NOTE: Linear blending is currently disabled in this CL as the
feature is still a work in progress
Android currently performs all blending (any kind of linear math
on colors really) on gamma-encoded colors. Since Android assumes
that the default color space is sRGB, all bitmaps and colors
are encoded with the sRGB Opto-Electronic Conversion Function
(OECF, which can be approximated with a power function). Since
the power curve is not linear, our linear math is incorrect.
The result is that we generate colors that tend to be too dark;
this affects blending but also anti-aliasing, gradients, blurs,
etc.
The solution is to convert gamma-encoded colors back to linear
space before doing any math on them, using the sRGB Electo-Optical
Conversion Function (EOCF). This is achieved in different
ways in different parts of the pipeline:
- Using hardware conversions when sampling from OpenGL textures
or writing into OpenGL frame buffers
- Using software conversion functions, to translate app-supplied
colors to and from sRGB
- Using Skia's color spaces
Any type of processing on colors must roughly ollow these steps:
[sRGB input]->EOCF->[linear data]->[processing]->OECF->[sRGB output]
For the sRGB color space, the conversion functions are defined as
follows:
OECF(linear) :=
linear <= 0.0031308 ? linear * 12.92 : (pow(linear, 1/2.4) * 1.055) - 0.055
EOCF(srgb) :=
srgb <= 0.04045 ? srgb / 12.92 : pow((srgb + 0.055) / 1.055, 2.4)
The EOCF is simply the reciprocal of the OECF.
While it is highly recommended to use the exact sRGB conversion
functions everywhere possible, it is sometimes useful or beneficial
to rely on approximations:
- pow(x,2.2) and pow(x,1/2.2)
- x^2 and sqrt(x)
The latter is particularly useful in fragment shaders (for instance
to apply dithering in sRGB space), especially if the sqrt() can be
replaced with an inversesqrt().
Here is a fairly exhaustive list of modifications implemented
in this CL:
- Set TARGET_ENABLE_LINEAR_BLENDING := false in BoardConfig.mk
to disable linear blending. This is only for GLES 2.0 GPUs
with no hardware sRGB support. This flag is currently assumed
to be false (see note above)
- sRGB writes are disabled when entering a functor (WebView).
This will need to be fixed at some point
- Skia bitmaps are created with the sRGB color space
- Bitmaps using a 565 config are expanded to 888
- Linear blending is disabled when entering a functor
- External textures are not properly sampled (see below)
- Gradients are interpolated in linear space
- Texture-based dithering was replaced with analytical dithering
- Dithering is done in the quantization color space, which is
why we must do EOCF(OECF(color)+dither)
- Text is now gamma corrected differently depending on the luminance
of the source pixel. The asumption is that a bright pixel will be
blended on a dark background and the other way around. The source
alpha is gamma corrected to thicken dark on bright and thin
bright on dark to match the intended design of fonts. This also
matches the behavior of popular design/drawing applications
- Removed the asset atlas. It did not contain anything useful and
could not be sampled in sRGB without a yet-to-be-defined GL
extension
- The last column of color matrices is converted to linear space
because its value are added to linear colors
Missing features:
- Resource qualifier?
- Regeneration of goldeng images for automated tests
- Handle alpha8/grey8 properly
- Disable sRGB write for layers with external textures
Test: Manual testing while work in progress
Bug: 29940137
Change-Id: I6a07b15ab49b554377cd33a36b6d9971a15e9a0b
There is only one caller each for the static functions here so this
CL moves the logic to the caller. Also by moving some of the code
into the pipeline it makes it easier for future changes to configure
how a pipeline handles a layer.
Change-Id: Ib735b5154325cbb658fd151f7a19dbf434ab44b7
std::unique_ptr::release just releases the ownership of the
managed object. To delete the object, std::unique_ptr::reset
function should be called.
Change-Id: If65f74085b1fc2be3a9fffc433326e0bcdb40ff3
Recent changes to mExtensions moved the initialization code from the
constructor to a separate function called load. Make sure to call
this function in the initExtensions function call.
Bug: 25615666
Change-Id: Ic016232c42afefd3b5bc3e4bd5c8428a11c454ad
Bug: 21753739
Includes a revert of 13d1b4ab10fbee5e81a2ba1ac59cfae1e51d3ef0
as that only supported EGL_EXT_buffer_age
Change-Id: Ia86a47d19e3355c067934d7764c330b640c6958d
Bug: 22676664
If a task is queued on a worker thread that is busy
processing a task AND a trim memory signal comes along
prior to the initial task being completed then the
tasks that were queued prior to the exit request will
never be processed.
This is bad, as when those futures are used later on, such
as in trying to delete them from the cache, they will block
waiting for the orphaned task to be finished.
Simple fix is to just never stop the worker threads. Increase
RAM usage slightly as we won't reclaim that stack space, but
this cost is fairly small
Change-Id: I818b011f9bc6ba06942fdad81c27656bd97b42d4
bug:19967854
Separate properties from Caches, into static, RenderThread-only class.
Also rewrites the means for java to set properties to correctly handle
threading, and adds an override for profile bars so that SysUi doesn't clutter
the screen with them.
Change-Id: I6e21a96065f52b9ecc49d1a126244804ba106fa9
Adds remaining missing overrides and nullptr usages, missed due to
an extreme failure in tool usage.
Change-Id: I56abd72975a3999ad13330003c348db40f59aebf
Bug: 18317479
RenderNode::prepareSubTree calls prefetchAndMarkInUse
on every bitmapResoruce in the DisplayList. However,
this resulted in textures being uploaded for bitmaps
that would be drawn from the AssetAtlas instead.
To fix this we teach TextureCache about the AssetAtlas
so that calls to TextureCache return the Texture from
AssetAtlas if it exists. Thus usage of AssetAtlas
is now purely to allow for further optimizations via
draw merging instead of a requirement to get
any benefit at all.
Change-Id: I65282fa05bac46f4e93822b3467ffa0261ccf200
Bug: 17208461
* Switch Layer to be VirtualLightRefBase instead of
Caches' side-channel ref-counting
* Include active layers in gfxinfo dump
* Run gfxinfo dump on the correct thread
* Dump gfxinfo on Layer creation failure
Change-Id: I28d195699e2334518e215ab28c7a17355aee9678
Narrow the use of #include directives in hwui, replacing with forward
declarations where straightforward. Speeds compiles; doesn't do any
restructuring of code.
Change-Id: Icac2baffb5896f55d8c6718e9bd9d4bfa02d3ca0
