This assumptions are now made:
- Internally float buffers are always linear alpha-premul colors
- Readers should worry about delivering float buffers with that
assumptions.
- There's an input image setting to say whether it's stored with
straight/premul alpha on the disk.
- Byte buffers are now assumed have straight alpha, readers should
deliver straight alpha.
Some implementation details:
- Removed scene's color unpremultiply setting, which was very
much confusing and was wrong for default settings.
Now all renderers assumes to deliver premultiplied alpha.
- IMB_buffer_byte_from_float will now linearize alpha when
converting from buffer.
- Sequencer's effects were changed to assume bytes have got
straight alpha. Most of effects will work with bytes still,
however for glow it was more tricky to avoid data loss, so
there's a commented out glow implementation which converts
byte buffer to floats first, operates on floats and returns
bytes back. It's slower and not sure if it should actually
be used -- who're using glow on alpha anyway?
- Sequencer modifiers should also be working nice with straight
bytes now.
- GLSL preview will predivide float textures to make nice shading,
shading with byte textures worked nice (GLSL was assuming straight
alpha).
- Blender Internal will set alpha=1 to the whole sky. The same
happens in Cycles and there's no way to avoid this -- sky is
neither straight nor premul and doesn't fit color pipeline well.
- Straight alpha mode for render result was also eliminated.
- Conversion to correct alpha need to be done before linearizing
float buffer.
- TIFF will now load and save files with proper alpha mode setting
in file meta data header.
- Remove Use Alpha from texture mapping and replaced with image
datablock setting.
Behaves much more predictable and clear from code point of view
and solves possible regressions when non-premultiplied images were
used as textures with ignoring alpha channel.
In the bug report it was also mentioned that special characters should be
preserved for names, however the collada 1.4 specification does not allow this.
Version 1.5 does, but we are still writing 1.4 files and files with such special
characters will then fail to open in some applications.
This commit makes BKE_image_acquire_ibuf referencing result, which means once
some area requested for image buffer, it'll be guaranteed this buffer wouldn't
be freed by image signal.
To de-reference buffer BKE_image_release_ibuf should now always be used.
To make referencing working correct we can not rely on result of
image_get_ibuf_threadsafe called outside from thread lock. This is so because
we need to guarantee getting image buffer from list of loaded buffers and it's
referencing happens atomic. Without lock here it is possible that between call
of image_get_ibuf_threadsafe and referencing the buffer IMA_SIGNAL_FREE would
be called. Image signal handling too is blocking now to prevent such a
situation.
Threads are locking by spinlock, which are faster than mutexes. There were some
slowdown reports in the past about render slowdown when using OSX on Xeon CPU.
It shouldn't happen with spin locks, but more tests on different hardware would
be really welcome. So far can not see speed regressions on own computers.
This commit also removes BKE_image_get_ibuf, because it was not so intuitive
when get_ibuf and acquire_ibuf should be used.
Thanks to Ton and Brecht for discussion/review :)
Replace old color pipeline which was supporting linear/sRGB color spaces
only with OpenColorIO-based pipeline.
This introduces two configurable color spaces:
- Input color space for images and movie clips. This space is used to convert
images/movies from color space in which file is saved to Blender's linear
space (for float images, byte images are not internally converted, only input
space is stored for such images and used later).
This setting could be found in image/clip data block settings.
- Display color space which defines space in which particular display is working.
This settings could be found in scene's Color Management panel.
When render result is being displayed on the screen, apart from converting image
to display space, some additional conversions could happen.
This conversions are:
- View, which defines tone curve applying before display transformation.
These are different ways to view the image on the same display device.
For example it could be used to emulate film view on sRGB display.
- Exposure affects on image exposure before tone map is applied.
- Gamma is post-display gamma correction, could be used to match particular
display gamma.
- RGB curves are user-defined curves which are applying before display
transformation, could be used for different purposes.
All this settings by default are only applying on render result and does not
affect on other images. If some particular image needs to be affected by this
transformation, "View as Render" setting of image data block should be set to
truth. Movie clips are always affected by all display transformations.
This commit also introduces configurable color space in which sequencer is
working. This setting could be found in scene's Color Management panel and
it should be used if such stuff as grading needs to be done in color space
different from sRGB (i.e. when Film view on sRGB display is use, using VD16
space as sequencer's internal space would make grading working in space
which is close to the space using for display).
Some technical notes:
- Image buffer's float buffer is now always in linear space, even if it was
created from 16bit byte images.
- Space of byte buffer is stored in image buffer's rect_colorspace property.
- Profile of image buffer was removed since it's not longer meaningful.
- OpenGL and GLSL is supposed to always work in sRGB space. It is possible
to support other spaces, but it's quite large project which isn't so
much important.
- Legacy Color Management option disabled is emulated by using None display.
It could have some regressions, but there's no clear way to avoid them.
- If OpenColorIO is disabled on build time, it should make blender behaving
in the same way as previous release with color management enabled.
More details could be found at this page (more details would be added soon):
http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.64/Color_Management
--
Thanks to Xavier Thomas, Lukas Toene for initial work on OpenColorIO
integration and to Brecht van Lommel for some further development and code/
usecase review!
