Merge pull request #12192 from pasbi:pfm

* created new decoder and encoder for PFM

pfm file format stores binary RGB or grayscale float images.

* added test for pfm codec

* replaced large with short licence header

* little/big-endian-check is now compile time

* fixed width/height confusion, improved big/little endian recognition, fixed scaling issue and Improved signature check

* adapted tests to handle float images well

* removed data-dependency: lena.pfm

the lena image is now loaded is pam and converted to pfm.

* fixed bug in endianess detection macro

* Added endianess detection for android and win

* removed fancy endianess detection

endianess detection will be implemented in cmake scripts soonish.

* fixed minor warnings

* fixed stupid elif defined bug

* silenced some implicit cast warnings

* replaced std::to_string with std::stringstream solution

std::to_string variant did not build on android.

* replaced new endianess macros with existing ones

* improved readability

modules/imgcodecs/src/loadsave.cpp

@@ -156,6 +156,10 @@ struct ImageCodecInitializer
         decoders.push_back( makePtr<PAMDecoder>() );
         encoders.push_back( makePtr<PAMEncoder>() );
     #endif
+    #ifdef HAVE_IMGCODEC_PFM
+        decoders.push_back( makePtr<PFMDecoder>() );
+        encoders.push_back( makePtr<PFMEncoder>() );
+    #endif
     #ifdef HAVE_TIFF
         decoders.push_back( makePtr<TiffDecoder>() );
         encoders.push_back( makePtr<TiffEncoder>() );