It was caused by image threading safe commit and it was noticeable
only on really multi-core CPU (like dual-socket Xeon stations), was
not visible on core i7 machine.
The reason of slowdown was spinlock around image buffer referencing,
which lead to lots of cores waiting for single core and using image
buffer after it was referenced was not so much longer than doing
reference itself.
The most clear solution here seemed to be introducing Image Pool
which will contain list of loaded and referenced image buffers, so
all threads could skip lock if the pool is used for reading only.
Lock only needed in cases when buffer for requested image user is
missing in the pool. This lock will happen only once per image so
overall amount of locks is much less that it was before.
To operate with pool:
- BKE_image_pool_new() creates new pool
- BKE_image_pool_free() destroys pool and dereferences all image
buffers which were loaded to it
- BKE_image_pool_acquire_ibuf() returns image buffer for given
image and user. Pool could be NULL and in this case fallback to
BKE_image_acquire_ibuf will happen.
This helps to avoid lots to if(poll) checks in image sampling
code.
- BKE_image_pool_release_ibuf releases image buffer. In fact, it
will only do something if pool is NULL, in all other case it'll
equal to DoNothing operation.
This codec is absolutely needed to generate DCP using OpenDCP,
before that external application to convert JP2 to J2K was used
which slowed down export a lot.
New codec is exposed to image format settings panel and called
Codec. Default one is JP2 which creates files with .jp2 extension,
new one is called J2K which creates with .j2c extension.
Other changes:
- Fixed avi jpeg warning which was treating as error here.
- Made it so extension is detecting from ImageFormatData instead
of image file type, which makes it possible to have different
extension for the same file type depending on it's settings.
IRIS format should still be changed (depending on number of
channels it'll be .bw, .rgb or .rgba extension)
- Default image format settings would be set from image buffer
when re-saving it. Makes it possible to easily open .j2c file
and save it using J2K codec (without this change it'll save as
.jp2 using JP2 codec)
