AcademySoftwareFoundation/OpenImageIO Release-2.1.9.0

OpenImageIO 2.1.9.0

on GitHub

This is the official transition of the supported production release to 2.1. Some very high level highlights you might want to know about 2.1:

• The primary documentation is now hosted on https://openimageio.readthedocs.io and there you can find both beautiful HTML as well as PDF. A PDF book is no longer included in the distribution. I think everything has transitioned properly, but if you notice anything deficient in the new docs, please let me know.
• We have overhauled the build system, modernized and improved. It is much better at finding, hinting, or excluding individual components and dependent packages. The new build scripts now require a CMake minimum version of cmake 3.12. Please read the notes below for details.
• Support for HEIC/HEIF images.
• A new notation for getting and setting attributes in ParamList and ImageSpec. For details, see #2204 and #2297.
• Improved performance particularly for DPX reading, reading individual frames from movie files, and TextureSystem improvements under high threading.
• Although we still use Travis and Appveyor (for now), much of the CI heavy lifting is now being done by GitHub Actions CI.

We will continue to issue new (compatible) 2.1.x releases approximately monthly, with bug fixes or minor/safe/nonbreaking enhancements.

Detailed release notes are below. Enjoy.

Release 2.1 (8 Dec 2019) -- compared to 2.0

New minimum dependencies:

• CMake minimum is now 3.12. #2348 (2.1.5)

Major new features and performance improvements:

• Support for HEIC/HEIF images. HEIC is the still-image sibling of HEVC
  (a.k.a. H.265), and compresses to about half the size of JPEG but with
  higher visual quality. #2160 #2188 (2.1.0)
• oiiotool new commands: -evaloff -evalon --metamerge --originoffset
• ImageCache/TextureSystem improved perf of the tile and file caches under
  heavy thread contention. In the context of a renderer, we have seen
  improvements of around 7% in overall render time, averaged across a suite
  of typical production scenes. #2314, #2316 (2.1.3) #2381 #2407 (2.1.8)
• Fix huge DPX reading performance regression. Technically this is a bug
  fix that restores performance we once had, but it's a huge speedup.
  #2333 (2.1.4)
• Reading individual frames from very-multi-image files (movie files) has
  been greatly sped up (10x or more). #2345 (2.1.4)

Public API changes:

• ImageSpec new methods getattribute() and getattributetype(). #2204
  (2.1.1)

• ImageSpec and ParamValueList now support operator ["name"] as a way
  to set and retrieve attributes. For example,

  myimagespec["compression"] = "zip";
  myimagespec["PixelAspectRatio"] = 1.0f;
  int dither = myimagespec["oiio:dither"].get<int>();
  std::string cs = myimagespec["colorspace"];
  

  See the documentation about "Attribute Delegates" for more information,
  or the new header attrdelegate.h. #2204 (2.1.1) #2297 (2.1.3)

• ImageSpec::find_attribute now will retrive "datawindow" and "displaywindow"
  (type int[4] for images int[6] for volumes) giving the OpenEXR-like bounds
  even though there is no such named metadata for OIIO (the results will
  assembled from x, y, width, height, etc.). #2110 (2.1.0/2.0.4)

• "Compression" names (where applicable) can now have the quality appended
  to the name (e.g., "jpeg:85") insead of requiring quality to be passed
  as a separate piece of metadata. #2111 (2.1.0/2.0.5)

• Python: define __version__ for the module. #2096 (2.1.0/2.0.4)

• Python error reporting for ImageOutput and ImageBuf.set_pixels
  involving transferring pixel arrays have changed from throwing exceptions
  to reporting errors through the usual OIIO error return codes and queries.
  #2127 (2.1.0/2.0.5)

• New shell environment variable OPENIMAGEIO_OPTIONS can now be used to
  set global OIIO::attribute() settings upon startup (comma separated
  name=value syntax). #2128 (2.1.0/2.0.5)

• ImageInput open-with-config new attribute "missingcolor" can supply
  a value for missing tiles or scanlines in a file in lieu of treating it
  as an error (for example, how OpenEXR allows missing tiles, or when reading
  an incompletely-written image file). A new global OIIO::attribute()
  setting (same name) also accomplishes the same thing for all files read.
  Note that this is only advisory, and not all file times are able to do
  this (OpenEXR is the main one of interest, so that works). #2129 (2.1.0/2.0.5)

• ImageCache::invalidate() and TextureSystem::invalidate() now take an
  optional force parameter (default: true) that if false, will only
  invalidate a file if it has been updated on disk since it was first opened.
  #2133, #2166 (2.1.0/2.0.5)

• New filter name "nuke-lanczos6" matches the "lanczos6" filter from Nuke.
  In reality, it's identical to our "lanczos3", but the name alias is
  supposed to make it more clear which one to use to match Nuke, which uses
  a different nomenclature (our "3" is radius, their "6" is full width).
  #2136 (2.1.0/2.0.5)

• New helper functions in typedesc.h: tostring() converts nearly any
  TypeDesc-described data to a readable string, convert_type() does data
  type conversions as instructed by TypeDesc's. #2204 (2.1.1)

• ImageBuf:

  • Construction from an ImageSpec now takes an optional zero parameter
    that directly controls whether the new ImageBuf should have its buffer
    zeroed out or left uninitialized. #2237 (2.1.2)
  • set_write_format() method has a new flavor that takes a
    cspan<TypeDesc> that can supply per-channel data types. #2239 (2.1.1)

• ColorConfig:

  • Added getColorSpaceFamilyByName(), getColorSpaceNames(),
    getLookNames(), getDisplayNames(), getDefaultDisplayName(),
    getViewNames(), getDefaultViewName(). #2248 (2.1.2)
  • Added Python bindings for ColorConfig. #2248 (2.1.2)

• Formal version numbers are now four parts: MAJOR.MINOR.PATCH.TWEAK.
  #2313,#2319 (2.1.3)

• ImageInput now sets "oiio:subimages" attribute to an int representing the
  number of subimages in a multi-image file -- if known from reading just
  the header. A positive value can be relied upon (including 1), but a
  value of 0 or no such metadata does not necessarily mean there are not
  multiple subimages, it just means it could not be known from inexpensively
  reading only the header. #2344 (2.1.4)

• The imagesize_t and stride_t values now have revised definitions.
  It should be fully API/ABI compatible (at least for 64 bit systems), but
  is a simpler, more modern, more platform-independent definition.
  #2351 (2.1.5)

• DeepData has been altered to make pixel indices and total counts int64_t
  rather than int, in order to be safe for very large images that have > 2
  Gpixels. #2363 (2.1.5)

• On OSX, we now expect non-embedded plugins to follow the convention of
  naming runtime-loaded modules foo.imageio.so (just like on Linux),
  whereas we previously used the convention of foo.imageio.dylib. Turns
  out that dylib is supposed to be only for shared libraries, not runtime
  loadable modules. #2376 (2.1.6)

Fixes and feature enhancements:

• oiiotool:
  • New -evaloff and -evalon lets you disable and enable the expression
    substitution for regions of arguments (for example, if you have an
    input image filename that contains {} brace characters that you want
    interpreted literally, not evaluated as an expression). #2100 (2.1.0/2.0.4)
  • --dumpdata has more intelligible output for uint8 images. #2124
    (2.1.0/2.0.4)
  • Fixed but that could prevent -iconvert oiio:UnassociatedApha 1 from
    correctly propagating to the input reader. #2172 (2.1.0/2.0.6)
  • -o:all=1 (which outputs all subimages to separate files) fixed a
    crash that would occur if any of the subimages were 0x0 (it could
    happen; now it just skips outputting those subimages). #2171 (2.1.0)
  • Improved support of files with multiple subimages: Several commands
    honored -a but did not respect individual allsubimages= modifiers
    (--ch, --sattrib, --attrib, --caption, --clear-keywords,
    --iscolorspace, --orientation, --clamp, -fixnan); Several commands
    always worked on all subimages, but now properly respect -a and
    allsubimages= (--origin, --fullpixels, --croptofull, --trim);
    Several commands were totally unaware of subimages, but now are so and
    respect -a and allsubimages= (--crop, --fullsize, --zover, --fill,
    --resize, --resample). #2202 #2219, #2242 (2.1.1, 2.1.2)
  • --ociodisplay: empty display or view names imply using the default
    display or view. #2273 (2.0.10/2.1.3)
  • --metamerge option causes binary image operations to try to "merge"
    the metadata of their inputs, rather than simply copy the metadata
    from the first input and ignore the others. #2311 (2.1.3)
  • --colormap now supports a new "turbo" color map option. #2320 (2.1.4)
  • Expression evaluation has been extended to support operators // for
    integer division (whereas / is floating point division), and %
    for integer modulus. #2362 (2.1.5)
  • New --originoffset resets the data window origin relative to its
    previous value (versus the existing --origin that sets it absolutely).
    #2369 (2.1.5)
  • --paste has two new optional modifiers: :all=1 pastes the entire
    stack of images together (versus the default of just pasting the top
    two images on the stack), and :mergeroi=1 causes the result to have
    the merged data window of all inputs, instead of the foreground image
    clipping against the boundary of the background image data. #2369 (2.1.5)
  • --paste now works with deep images. #2369 (2.1.5)
  • --paste semantics have changed: the meaning of pasting FG into BG at
    (x,y) now means that the (0,0) origin of FG ends up at (x,y), whereas
    before it placed the corner of FG's data window at (x,y). This will
    not change behavior for ordinary images where FG's data window is (0,0),
    but it makes behavior more sensible for "cropped" or "shrink-wrapped"
    FG images that have non-zero data window origin. #2369 (2.1.5)
  • paste() is now multithreaded and therefore much faster. #2369 (2.1.5)
  • --ociotransform no longer issues an error message when no valid OCIO
    configuration is found (because it's not needed for this operation).
    #2371 (2.1.5)
  • --compare would fail to notice differences in deep images where the
    corresponding pixels had differing numbers of samples. #2381 (2.1.8)
• ImageBuf/ImageBufAlgo:
  • IBA::channel_append() previously always forced its result to be float,
    if it wasn't previously initialized. Now it uses the uaual type-merging
    logic, making the result the "widest" type of the inputs. #2095
    (2.1.0/2.0.4)
  • IBA resize(), fit(), and resample() are no longer restricted to
    source and destination images having the same numer of channels.
    #2125 (2.1.0/2.0.5)
  • Improve numerical precision of the unpremult/premult part of certain
    color transformations. #2164 (2.1.0)
  • ImageBuf::read() now properly forwards the "progress" parameters
    to any underlying call to read_image. #2196 (2.1.1)
  • The OIIO_DISPATCH_COMMON_TYPES2/3 macros used internally by many IBA
    functions have been expanded to handle a few more cases "natively"
    without conversion to/from float. This may make a few cases of odd
    data type combinations have higher precision. #2203 (2.0.8/2.1.1)
  • IBA resize() fix precision issues for 'double' images. #2211
    (2.0.8/2.1.1)
  • IBA::ociodisplay(): empty display or view names imply using the
    default display or view. #2273 (2.0.10/2.1.3)
  • IBA::fixNonFinite(): fixed impicit float/double casts to half. #2301
    (2.0.10/2.1.3)
  • IBA::color_map(): now supports a new "turbo" color map option.
    #2320 (2.1.4)
  • IBA::paste() now works with deep images. #2369 (2.1.5)
  • paste semantics have changed: the meaning of pasting FG into BG at
    (x,y) now means that the (0,0) origin of FG ends up at (x,y), whereas
    before it placed the corner of FG's data window at (x,y). This will
    not change behavior for ordinary images where FG's data window is (0,0),
    but it makes behavior more sensible for "cropped" or "shrink-wrapped"
    FG images that have non-zero data window origin. #2369 (2.1.5)
  • paste() is now multithreaded and therefore much faster. #2369 (2.1.5)
  • ociotransform() no longer issues an error message when no valid OCIO
    configuration is found (because it's not needed for this operation).
    #2371 (2.1.5)
  • Python ociotransform and ociolook mixed up the names and orders of
    the inverse and unpremult params, making it so that you couldn't
    properly specify the inverse. #2371 (2.1.5)
  • IBA::compare() would fail to notice differences in deep images where
    the corresponding pixels had differing numbers of samples. #2381 (2.1.8)
• ImageInput read_image/scanline/tile fixed subtle bugs for certain
  combination of strides and channel subset reads. #2108 (2.1.0/2.0.4)
• ImageCache / TextureSystem / maketx:
  • More specific error message when tile reads appear to be due to the
    file having changed or been overwritten on disk since it was first
    opened. #2115 (2.1.0/2.0.4)
  • maketx: the -u (update mode) is slightly less conservative now,
    no longer forcing a rebuild of the texture just because the file uses
    a different relative directory path than last time. #2109 (2.1.0/2.0.4)
  • Protection against certain divide-by-zero errors when using
    very blurry latong environment map lookups. #2121 (2.1.0/2.0.5)
  • maketx -u is smarter about which textures to avoid re-making because
    they are repeats of earlier commands. #2140 (2.1.0/2.05)
  • Fix possible maketx crash on Windows due to a stack overflow within
    MSVS's implementation of std::regex_replace! #2173 (2.1.0/2.0.6)
  • TS: New attribute "max_mip_res" limits filtered texture access to MIP
    levels that are no higher than this resolution in any dimension. The
    default is 1<<30, meaning no effective limit. #2174 (2.1.1)
  • Stats now count the number of TS::get_texture_info/IC::get_image_info
    calls, like it did before for texture, etc. #2223 (2.1.1)
  • TS::environment() can resolve subimage by name, as we do for
    texture() and texture3d(). #2263
  • Improvements to error message propagation. (2.1.3)
  • Avoid creating a new thread info struct while resolving udims. #2318
    (2.1.4)
  • Work around bug in OpenEXR, where dwaa/dwab compression can crash when
    used on 1-channel tiled images with a tile size < 16. This can crop up
    for MIP-maps (high levels where rez < 16), so we detect this case and
    switch automatically to "zip" compression. #2378 (2.1.6)
  • When converting images to texture (via maketx or IBA::make_texture),
    correctly handle color space conversions for greyscale images.
    #2400 (2.1.8)
• iv viewer:
  • Image info window now sorts the metadata, in the same manner as
    iinfo -v or oiiotool -info -v. #2159 (2.1.0/2.0.5)
• All command line utilities, when run with just --help, will exit with
  return code 0. In other words, utility --help is not an error.
  #2364 (2.1.5) #2383 (2.1.8)
• Python bindings:
  • Fix inability for Python to set timecode attributes (specifically, it
    was trouble setting ImageSpec attributes that were unnsigned int
    arrays). #2279 (2.0.9/2.1.3)
• Improved performance for ustring creation and lookup. #2315 (2.1.3)
• BMP:
  • Fix bugs related to files with very high resolution (mostly 32 bit
    int overflow issues and care to use 64 bit fseeks). Also speed up
    reading and writing very large files. #2404 (2.1.8)
• DPX:
  • Now recognizes the new transfer/colorimetric code for ADX. #2119
    (2.1.0/2.0.4)
  • Fix potential crash when file open fails. #2186 (2.0.7/2.1.1)
  • Support for reading and writing 1-channel (luma, etc.) images. #2294
    (2.0.10/2.1.3)
  • Fix huge DPX reading performance regression. #2333 (2.1.4)
  • Fix bugs related to int32 math that would lead to incorrect
    behavior in very high-resolution files. #2396 (2.1.3)
• ffmpeg/Movie files:
  • Reading individual frames from very-multi-image files (movie files) has
    been greatly sped up (10x or more). #2345 (2.1.4)
  • Support for reading movie files that (a) contain alpha channels, and
    (b) have bit depths > 8 bits per channel. Previously, such files
    would be read, but would be presented to the app as a 3-channel
    8 bit/channel RGB. #2349 (2.1.5)
• FITS:
  • Fix 16 and 32 bit int pixels which FITS spec says are signed, but we
    were treating as unsigned. #2178 (2.1.0)
• HDR/RGBE:
  • Fix bugs related to files with very high resolution (mostly 32 bit
    int overflow issues and care to use 64 bit fseeks). Also speed up
    reading and writing very large files. #2406 (2.1.8)
• IFF
  • Detect and error requests to open files for writing with resolutions
    too high to be properly supported by IFF files. #2397 (2.1.8)
  • Improve error messages when a file can't be opened. #2398 (2.1.8)
• JPEG:
  • Read-from-memory is now supported via IOProxy use. #2180. (2.1.1)
• JPEG-2000:
  • Disable JPEG-2000 support for the (rare) combination of an older
    OpenJPEG 1.x and EMBEDPLUGINS=0 mode, which was buggy. The solution if
    you really need EMBEDPLUGINS and JPEG-2000 support is to please use
    OpenJPEG >= 2.0. #2183. (2.0.7/2.1.1)
• OpenEXR:
  • Avoid some OpenEXR/libIlmImf internal errors with DWA compression by
    switching to zip for single channel images with certain small tile
    sizes. #2147 (2.1.0/2.0.5)
  • Suppress empty string subimage name (fixes a problem with certain
    V-Ray written multi-part exr images). #2190 (2.1.1/2.0.7)
  • Fixed bug that broke th ability to specify compression of multipart
    OpenEXR files. #2252 (2.1.2)
• PNG:
  • More careful catching and reporting errors and corrupt PNG files.
    #2167 (2.1.0/2.0.6)
  • IOProxy reading is now supported. #2180. (2.1.1)
• PSD:
  • When reading PSD files with multiple PhotoShop "layers", properly set
    ImageSpec x, y to the image plane offset (upper left corner) of the
    layer, and set and metadata "oiio:subimagename" to the layer name.
    #2170 (2.1.0)
• RAW:
  • Clarification about color spaces: The open-with-config hint
    "raw:ColorSpace" is more careful about color primaries versus transfer
    curve. Asking for "sRGB" (which is the default) gives you true sRGB --
    both color primaries and transfer. Asking for "linear" gives you
    linear transfer with sRGB/Rec709 primaries. The default is true sRGB,
    because it will behave just like JPEG. #2260 (2.1.2)
  • Added "raw:half_size" and "raw:user_mul" configuration attributes.
    #2307 (2.1.3)
• RLA:
  • Improved logic for determining the single best data type to report
    for all channels. #2282 (2.1.3)
• SGI:
  • Fix bugs when writing extremely high resolution images, due to
    internal 32 bit arithmetic on file offsets. #2402 (2.1.8)
  • Speed up reading and writing of SGI files. #2402 (2.1.8)
• Targa:
  • Put in checks to detect and error requests to write Targa with
    resolutions too high to be supported by the format. #2405 (2.1.8)
• TIFF:
  • Fix problems with JPEG compression in some cases. #2117 (2.1.0/2.0.4)
  • Fix error where reading just a subset of channels, if that subset did
    not include the alpha channel but the image was "unassociated alpha",
    the attempt to automatically associate (i.e. "premultiply" the alpha)
    upon read would get bogus values because the alpha channel was not
    actually read. Now in this case it will not do the premultiplication.
    So if you are purposely reading RGB only from an RGBA file that is
    specifically "unassociated alpha", beware that you will not get the
    automatic premultiplication. #2122 (2.1.0/2.0.4)
  • More careful check and error reporting when user tries to request
    writing to a TIFF file mixed channel data types (which is not supported
    by the underlying libtiff). #2112 (2.1.0/2.0.5)
  • Fix crash reading certain old nconvert-written TIFF files.
    #2207 (2.0.8/2.1.1)
  • Fix bugs when reading TIFF "cmyk" files. #2292. (2.0.10/2.1.3)
  • Correctly handle read and write of 6, 14, and 24 bit per sample
    images. #2296 (2.1.3)
  • Fix potential deadlock in TIFF I/O: minor flaw with threadpool method
    #2327 (2.1.4)
• WebP:
  • Fix bug that gave totally incorrect image read for webp images that
    had a smaller width than height. #2120 (2.1.0/2.0.4)
• zfile:
  • Put in checks to detect and error requests to write zfiles with
    resolutions too high to be supported by the format. #2403 (2.1.8)
• Fix potential threadpool deadlock issue that could happen if you were
  (among possibly other things?) simultaneously calling make_texture from
  multiple application threads. #2132 (2.1.0/2.0.4)
• ImageInput/ImageOutput create() now properly lets you specify the type
  for reader/writer from the format name itself (versus just the extension,
  for example "openexr" versus "exr"). #2185 (2.1.1)
• Make all the various "could not open" messages across the writers use the
  same phrasing. #2189 (2.1.1)
• Better care in some image readers/writers to avoid errors stemming from
  integer overflow when compting the size of large images. #2232 (2.1.2)

Build/test system improvements and platform ports:

• Major overhaul of the CMake build system now that our CMake minimum is
  3.12. #2348 #2352 #2357 #2360 #2368 #2370 #2372 #2373 (2.1.5) #2392 (2.1.8)
  Highlights:
  • All optional dependencies (e.g. "Pkg") now can be disabled (even if
    found) with cmake -DUSE_PKG=0 or environment variable USE_PKG=0.
    Previously, some packages supported this, others did not.
  • All dependencies can be given find hints via -DPkg_ROOT=path or by
    setting environment variable Pkg_ROOT=path. Previously, some did, some
    didn't, and the ones that did had totally inconsistent names for the
    path hint variable (PKG_HOME, PKG_ROOT_DIR, PKG_PATH, etc).
  • Nice color coded status messages making it much more clear which
    dependencies were found, which were not, which were disabled.
  • Use standard BUILD_SHARED_LIBS to control shared vs static libraries,
    replacing the old nonstandard BUILDSTATIC name.
  • Use correct PUBLIC/PRIVATE marks with target_link_libraries and
    target_include_directories, and rely on cmake properly understanding
    the transitive dependencies.
  • CMAKE_DEBUG_POSTFIX adds an optional suffix to debug libraries.
  • CMAKE_CXX_STANDARD to control C++ standard (instead of our nonstandard
    USE_CPP).
  • CXX_VISIBILITY_PRESET controls symbol visibility defaults now, not
    our nonstandard HIDE_SYMBOLS. And the default is to keep everything
    hidden that is not part of the public API.
  • At config time, ENABLE_<name>=0 (either as a CMake variable or an
    env variable) can be used to disable any individual file format or
    command line utility. E.g., cmake -DENABLE_PNG=0 -DENABLE_oiiotool=0
    This makes it easier to greatly reduce build time if you are 100%
    sure there are formats or components you don't want or need.
  • Config based install and usage.
• Deprecate "missingmath.h". What little of it is still needed (it mostly
  addressed shortcomings of old MSVS releases) is now in fmath.h. #2086
• Remove "osdep.h" header that was no longer needed. #2097
• Appveyor scripts have been overhauled and simplified by relying on
  vcpkg to build dependencies. #2113 (2.1.0/2.0.4)
• Detect and error if builder is trying to use a pybind11 that's too old.
  #2144 (2.1.0/2.0.5)
• New CMake build-time option OIIO_LIBNAME_SUFFIX (default: empty) lets
  you append an optional name to the libraries produced (to disambiguate
  two builds at the same facility or distro, much like you could do before
  for symbols with custom namespaces). #2148 (2.1.0)
• On MacOS 10.14 Mojave, fix warnings during iv compiler about OpenGL
  being deprecated in future releases. #2151 (2.1.0/2.0.5)
• At build time, the Python version used can be controlled by setting the
  environment variable $OIIO_PYTHON_VERSION, which if set will initialize
  the default value of the CMake variable PYTHON_VERSION. #2161 (2.0.5/2.1.0)
• On non-Windows systems, the build now generates a PkgConfig file, installed
  at CMAKE_INSTALL_PREFIX/lib/pkgconfig/OpenImageIO.pc. #2158 (2.0.5/2.1.0)
• A new unit test has been backported from master, which tries to perform a
  series of read/write tests on every file format. In partcular, this tests
  certain error conditions, like files not existing, or the directory not
  being writeable, etc. #2181, #2189 (2.0.8/2.1.1)
• Support for CI tests on CircleCI. #2194 (2.1.1) Retired in #2389 (2.1.8).
• New build-time flag USE_WEBP=0 can be used to disable building WebP
  format support even on platforms where webp libraries are found.
  #2200 (2.1.1)
• Fix compiler warnings on Windows. #2209 #2213 #2214 #2392
• Crashes in the command line utilities now attempt to print a stack trace
  to aid in debugging (but only if OIIO is built with Boost >= 1.65, because
  it relies on the Boost stacktrace library). #2229 (2.0.8/2.1.1)
• Add gcc9 to Travis tet matrix and fix gcc9 related warnings. #2235 (2.1.2)
• VDB reader pulled in the TBB libraries using the wrong CMake variable.
  #2274 (2.1.3)
• The embedded fmt implementation has been updated to fix windows
  warnings. #2280 (2.1.3)
• Improvements for finding certain new Boost versions. #2293 (2.0.10/2.1.3)
• Build fixes for MinGW. #2304, #2308 (2.0.10/2.1.3)
• libraw: Fixes to make it build properly against some changes in the
  libraw development master. #2306 (2.1.3)
• Use GitHub Actions CI. Eliminate Appveyor and some Travis tests.
  #2334 (2.1.4) #2356 (2.1.5) #2395 (2.1.8)
• Updated and improved finding of OpenEXR and build_openexr.bash script
  that we use for CI. #2343 (2.1.4)
• Upgrade the pybind11 verson that we auto-install when not found (to 2.4.2),
  and add logic to detect the presence of some pybind11 versions that are
  known to be (buggily) incompatible with C++11. #2347 (2.1.5)
• Fix errors in very new MSVS versions where it identified a suspicious
  practice of ImageBuf's use of a unique_ptr of an undefined type. Jump
  through some hoops to make that legal. #2350 (2.1.5)
• All Python scripts in the tests have been modified as needed to make them
  correct for both Python 2.7 and 3.x. #2355, #2358 (2.1.5)
• Tests are now safe to run in parallel and in unspecified order. Running
  with env variable CTEST_PARALLEL_LEVEL=[something more than 1] greatly
  speeds up the full testsuite on multi-core machines. #2365 (2.1.5)
• Bump robin map version to latest release (v0.6.2) #2401 (2.1.8)
• Fix compiler warnings in ustring.h when _LIBCPP_VERSION is not defined.
  #2415 (2.1.8.1)
• Bump fmt library to v6.1.0. #2423 (2.1.8.1)

Developer goodies / internals:

• argparse.h:
  • Add unit tests. #2192 (2.1.1)
  • Add "%1" which is like "%*" but its list receives only arguments that
    come before any other dash-led arguments. #2192 (2.1.1)
  • Allow specifiers such as "%d:WIDTH" the part before the colon is the
    type specifier, the part after the colon is the name of the parameter
    for documentation purposes. #2312 (2.1.3)
• attrdelegate.h:
  • New header implements "attribute delegates." (Read header for details)
    #2204 (2.1.1)
• dassert.h:
  • Spruce up assrtion macros: more uniform wording, and use pretty
    function printing to show what function the failure was in. #2262
  • The new preferred assertion macros are OIIO_ASSERT and OIIO_DASSERT.
    The OIIO_ASSERT always tests and prints an error message if the test
    fails, but now only aborts when compiled without NDEBUG defined (i.e.
    no abort for release builds), whereas OIIO_DASSERT is for debug mode
    only and does nothing at all (not even perform the test) in release
    mode. These names and behaviors are preferred over the old ASSERT
    and DASSERT, though those deprecated names will continue for at least
    another major release. #2411 (2.1.8.1)
• filesystem.h:
  • Change many filesystem calls to take string_view arguments. #2388 (2.1.8)
  • New fseek() and ftell() that always use 64 bit offsets to be safe
    for very large files. #2399 (2.1.8)
• fmath.h:
  • safe_mod() does integer modulus but protects against mod-by-zero
    exceptions. #2121 (2.1.0/2.0.5)
  • powwroundup/pow2rounddown have been renamed ceil2/floor2 to reflect
    future C++20 standard. The old names still work, so it's a fully back
    compatible change. #2199 (2.0.8/2.1.1)
  • To match C++20 notation, use rotl() template innstead of separate
    rotl32/rotl64 funnctions. #2299, #2309 (2.1.3)
• platform.h:
  • New OIIO_RETURNS_NONNULL macro implements an attribute that marks
    a function that returns a pointer as guaranteeing that it's never
    NULL. #2150 (2.1.0/2.0.5)
• SHA1.h:
  • Upgraded this embedded code from version 1.8 (2008) to the newest
    release, 2.1 (2012). This fixes some Windows warnings. #2342 (2.1.4)
• simd.h:
  • Added vec4 * matrix44 multiplication. #2165 (2.1.0/2.0.6)
  • Guard against shenanigans when Xlib.h having been included and
    #defineing True and False. #2272 (2.0.9/2.1.3)
• strutil.h:
  • Added excise_string_after_head(). #2173 (2.1.0/2.0.6)
  • Fixed incorrect return type of stof(). #2254 (2.1.2)
  • Added remove_trailing_whitespace() and trim_whitespace(). #2298
    (2.1.3)
  • Strutil::wordwrap() now lets you specify the separation characters
    more flexibly (rather than being hard-coded to spaces as separators).
    #2116 (2.1.0/2.0.4)
  • Strutil::parse_while(). #2139 (2.1.0/2.0.5)
  • Added a variety of join() that allows you to set the number of items
    joined, truncating or padding with default values as needed. #2408
    (2.1.8)
  • Fix join to produce a joined string of float-like values with
    locale-independent formatting. #2408 (2.1.8)
  • Fix vsnprintf to be locale independent. #2410 (2.1.8)
  • New lstrip() and rstrip() are just like the existing strip(),
    but operate only on the beginning/left side or ending/right side of
    the string, respectively. #2409 (2.1.8)
• string_view.h:
  • string_view now adds an optional pos parameter to the find_first_of
    / find_last_of family of methods. #2114 (2.1.0/2.0.4)
• sysutil.h:
  • Added stacktrace() and setup_crash_stacktrace(). (Only functional
    if OIIO is built with Boost >= 1.65, because it relies on the Boost
    stacktrace library). #2229 (2.0.8/2.1.1)
• unittest.h:
  • Add OIIO_CHECK_IMAGEBUF_STATUS() test macro. #2394 (2.1.8)
• unordered_map_concurrent.h:
  • Performance improvement by avoiding redundant hashing of keys, and
    improving the speed and properties of the hash functionn. #2313, #2316
    (2.1.3)
• ustring.h:
  • Bug fix in ustring::compare(string_view), in cases where the
    string_view was longer than the ustring, but had the same character
    sequennce up to the length of the ustring. #2283 (2.0.10/2.1.3)
• Wide use of declaring methods noexcept when we want to promise that
  they won't throw exceptions. #2156, #2243 (2.1.0, 2.1.2)
• Changed all (we think) internal string formatting that expects printf
  formatting notation to use the errorf/sprintf style calls, in anticipation
  of the error/format (no trailing -f) calls to eventually follow the
  std::format/python formatting notation. #2393 (2.1.8)

Notable documentation changes:

• The whole documentation system has been overhauled. The main docs have
  been converted from LaTeX to Sphinx (using Doxygen and Breathe) for
  beautiful HTML as well as PDF docs and automatic hosting on
  https://openimageio.readthedocs.io #2247,2250,2253,2255,2268,2265,2270
• Copyright notices have been changed for clarity and conformance with
  SPDX conventions. #2264
• New GitHub issue templates, making separate issue types for bug reports,
  feature requests, build problems, and questions. #2271,#2346