Add zstd as a compression option for the OpenEXR plugin in OIIO

src/doc/builtinplugins.rst

@@ -1543,16 +1543,17 @@ The official OpenEXR site is http://www.openexr.com/.
    * - ``compression``
      - string
      - one of: ``"none"``, ``"rle"``, ``"zip"``, ``"zips"``, ``"piz"``,
-       ``"pxr24"``, ``"b44"``, ``"b44a"``, ``"dwaa"``, ``"dwab"`` or ``"htj2k"``.
+       ``"pxr24"``, ``"b44"``, ``"b44a"``, ``"dwaa"``, ``"dwab"``, ``"htj2k"`` or ``"zstd"``.
        (``"htj2k"`` is only supported with OpenEXR 3.4 or later.)
+       (``"zstd"`` is only supported with OpenEXR 3.5 or later.)
        If the writer receives a request for a compression type it does not
        recognize or is not supported by the version of OpenEXR on the
        system, it will use ``"zip"`` by default. For ``"dwaa"`` and
        ``"dwab"``, the dwaCompressionLevel may be optionally appended to the
        compression name after a colon, like this: ``"dwaa:200"``. (The
-       default DWA compression value is 45.) For ``"zip"`` and ``"zips"``
+       default DWA compression value is 45.) For ``"zip"``, ``"zips"`` and ``"zstd"``
        compression, a level from 1 to 9 may be appended (the default is
-       ``"zip:4"``), but note that this is only honored when building
+       ``"zip:4"`` and ``"zstd:5"``), but note that this is only honored when building
        against OpenEXR 3.1.3 or later.
    * - ``textureformat``
      - string

src/openexr.imageio/exrinput.cpp

@@ -433,6 +433,9 @@ OpenEXRInput::PartInfo::parse_header(OpenEXRInput* in,
         case Imf::DWAB_COMPRESSION: comp = "dwab"; break;
 #ifdef IMF_HTJ2K_COMPRESSION
         case Imf::HTJ2K_COMPRESSION: comp = "htj2k"; break;
+#endif
+#ifdef IMF_ZSTD_COMPRESSION
+        case Imf::ZSTD_COMPRESSION: comp = "zstd"; break;
 #endif
         default: break;
         }

src/openexr.imageio/exrinput_c.cpp

@@ -570,6 +570,9 @@ OpenEXRCoreInput::PartInfo::parse_header(OpenEXRCoreInput* in,
         case EXR_COMPRESSION_DWAB: comp = "dwab"; break;
 #ifdef IMF_HTJ2K_COMPRESSION
         case EXR_COMPRESSION_HTJ2K: comp = "htj2k"; break;
+#endif
+#ifdef IMF_ZSTD_COMPRESSION
+        case EXR_COMPRESSION_ZSTD: comp = "zstd"; break;
 #endif
         default: break;
         }

src/openexr.imageio/exroutput.cpp

@@ -742,6 +742,14 @@ OpenEXROutput::spec_to_header(ImageSpec& spec, int subimage,
     if (Strutil::istarts_with(comp, "zip")) {
         header.zipCompressionLevel() = (qual >= 1 && qual <= 9) ? qual : 4;
     }
+#endif
+#if OPENEXR_CODED_VERSION >= 30500
+    // OpenEXR 3.5.0 and later allow us to pick the level. We've found
+    // that 5 is a great tradeoff between size and speed, so that is our
+    // default.
+    if (Strutil::istarts_with(comp, "zstd")) {
+        header.zstdCompressionLevel() = (qual >= 1 && qual <= 9) ? qual : 5;
+    }
 #endif
     if (Strutil::istarts_with(comp, "dwa") && qual > 0) {
 #if OPENEXR_CODED_VERSION >= 30103
@@ -964,6 +972,10 @@ OpenEXROutput::put_parameter(const std::string& name, TypeDesc type,
 #ifdef IMF_HTJ2K_COMPRESSION
             else if (Strutil::iequals(str, "htj2k"))
                 header.compression() = Imf::HTJ2K_COMPRESSION;
+#endif
+#ifdef IMF_ZSTD_COMPRESSION
+            else if (Strutil::iequals(str, "zstd"))
+                header.compression() = Imf::ZSTD_COMPRESSION;
 #endif
         }
         return true;