imgcodecs: ensure parameters are key-value pairs, fix HDR encoder

modules/imgcodecs/include/opencv2/imgcodecs.hpp

@@ -96,6 +96,7 @@ enum ImwriteFlags {
        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_HDR_COMPRESSION     = (5 << 4) + 0, /* 80 */ //!< specify HDR compression
        IMWRITE_PAM_TUPLETYPE       = 128,//!< For PAM, sets the TUPLETYPE field to the corresponding string value that is defined for the format
        IMWRITE_TIFF_RESUNIT        = 256,//!< For TIFF, use to specify which DPI resolution unit to set; see libtiff documentation for valid values.
        IMWRITE_TIFF_XDPI           = 257,//!< For TIFF, use to specify the X direction DPI.
@@ -145,6 +146,12 @@ enum ImwritePAMFlags {
        IMWRITE_PAM_FORMAT_RGB_ALPHA       = 5
      };
 
+//! Imwrite HDR specific values for IMWRITE_HDR_COMPRESSION parameter key
+enum ImwriteHDRCompressionFlags {
+    IMWRITE_HDR_COMPRESSION_NONE = 0,
+    IMWRITE_HDR_COMPRESSION_RLE = 1
+};
+
 //! @} imgcodecs_flags
 
 /** @brief Loads an image from a file.