fix(openexr): modernize dwa compression level setting

Starting with OpenEXR 3.1.3, the preferred API call for setting DWAA/DWAB compression level has changed. We never changed the OIIO side. Luckily, OpenEXR seems to have kept respecting the old API calls we were making (passing as an attribute). But this modernizes the approach, now that we don't have OpenEXR 2.x suppor to maintain. But in the process, we also fixed a bug! Turns out we weren't propagating the compression properly -- if the compression name was plain "dwaa", we ignored any "openexr:dwaCompressionLevel" attribute, effectively. Signed-off-by: Larry Gritz <[email protected]>
AcademySoftwareFoundation · Sep 20, 2024 · 6b3b206 · 6b3b206
1 parent 187cf72
commit 6b3b206
Showing 1 changed file with 20 additions and 7 deletions.
diff --git a/src/openexr.imageio/exroutput.cpp b/src/openexr.imageio/exroutput.cpp
@@ -22,9 +22,6 @@
 #include <OpenEXR/ImfTiledOutputFile.h>
 
 #include "exr_pvt.h"
-#define OPENEXR_CODED_VERSION                                    \
-    (OPENEXR_VERSION_MAJOR * 10000 + OPENEXR_VERSION_MINOR * 100 \
-     + OPENEXR_VERSION_PATCH)
 
 // The way that OpenEXR uses dynamic casting for attributes requires
 // temporarily suspending "hidden" symbol visibility mode.
@@ -734,16 +731,32 @@ OpenEXROutput::spec_to_header(ImageSpec& spec, int subimage,
             || !ispow2(spec.tile_width) || !ispow2(spec.tile_height))) {
         comp = "zip";
     }
-    if (Strutil::istarts_with(comp, "dwa")) {
-        spec.attribute("openexr:dwaCompressionLevel",
-                       qual > 0 ? float(qual) : 45.0f);
-    }
     spec.attribute("compression", comp);
+
+    // Zip and DWA compression have additional ways to set the levels
 #if OPENEXR_CODED_VERSION >= 30103
+    // OpenEXR 3.1.3 and later allow us to pick the uquality level. We've
+    // found that 4 is a great tradeoff between size and speed, so that is our
+    // default.
     if (Strutil::istarts_with(comp, "zip")) {
         header.zipCompressionLevel() = (qual >= 1 && qual <= 9) ? qual : 4;
     }
 #endif
+    if (Strutil::istarts_with(comp, "dwa") && qual > 0) {
+#if OPENEXR_CODED_VERSION >= 30103
+        // OpenEXR 3.1.3 and later have an API for setting the quality level
+        // in the Header object. Older ones do it by setting an attribute, as
+        // below.
+        header.dwaCompressionLevel() = float(qual);
+#endif
+        // We set this attribute even for older openexr, because even if
+        // we set in the header (above), it gets saved as metadata in the
+        // file so that when we re-read it, we know what the compression
+        // level was.
+        spec.attribute("openexr:dwaCompressionLevel", float(qual));
+    } else {
+        spec.erase_attribute("openexr:dwaCompressionLevel");
+    }
 
     // Default to increasingY line order
     if (!spec.find_attribute("openexr:lineOrder"))