Merge pull request #10283 from zhijackchen:exr_export

* Fix issue #10114
Convert table change
From:
CV_8U -> HALF
CV_8S -> HALF
CV_16U -> UINT
CV_16S -> UINT
CV_32S -> UINT
CV_32F -> FLOAT
To:
CV_8U -> HALF
CV_8S -> HALF
CV_16U -> UINT
CV_16S -> FLOAT
CV_32S -> FLOAT loss precision
CV_32F -> FLOAT
Signed integer can't be presented well with UINT. Even adjust bias, CV16S and CV32S will be confused when load from exr file.
Also fix CV_8S negative value incorrect bug

* EXR import and export
imread() from EXR returns CV_32F only
imwrite() accepts CV_32 cv::Mat only and stores FLOAT images by default. Add imwrite() flag to store in HALF format.

* fix compiling error

* clean up

* fix EXR import issues

modules/imgcodecs/include/opencv2/imgcodecs.hpp

@@ -89,10 +89,17 @@ enum ImwriteFlags {
        IMWRITE_PNG_STRATEGY        = 17, //!< One of cv::ImwritePNGFlags, default is IMWRITE_PNG_STRATEGY_RLE.
        IMWRITE_PNG_BILEVEL         = 18, //!< Binary level PNG, 0 or 1, default is 0.
        IMWRITE_PXM_BINARY          = 32, //!< For PPM, PGM, or PBM, it can be a binary format flag, 0 or 1. Default value is 1.
+       IMWRITE_EXR_TYPE            = (3 << 4) + 0, /* 48 */ //!< override EXR storage type (FLOAT (FP32) is default)
        IMWRITE_WEBP_QUALITY        = 64, //!< For WEBP, it can be a quality from 1 to 100 (the higher is the better). By default (without any parameter) and for quality above 100 the lossless compression is used.
        IMWRITE_PAM_TUPLETYPE       = 128,//!< For PAM, sets the TUPLETYPE field to the corresponding string value that is defined for the format
      };
 
+enum ImwriteEXRTypeFlags {
+       /*IMWRITE_EXR_TYPE_UNIT = 0, //!< not supported */
+       IMWRITE_EXR_TYPE_HALF = 1,   //!< store as HALF (FP16)
+       IMWRITE_EXR_TYPE_FLOAT = 2   //!< store as FP32 (default)
+     };
+
 //! Imwrite PNG specific flags used to tune the compression algorithm.
 /** These flags will be modify the way of PNG image compression and will be passed to the underlying zlib processing stage.
 

modules/imgcodecs/include/opencv2/imgcodecs/imgcodecs_c.h

@@ -94,6 +94,7 @@ enum
     CV_IMWRITE_PNG_STRATEGY_RLE =3,
     CV_IMWRITE_PNG_STRATEGY_FIXED =4,
     CV_IMWRITE_PXM_BINARY =32,
+    CV_IMWRITE_EXR_TYPE = 48,
     CV_IMWRITE_WEBP_QUALITY =64,
     CV_IMWRITE_PAM_TUPLETYPE = 128,
     CV_IMWRITE_PAM_FORMAT_NULL = 0,