build: Prepare for branch of 3.1 releases (#4862)

Preparation to create a dev-3.1 branch with this merge.

It will fail the ABI test, that is expected. Immediately after, we'll
update the ABI reference standard for 3.1.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

Author: lgritz

CHANGES.md

@@ -4,9 +4,28 @@ Release 3.1 (target: Sept 2025?) -- compared to 3.0
 - Anticipated release candidate: Sep 1, 2025
 - Anticipated supported release: Sep 15, 2025
 
-### New minimum dependencies and compatibility changes:
+**NOTE:** We anticipate some additional changes to color management to be
+rolled out during the beta period. It will not include any breaks to API or
+ABI compatibility, but we do expect some behavior changes.
+
+**Executive Summary / Highlights:**
+  - New image file support: Ultra HDR (HDR images in JPEG containers).
+  - oiiotool new commands: `--layersplit`, `--pastemeta`, `--demosaic`,
+    `create-dir` and new expression expansion tokens: `IS_CONSTANT`,
+    `IS_BLACK`, `SUBIMAGES`.
+  - New IBA image processing functions: `scale()`, `demosaic`.
+  - New 2-level namespace scheme that we hope will make it possible in the
+    future for our annual releases to NOT need to break backward ABI
+    compatibility.
+  - Support in Python for `ImageBuf._repr_png_` method allows use of OIIO
+    inside [Jupyter Notebooks](https://jupyter.org/) to display computed
+    images.
+  - Color management improvements (some TBD, not landed yet) to conform to
+    Color Interchange Forum and OpenEXR new conventions for naming and
+    specifying color spaces.
 
-- Anticipated raising of Python minimum to 3.9.
+### New minimum dependencies and compatibility changes:
+* *Python*: 3.9 minimum (from 3.7) [#4830](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4830) (3.1.4.0)
 
 ### ⛰️  New features and public API changes:
 * *New image file format support:*
@@ -160,7 +179,8 @@ Release 3.1 (target: Sept 2025?) -- compared to 3.0
     - *build*: Clean up Windows compilation warnings [#4706](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4706) (3.1.3.0)
     - *build/python*: Wheel upload_pypi step should only run from main repo [#4820](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4820) (3.1.3.0)
     - *build*: Fix typo related to finding ccache [#4833](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4833) (3.1.4.0)
-* Dependency support:
+    - *build*: C++23 support [#4844](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4844) (3.1.4.0)
+* Dependency and platform support:
     - *deps*: Support static OCIO self-builds [#4517](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4517) (by zachlewis) (3.1.0.0/3.0.1.0)
     - *deps*: Add new ref output for libheif updates [#4525](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4525) (3.1.0.0/3.0.1.0)
     - *build*: Add build recipe for PNG [#4423](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4423) (by zachlewis) (3.1.0.0/3.0.1.0)
@@ -174,6 +194,11 @@ Release 3.1 (target: Sept 2025?) -- compared to 3.0
     - *tests*: Update ref image for slightly changed freetype accents [#4765](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4765) (3.1.3.0)
     - *deps/ffmpeg*: Replace deprecated and soon removed avcodec_close with avcodec_free_context [#4837](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4837) (by Vlad Erium) (3.1.4.0)
     - *build/jpeg2000*: Update jpeg2000input.cpp to include cstdarg [#4836](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4836) (by Peter Kovář) (3.1.4.0)
+    - *deps*: Raise minimum supported Python from 3.7 to 3.9 [#4830](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4830) (3.1.4.0)
+    - *deps*: Use get_plane2 introduced by libheif 1.20.2 [#4851](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4851) (by toge) (3.1.4.0)
+    - *windows*: Include Windows version information on produced binaries [#4696](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4696) (by Jesse Yurkovich) (3.1.3.0)
+    - windows + ARM64*: Add arm_neon.h include on Windows ARM64 with clang-cl [#4691](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4691) (by Anthony Roberts)
+    - *build/windows*: Propagate CMAKE_MSVC_RUNTIME_LIBRARY [#4842](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4842) (3.1.4.0)
 * Testing and Continuous integration (CI) systems:
     - *tests*: Improve Ptex testing [#4573](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4573) (3.1.1.0)
     - *tests*: Better testing coverage of null image reader/writer [#4578](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4578) (3.1.1.0)
@@ -217,10 +242,7 @@ Release 3.1 (target: Sept 2025?) -- compared to 3.0
     - *ci*: Update linux arm clang reference output [#4782](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4782) (3.1.3.0)
     - *ci*: Bump 'latest releases' tests to use pybind11 3.0.0 [#4828](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4828) (3.1.4.0)
     - *ci*: For python stub generation, lock pybind11 to pre-3.0 [#4831](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4831) (3.1.4.0)
-* Platform support:
-    - *windows*: Include Windows version information on produced binaries [#4696](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4696) (by Jesse Yurkovich) (3.1.3.0)
-    - windows + ARM64*: Add arm_neon.h include on Windows ARM64 with clang-cl [#4691](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4691) (by Anthony Roberts)
-    - *build/windows*: Propagate CMAKE_MSVC_RUNTIME_LIBRARY [#4842](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4842) (3.1.4.0)
+    - *ci*: Add a VFX Platform 2026 CI job [#4856](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4856) (3.1.4.0)
 
 ### 📚  Notable documentation changes:
   - *docs*: Clarify 'copy_image' example [#4522](https://github.com/AcademySoftwareFoundation/OpenImageIO/pull/4522) (3.1.0.0/3.0.1.0)

CMakeLists.txt

@@ -19,12 +19,12 @@ project (OpenImageIO VERSION ${OpenImageIO_VERSION}
 set (PROJ_NAME OIIO)    # short name, caps
 string (TOLOWER ${PROJ_NAME} PROJ_NAME_LOWER)  # short name lower case
 string (TOUPPER ${PROJ_NAME} PROJ_NAME_UPPER)  # short name upper case
-set (PROJECT_VERSION_RELEASE_TYPE "dev" CACHE STRING
+set (PROJECT_VERSION_RELEASE_TYPE "beta" CACHE STRING
     "Build type, for example: dev, beta2, RC1 (empty string for normal release)")
 set (${PROJECT_NAME}_VERSION_RELEASE_TYPE ${PROJECT_VERSION_RELEASE_TYPE})
 set (PROJECT_AUTHORS "Contributors to the OpenImageIO project")
 option (${PROJECT_NAME}_SUPPORTED_RELEASE
-        "Set ON for supported release branches, OFF for 'main'" OFF)
+        "Set ON for supported release branches, OFF for 'main'" ON)
 if (${PROJECT_NAME}_SUPPORTED_RELEASE)
     set (${PROJECT_NAME}_DEV_RELEASE OFF)
 else ()
@@ -40,7 +40,7 @@ if (CMAKE_VERSION VERSION_LESS 3.21)
     endif ()
 endif ()
 
-# Set up module path for our own cmake modules and add some esential ones
+# Set up module path for our own cmake modules and add some essential ones
 list (APPEND CMAKE_MODULE_PATH
       "${PROJECT_SOURCE_DIR}/src/cmake/modules"
       "${PROJECT_SOURCE_DIR}/src/cmake")

INSTALL.md

@@ -17,8 +17,9 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
  * C++17 or higher (also builds with C++20 and C++23)
      * The default build mode is C++17. This can be controlled by via the
        CMake configuration flag: `-DCMAKE_CXX_STANDARD=20`, etc.
- * Compilers: gcc 9.3 - 14.2, clang 5 - 20, MSVS 2017 - 2022 (v19.14
-   and up), Intel icc 19+, Intel OneAPI C++ compiler 2022+.
+ * Compilers: gcc 9.3 - 14.2, clang 5 - 20 (though we don't actively test
+   older than 11), MSVS 2017 - 2022 (v19.14 and up), Intel icc 19+, Intel
+   OneAPI C++ compiler 2022+.
  * CMake >= 3.18.2 (tested through 4.1)
  * Imath >= 3.1 (tested through 3.2 and main)
  * OpenEXR >= 3.1 (tested through 3.4 and main)

src/doc/Doxyfile

@@ -2187,10 +2187,13 @@ PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
                          OIIO_NAMESPACE_END="}" \
                          OIIO_NAMESPACE_3_0_BEGIN="namespace OIIO {" \
                          OIIO_NAMESPACE_3_0_END="}" \
+                         OIIO_NAMESPACE_3_1_BEGIN="namespace OIIO {" \
+                         OIIO_NAMESPACE_3_1_END="}" \
                          OIIO_NS_BEGIN="namespace OIIO {" \
                          OIIO_NS_END="}" \
                          OIIO_CONSTEXPR17=constexpr \
                          OIIO_CONSTEXPR20=constexpr \
+                         OIIO_CONSTEXPR23=constexpr \
                          OIIO_IB_DEPRECATE_RAW_PTR:= \
                          OIIO_INLINE_CONSTEXPR="inline constexpr" \
                          OIIO_PURE_FUNC= \

src/include/OpenImageIO/oiioversion.h.in

@@ -173,10 +173,9 @@ namespace OIIO = @PROJ_NAMESPACE@;
 #define OIIO_NS_BEGIN(ver) namespace @PROJ_NAMESPACE@ { namespace ver {
 #define OIIO_NS_END } }
 
-// Specialty macro: Make something ABI compatible with 3.0
-#define OIIO_NAMESPACE_3_0 @PROJ_NAMESPACE@_v3_0
-#define OIIO_NAMESPACE_3_0_BEGIN namespace OIIO_NAMESPACE_3_0 {
-#define OIIO_NAMESPACE_3_0_END }
+// Specialty macro: Make something ABI compatible with 3.1
+#define OIIO_NAMESPACE_3_1_BEGIN OIIO_NS_BEGIN(v3_1)
+#define OIIO_NAMESPACE_3_1_END OIIO_NS_END
 
 // Macro to use names without explicit qualifier
 #define OIIO_NAMESPACE_USING using namespace @PROJ_NAMESPACE@::@PROJ_VERSION_NAMESPACE@;