From 8b88bc777cb6777201db26209044f0b1f0650108 Mon Sep 17 00:00:00 2001
From: Cary Phillips <cary@ilm.com>
Date: Thu, 14 Sep 2023 10:47:53 -0700
Subject: [PATCH] Omit OPENEXR_IMAGES_TAG from test image url if empty

This allows the url for the test images to reference a local file:

  cmake -DOPENEXR_IMAGES_REPO=file:///my/clone/of/openexr-images -DOPENEXR_IMAGES_TAG=""

which avoids the remote downloading of the test images at cmake time.

Also, mention the test images in the install docs.

Signed-off-by: Cary Phillips <cary@ilm.com>
---
 src/test/bin/CMakeLists.txt |  8 ++++++--
 website/install.rst         | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/test/bin/CMakeLists.txt b/src/test/bin/CMakeLists.txt
index 37e40b3cfb..e53b87900f 100644
--- a/src/test/bin/CMakeLists.txt
+++ b/src/test/bin/CMakeLists.txt
@@ -16,8 +16,12 @@ if(BUILD_TESTING)
 
   set(OPENEXR_IMAGES_TAG "v1.0" CACHE STRING "Bin test image repo tag")
 
-  set(images_url ${OPENEXR_IMAGES_REPO}/${OPENEXR_IMAGES_TAG})
-
+  if ("${OPENEXR_IMAGES_TAG}" STREQUAL "")
+    set(images_url ${OPENEXR_IMAGES_REPO})
+  else()
+    set(images_url ${OPENEXR_IMAGES_REPO}/${OPENEXR_IMAGES_TAG})
+  endif()
+  
   set(images 
       TestImages/GrayRampsHorizontal.exr
       LuminanceChroma/Garden.exr
diff --git a/website/install.rst b/website/install.rst
index 3d26194122..d6bee180bb 100644
--- a/website/install.rst
+++ b/website/install.rst
@@ -329,6 +329,30 @@ shared object is produced.
   ``OPENEXR_DEFLATE_TAG``. This means do *not* use any existing
   installation of ``libdeflate``.
 
+Test Images Dependency
+~~~~~~~~~~~~~~~~~~~~~~
+
+The OpenEXR test suite relies on images from the `online test image
+gallery
+<https://github.com/AcademySoftwareFoundation/openexr-images>`_, which CMake
+automatically downloads during configuration.  You can provide an
+alternate location for the test images via the ``OPENEXR_IMAGES_REPO``
+and ``OPENEXR_IMAGES_TAG`` variables.
+
+* ``OPENEXR_IMAGES_REPO`` and ``OPENEXR_IMAGES_TAG``
+
+  The images repo to auto-fetch for the test suite, and the tag to
+  sync it to.  The default repo is
+  ``https://github.com/AcademySoftwareFoundation/openexr-images.git``
+  and the tag is ``v1.0``. 
+
+Note that you can void downloading images by specifying a repo on the
+local filesystem via a ``file:`` url:
+
+.. code-block::
+
+    cmake -DOPENEXR_IMAGES_REPO=file:///my/clone/of/openexr-images -DOPENEXR_IMAGES_TAG=""
+
 Namespace Options
 ~~~~~~~~~~~~~~~~~