In the continuing quest to make create/open more efficient, here are two minor
API changes:
1. In almost all uses, an app calls ImageInput::create() to get an II*, then
immediately calls in->open() to open the file, which, if you think carefully
about the fact that create() does an open to verify that the II is capable of
opening the file, means that open() ends up getting called twice. Very
wasteful. So the first change is that we change the ImageInput::create()
function prototype to include a do_open flag -- if true, it returns the file
already opened, not needing a separate call to open(). If false (and this is
sometimes useful), it behaves as before, returning an ImageInput* that can be
opened, but is not presently. This also simplifies the source of apps just a
bit, since the common "create & open" sequence can now be accomplished with
just a call to create.
2. To further streamline, we add a new optional method,
ImageInput::valid_file(filename), which returns true if the named file appears
to be a valid file of that format (in a way that's less expensive than doing a
full open and header read -- for example, just checking the first few bytes
that contain a "magic number" or whatever). Not all plugins supply this
function, and it's not required; the ones that do must return true for
supports("valid_file"). I've included implementations for OpenEXR and TIFF
that are considerably less expensive than a full header read.
The combination of these should reduce a lot of the overhead for identifying
which type of ImageInput is appropriate for a given file and creating it,
generally avoiding at least one redundant open and header read for exr and tif
files.
Note that this is a break in ABI compatibility. It will not be merged into
1.0, only master, and so will be a 1.1 feature. I believe that it should be
source-back-compatible, however.
You can merge this Pull Request by running:
git pull https://github.com/lgritz/oiio lg-validfile
Or you can view, comment on it, or merge it online at:
https://github.com/OpenImageIO/oiio/pull/265
-- Commit Summary --
* Change ImageInput::create() to allow the caller to request the file to be
returned already opened.
* Make OpenImageIO::geterror() return a thread-specific error, so multiple
threads calling ImageInput::create() can't clobber each other's error messages.
* Add ImageInput::valid_file() and supports("valid_file") -- test whether a
file is a valid file of that format, cheaper than a full open.
-- File Changes --
M src/doc/imageinput.tex (162)
M src/doc/imageioapi.tex (3)
M src/doc/writingplugins.tex (17)
M src/iconvert/iconvert.cpp (2)
M src/igrep/igrep.cpp (13)
M src/iinfo/iinfo.cpp (16)
M src/include/imageio.h (52)
M src/libOpenImageIO/imageio.cpp (25)
M src/libOpenImageIO/imageioplugin.cpp (51)
M src/libtexture/imagecache.cpp (2)
M src/oiiotool/printinfo.cpp (13)
M src/openexr.imageio/exrinput.cpp (20)
M src/python/py_imageinput.cpp (4)
M src/tiff.imageio/tiffinput.cpp (34)
-- Patch Links --
https://github.com/OpenImageIO/oiio/pull/265.patch
https://github.com/OpenImageIO/oiio/pull/265.diff
---
Reply to this email directly or view it on GitHub:
https://github.com/OpenImageIO/oiio/pull/265
--
Larry Gritz
[email protected]
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