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
Addresses the following compile time errors:
In file included from frameworks/base/libs/hwui/LayerRenderer.cpp:24:0:
frameworks/base/libs/hwui/RenderState.h:77:24: error: 'VirtualLightRefBase' has not been declared
void postDecStrong(VirtualLightRefBase* object);
^
In file included from frameworks/base/libs/hwui/LayerCache.h:21:0,
from frameworks/base/libs/hwui/LayerRenderer.cpp:25:
frameworks/base/libs/hwui/Layer.h:55:42: error: expected class-name before '{' token
class Layer : public VirtualLightRefBase {
^
In file included from frameworks/base/libs/hwui/RenderState.cpp:16:0:
frameworks/base/libs/hwui/RenderState.h:77:24: error: 'VirtualLightRefBase' has not been declared
void postDecStrong(VirtualLightRefBase* object);
^
Change-Id: I2be439b373ea356b861f413ff6ce323e8d9baf2d
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
Ignore warnings about unused parameters and initialization of static
constant float data members.
Change one potential error of allocating variable length
array of non-POD element type on stack.
Fix mismatch of class and struct declaration tags.
BUG: 17512760
Change-Id: I3a09c945fb1c17f27aff74a7e439dd4c35d1fb32
bug:17208461
They are destroyed via finalizer-enqueued destroy method, so it's not
valid to check that they've been destroyed at gl context destruction
time.
Change-Id: I670f69825547facd5f31d44acb406418881fee00
bug:15860114
Savelayers and HW layers both now support shadow casting.
For save layers, the light source should always be correct, for HW
layers, the light source position is set when the layer is created,
and updated when it is resized.
Change-Id: Ie85567dd43c2bb0a0b08fd0bd4db41efa793ac2b
Projected RenderNodes are now wrapped with a ClipRect or masked
SaveLayer, so that they are clipped to the outline of the projection
receiver surface.
Change-Id: I1d4afc1bb5d638d650bc0b1dac51a498f216773e
bug:11748993
TextureView should always be drawn with linear filtering if drawing a
buffer sized differently from the layer.
This fixes a bug where TextureViews that were sized differently from
their contents wouldn't be drawn with texture filtering, causing
visible scaling artifacts.
Change-Id: I8a5d27452fe7269ec53896992f37cff51e3ce15a
An array of indices local to a layer would only be necessary if
we changed the way we resolve T-junctions. Since we only ever
draw quads, let's just use the indices we use everywhere else.
This change also uses the global indices array to render list
of colored rectangles to save on the number of vertices generated
CPU-side.
Change-Id: Ia6d1970b0e9247805af5a114ca2a84b5d0b7c282
A clipped saveLayer will cause two draws - first to an onscreen
buffer, then again back to the framebuffer. This change - when in
overdraw debug - reissues draws associated with a clipped saveLayer,
but only to the stencil buffer. Operations within a saveLayer are
shown correctly to be twice drawn, and View.setAlpha() without an
associated hardware layer, or hasOverlappingRendering() are made more
visible.
Hardware layers, on any frame that they are updated, similarly draw
twice, and will also be counted against the stencil buffer doubly.
Note: greater depths of layers - e.g. a saveLayer within a saveLayer -
are not respected, as that would require additional region tracking.
Change-Id: I61fb0e61038fe66013d59914c20bb47a550dea7d
This change uses a new OpenGL ES 3.0 feature to upload less data when
the font cache needs to be update. This can result in significant
performance improvements on device with large textures or with locales
that use a lot of glyphs (CJK for instance.)
This change also fixes various unpack alignment issues. The unpack
alignment, as well as the unpack row length, is not texture specific
but a global state that affect all glTex/SubImage2D calls. Some of
them were missing the appropriate glPixelStorei() call. This could
result in corrupted textures.
Change-Id: Iefb429d4d0d0b4e0faeadf27daafee6d30a21d85
Bug #8378964
This change defers drawing into layers until after the renderer for FBO0
is ready to draw. At that point, all the precaching is done which means
all glyphs can be uploaded at once in the font caches.
Change-Id: Ie1f7a7ff30f76f06fb3dbc72c7d05e66207d1ecb
Bug #7146141
This change is needed to add a render buffer cache to avoid
creating and destroying stencil buffers on every frame.
This change also allows the renderer to use a 1 bit or 4 bit
stencil buffer whenever possible.
Finally this change fixes a bug introduced by a previous CL
which causes the stencil buffer to not be updated in certain
conditions. The fix relies on a new optional parameter in
drawColorRects() that can be used to avoid performing a
quickReject on rectangles generated by the clip region.
Change-Id: I2f55a8e807009887b276a83cde9f53fd5c01199f
Bug #7146141
The GL_QCOM_tiled_rendering extension requires careful use of
start/endTiling when attaching a renderbuffer dynamically.
Change-Id: I20036683ed3909ffaf40cc3d57a25257e35b6fa2
