feat(exr): Write OpenEXR colorInteropID metadata based on oiio:ColorSpace

If the colorspace exists and has an interop ID in an OCIO 2.5 config, use that.
Otherwise check if the colorspace is equivalent to a known color interop ID.

Adds a new get_color_interop_id(colorspace) API function.

Signed-off-by: Brecht Van Lommel <[email protected]>

Author: brechtvl

src/include/OpenImageIO/color.h

@@ -408,6 +408,12 @@ class OIIO_API ColorConfig {
     /// @version 3.1
     cspan<int> get_cicp(string_view colorspace) const;
 
+    /// Find color interop ID for the given colorspace.
+    /// Returns empty string if not found.
+    ///
+    /// @version 3.1
+    string_view get_color_interop_id(string_view colorspace) const;
+
     /// Find color interop ID corresponding to the CICP code.
     /// Returns empty string if not found.
     ///

src/libOpenImageIO/color_ocio.cpp

@@ -2033,38 +2033,56 @@ enum class CICPRange : int {
 };
 
 struct ColorInteropID {
+    constexpr ColorInteropID(const char* interop_id)
+        : interop_id(interop_id)
+        , cicp({ 0, 0, 0, 0 })
+        , have_cicp(false)
+    {
+    }
+
     constexpr ColorInteropID(const char* interop_id, CICPPrimaries primaries,
                              CICPTransfer transfer, CICPMatrix matrix)
         : interop_id(interop_id)
         , cicp({ int(primaries), int(transfer), int(matrix),
                  int(CICPRange::Full) })
+        , have_cicp(true)
     {
     }
 
     const char* interop_id;
     std::array<int, 4> cicp;
+    bool have_cicp;
 };
 
 // Mapping between color interop ID and CICP, based on Color Interop Forum
 // recommendations.
 constexpr ColorInteropID color_interop_ids[] = {
     // Scene referred interop IDs first so they are the default in automatic
-    // conversion from CICP to interop ID.
-    { "srgb_rec709_scene", CICPPrimaries::Rec709, CICPTransfer::sRGB,
-      CICPMatrix::BT709 },
-    { "srgb_p3d65_scene", CICPPrimaries::P3D65, CICPTransfer::sRGB,
-      CICPMatrix::BT709 },
-    { "g22_rec709_scene", CICPPrimaries::Rec709, CICPTransfer::Gamma22,
-      CICPMatrix::BT709 },
-    // These are not display color spaces at all, but can be represented by CICP.
+    // conversion from CICP to interop ID. Some are not display color spaces
+    // at all, but can be represented by CICP anyway.
+    { "lin_ap1_scene" },
+    { "lin_ap0_scene" },
     { "lin_rec709_scene", CICPPrimaries::Rec709, CICPTransfer::Linear,
       CICPMatrix::BT709 },
     { "lin_p3d65_scene", CICPPrimaries::P3D65, CICPTransfer::Linear,
       CICPMatrix::BT709 },
     { "lin_rec2020_scene", CICPPrimaries::Rec2020, CICPTransfer::Linear,
       CICPMatrix::Rec2020_CL },
+    { "lin_adobergb_scene" },
     { "lin_ciexyzd65_scene", CICPPrimaries::XYZD65, CICPTransfer::Linear,
       CICPMatrix::Unspecified },
+    { "srgb_rec709_scene", CICPPrimaries::Rec709, CICPTransfer::sRGB,
+      CICPMatrix::BT709 },
+    { "g22_rec709_scene", CICPPrimaries::Rec709, CICPTransfer::Gamma22,
+      CICPMatrix::BT709 },
+    { "g18_rec709_scene" },
+    { "srgb_ap1_scene" },
+    { "g22_ap1_scene" },
+    { "srgb_p3d65_scene", CICPPrimaries::P3D65, CICPTransfer::sRGB,
+      CICPMatrix::BT709 },
+    { "g22_adobergb_scene" },
+    { "data" },
+    { "unknown" },
 
     // Display referred interop IDs.
     { "srgb_rec709_display", CICPPrimaries::Rec709, CICPTransfer::sRGB,
@@ -2084,7 +2102,7 @@ constexpr ColorInteropID color_interop_ids[] = {
     { "g22_rec709_display", CICPPrimaries::Rec709, CICPTransfer::Gamma22,
       CICPMatrix::BT709 },
     // No CICP code for Adobe RGB primaries.
-    // { "g22_adobergb_display" }
+    { "g22_adobergb_display" },
     { "g26_p3d65_display", CICPPrimaries::P3D65, CICPTransfer::Gamma26,
       CICPMatrix::BT709 },
     { "g26_xyzd65_display", CICPPrimaries::XYZD65, CICPTransfer::Gamma26,
@@ -2094,11 +2112,35 @@ constexpr ColorInteropID color_interop_ids[] = {
 };
 }  // namespace
 
+string_view
+ColorConfig::get_color_interop_id(string_view colorspace) const
+{
+    if (colorspace.empty())
+        return "";
+#if OCIO_VERSION_HEX >= MAKE_OCIO_VERSION_HEX(2, 5, 0)
+    if (getImpl()->config_ && !disable_ocio) {
+        OCIO::ConstColorSpaceRcPtr c = getImpl()->config_->getColorSpace(
+            std::string(resolve(colorspace)).c_str());
+        const char* interop_id = (c) ? c->getInteropID() : nullptr;
+        if (interop_id) {
+            return interop_id;
+        }
+    }
+#endif
+    for (const ColorInteropID& interop : color_interop_ids) {
+        if (equivalent(colorspace, interop.interop_id)) {
+            return interop.interop_id;
+        }
+    }
+    return "";
+}
+
 string_view
 ColorConfig::get_color_interop_id(const int cicp[4]) const
 {
     for (const ColorInteropID& interop : color_interop_ids) {
-        if (interop.cicp[0] == cicp[0] && interop.cicp[1] == cicp[1]) {
+        if (interop.have_cicp && interop.cicp[0] == cicp[0]
+            && interop.cicp[1] == cicp[1]) {
             return interop.interop_id;
         }
     }
@@ -2110,7 +2152,8 @@ ColorConfig::get_cicp(string_view colorspace) const
 {
     if (!colorspace.empty()) {
         for (const ColorInteropID& interop : color_interop_ids) {
-            if (equivalent(colorspace, interop.interop_id)) {
+            if (interop.have_cicp
+                && equivalent(colorspace, interop.interop_id)) {
                 return interop.cicp;
             }
         }

src/openexr.imageio/exroutput.cpp

@@ -13,6 +13,7 @@
 #include <numeric>
 
 #include <OpenImageIO/Imath.h>
+#include <OpenImageIO/color.h>
 #include <OpenImageIO/platform.h>
 
 #include <OpenEXR/IlmThreadPool.h>
@@ -1026,6 +1027,15 @@ OpenEXROutput::spec_to_header(ImageSpec& spec, int subimage,
         }
     }
 
+    // Set color interop ID from colorspace
+    if (spec.get_string_attribute("colorInteropID").empty()) {
+        const ColorConfig& colorconfig(ColorConfig::default_colorconfig());
+        string_view colorspace = spec.get_string_attribute("oiio:ColorSpace");
+        string_view interop_id = colorconfig.get_color_interop_id(colorspace);
+        if (!interop_id.empty())
+            spec.attribute("colorInteropID", interop_id);
+    }
+
     // Deal with all other params
     for (const auto& p : spec.extra_attribs)
         put_parameter(p.name().string(), p.type(), p.data(), header);

src/python/py_colorconfig.cpp

@@ -161,6 +161,10 @@ declare_colorconfig(py::module& m)
                 return self.equivalent(color_space, other_color_space);
             },
             "color_space"_a, "other_color_space"_a)
+        .def("get_color_interop_id",
+             [](const ColorConfig& self, const std::string& colorspace) {
+                 return std::string(self.get_color_interop_id(colorspace));
+             })
         .def("get_color_interop_id",
              [](const ColorConfig& self, const std::array<int, 4> cicp) {
                  return std::string(self.get_color_interop_id(cicp.data()));

testsuite/openexr-suite/ref/out.txt

@@ -369,3 +369,37 @@ Full command line was:
 oiiotool ERROR: -o : Cannot output non-compliant ACES Container in 'strict' mode. REASON: EXR data type is not 'HALF' as required for an ACES Container.
 Full command line was:
 > oiiotool --create 4x4 3 -d float --compression none -sattrib openexr:ACESContainerPolicy strict -o strict-fail.exr
+Reading color_interop_id_scene_linear.exr
+color_interop_id_scene_linear.exr :    4 x    4, 3 channel, float openexr
+    SHA-1: D7699308C38CD04EEB732577A82D31D04E05A339
+    channel list: R, G, B
+    colorInteropID: "lin_ap1_scene"
+    compression: "zip"
+    PixelAspectRatio: 1
+    screenWindowCenter: 0, 0
+    screenWindowWidth: 1
+    oiio:ColorSpace: "lin_ap1_scene"
+    oiio:subimages: 1
+    openexr:lineOrder: "increasingY"
+Reading color_interop_id_linear_adobergb.exr
+color_interop_id_linear_adobergb.exr :    4 x    4, 3 channel, float openexr
+    SHA-1: D7699308C38CD04EEB732577A82D31D04E05A339
+    channel list: R, G, B
+    colorInteropID: "lin_adobergb_scene"
+    compression: "zip"
+    PixelAspectRatio: 1
+    screenWindowCenter: 0, 0
+    screenWindowWidth: 1
+    oiio:ColorSpace: "lin_adobergb_scene"
+    oiio:subimages: 1
+    openexr:lineOrder: "increasingY"
+Reading color_interop_id_unknown.exr
+color_interop_id_unknown.exr :    4 x    4, 3 channel, float openexr
+    SHA-1: D7699308C38CD04EEB732577A82D31D04E05A339
+    channel list: R, G, B
+    compression: "zip"
+    PixelAspectRatio: 1
+    screenWindowCenter: 0, 0
+    screenWindowWidth: 1
+    oiio:subimages: 1
+    openexr:lineOrder: "increasingY"

testsuite/openexr-suite/run.py

@@ -83,3 +83,11 @@
 
 # Invalid data type
 command += oiiotool("--create 4x4 3 -d float --compression none -sattrib openexr:ACESContainerPolicy strict -o strict-fail.exr", failureok=True)
+
+# Check color interop ID output
+command += oiiotool("--create 4x4 3 --attrib oiio:ColorSpace scene_linear -o color_interop_id_scene_linear.exr")
+command += info_command("color_interop_id_scene_linear.exr", safematch=True)
+command += oiiotool("--create 4x4 3 --attrib oiio:ColorSpace lin_adobergb_scene -o color_interop_id_linear_adobergb.exr")
+command += info_command("color_interop_id_linear_adobergb.exr", safematch=True)
+command += oiiotool("--create 4x4 3 --attrib oiio:ColorSpace unknown_interop_id -o color_interop_id_unknown.exr")
+command += info_command("color_interop_id_unknown.exr", safematch=True)

testsuite/python-colorconfig/ref/out-ocio23.txt

@@ -26,6 +26,8 @@ equivalent('linear', 'lin_srgb'): False
 equivalent('scene_linear', 'lin_srgb'): False
 equivalent('ACEScg', 'scene_linear'): True
 equivalent('lnf', 'scene_linear'): False
+get_color_interop_id('ACEScg') =  lin_ap1_scene
+get_color_interop_id('lin_srgb') =  lin_rec709_scene
 get_color_interop_id([1, 13, 1, 1]) =  srgb_rec709_scene
 get_cicp('pq_rec2020_display') =  [9, 16, 9, 1]
 get_cicp('unknown_interop_id') =  None

testsuite/python-colorconfig/ref/out-ocio24.txt

@@ -26,6 +26,8 @@ equivalent('linear', 'lin_srgb'): False
 equivalent('scene_linear', 'lin_srgb'): False
 equivalent('ACEScg', 'scene_linear'): True
 equivalent('lnf', 'scene_linear'): False
+get_color_interop_id('ACEScg') =  lin_ap1_scene
+get_color_interop_id('lin_srgb') =  lin_rec709_scene
 get_color_interop_id([1, 13, 1, 1]) =  srgb_rec709_scene
 get_cicp('pq_rec2020_display') =  [9, 16, 9, 1]
 get_cicp('unknown_interop_id') =  None

testsuite/python-colorconfig/ref/out-ocio25.txt

@@ -26,6 +26,8 @@ equivalent('linear', 'lin_srgb'): False
 equivalent('scene_linear', 'lin_srgb'): False
 equivalent('ACEScg', 'scene_linear'): True
 equivalent('lnf', 'scene_linear'): False
+get_color_interop_id('ACEScg') =  lin_ap1_scene
+get_color_interop_id('lin_srgb') =  lin_rec709_scene
 get_color_interop_id([1, 13, 1, 1]) =  srgb_rec709_scene
 get_cicp('pq_rec2020_display') =  [9, 16, 9, 1]
 get_cicp('unknown_interop_id') =  None

testsuite/python-colorconfig/src/test_colorconfig.py

@@ -48,6 +48,8 @@
     print ("equivalent('scene_linear', 'lin_srgb'):", config.equivalent("scene_linear", "lin_srgb"))
     print ("equivalent('ACEScg', 'scene_linear'):", config.equivalent("ACEScg", "scene_linear"))
     print ("equivalent('lnf', 'scene_linear'):", config.equivalent("lnf", "scene_linear"))
+    print ("get_color_interop_id('ACEScg') = ", config.get_color_interop_id("ACEScg"))
+    print ("get_color_interop_id('lin_srgb') = ", config.get_color_interop_id("lin_srgb"))
     print ("get_color_interop_id([1, 13, 1, 1]) = ", config.get_color_interop_id([1, 13, 1, 1]))
     print ("get_cicp('pq_rec2020_display') = ", config.get_cicp("pq_rec2020_display"))
     print ("get_cicp('unknown_interop_id') = ", config.get_cicp("unknown_interop_id"))