Remove dependency on png++, use openCV instead.

cmake/modules/Findpng++.cmake

@@ -1,66 +0,0 @@
-# - Try to find png++
-#
-# The following variables are optionally searched for defaults
-#  png++_ROOT_DIR:            Base directory where all png++ components are found
-#
-# The following are set after configuration is done:
-#  png++_FOUND
-#  png++_INCLUDE_DIRS
-#  png++_LIBRARIES
-
-find_package(PNG REQUIRED)
-
-include(FindPackageHandleStandardArgs)
-
-set(png++_ROOT_DIR "" CACHE PATH "Folder contains png++")
-
-find_path(png++_INCLUDE_DIR
-    NAMES
-        png++/color.hpp
-        png++/config.hpp
-        png++/consumer.hpp
-        png++/convert_color_space.hpp
-        png++/end_info.hpp
-        png++/error.hpp
-        png++/ga_pixel.hpp
-        png++/generator.hpp
-        png++/gray_pixel.hpp
-        png++/image.hpp
-        png++/image_info.hpp
-        png++/index_pixel.hpp
-        png++/info.hpp
-        png++/info_base.hpp
-        png++/io_base.hpp
-        png++/packed_pixel.hpp
-        png++/palette.hpp
-        png++/pixel_buffer.hpp
-        png++/pixel_traits.hpp
-        png++/png.hpp
-        png++/reader.hpp
-        png++/require_color_space.hpp
-        png++/rgb_pixel.hpp
-        png++/rgba_pixel.hpp
-        png++/streaming_base.hpp
-        png++/tRNS.hpp
-        png++/types.hpp
-        png++/writer.hpp
-    PATHS
-        ${png++_ROOT_DIR}
-    PATH_SUFFIXES
-        src)
-
-set(png++_INCLUDE_DIRS ${png++_INCLUDE_DIR} ${PNG_INCLUDE_DIRS})
-set(png++_LIBRARY ${PNG_LIBRARIES})
-
-find_package_handle_standard_args(png++ DEFAULT_MSG
-    png++_INCLUDE_DIR)
-
-if(png++_FOUND)
-    set(png++_INCLUDE_DIRS ${png++_INCLUDE_DIR})
-    set(png++_LIBRARIES ${png++_LIBRARY})
-
-    add_library(png++::png++ INTERFACE IMPORTED)
-    set_target_properties(png++::png++ PROPERTIES
-        INTERFACE_INCLUDE_DIRECTORIES ${png++_INCLUDE_DIR}
-        INTERFACE_LINK_LIBRARIES PNG::PNG)
-endif()