+  ImageLoaderPNG(const unsigned char *rawData);
-  virtual ~ImageLoader();
+  virtual ~ImageLoaderPNG();
 
-  void ReadData();
+  virtual void ReadData();
 };
 
 #endif // _IMAGE_LOADER_H_