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
Fixes: 27941148
Make OffscreenBuffer lifecycle an explicit (and tested) contract between
FrameBuilder and BakedOpRenderer, entirely separate from dispatch. This
makes it safe to reject any rendering work via overdraw content
rejection (before it gets to a BakedOpDispatcher).
Adds a couple tests around OffscreenBuffer leaks, and switches
OffscreenBuffer tests to RENDERTHREAD_TEST macro, as appropriate.
Change-Id: Id114b835d042708ae921028fb4b17e5fa485fe64
Fixes: 27825042
TextureView's matrix may not be set at record time - delay using it
until on RenderThread, when deferring the op.
Change-Id: Icf8b55d656e304ec049ca803b042dc2359482db2
bug:27810783
Previous drawColor->drawPaint conversion failed to preserve unbounded
nature of drawColor from old pipeline.
Change-Id: Ifd7a7b9d645f0887e252e48ca95d3195ee31615f
bug:26591194
Also, revert to using current clip bounds as drawColor/drawPaint bounds
for simplicity in new pipeline.
Change-Id: I1a6b3f9716b564b46df41d57dfe14475fdd24de0
b/26949340 and b/26975469, b/26975079 as well
This reverts commit f276acd98457bcaabc9e79a17a736b3b484f005e.
Change-Id: I4b55177daf0d289bc03604c71fd4bf579f65073a
This CL runs VectorDrawable animation on RenderThread. The changes in this CL
include:
- Convert all the animators in AnimatorSet for AVD into a set of RenderNodeAnimators.
- Hook up the new animators with RenderThread
- Add drawOp in RecordingCanvas for drawing VD so that during the animation
on RenderThread, all the property changes on VD can be reflected on the screen.
TODO:
- Implement reverse and reset for AVD.
Change-Id: I2df1d754f2db0ad098d9c15dde4bb2bdfafc2315
bug:22480459
Also switches std::functions to function pointers on OpReorderer, and
switches AssetAtlas' entry getter methods to using pixelRef pointers,
so it's clear they're the keys.
Change-Id: I3040ce5ff4e178a8364e0fd7ab0876ada7d4de05
Now passes alphas and light radius, and correctly transforms light
center for layers.
Also fixes begin-frame/layer clears to be damage rect aware.
Change-Id: I3b1415cd7bf1518c510145ebebdb745f494a2542
Shares vast majority of clipped savelayer code, with only minor
differences in lifecycle.
Doesn't yet handle fill region, resize, or window transform.
Change-Id: Iabdd71811590d2b937eb11e1b01ce556ade54a5a
Switched from 'renderer/info' to 'dispatcher/renderer' to make their
interaction more natural. The new BakedOpRenderer is more similar in
responsibilities to the OpenGLRenderer, as it manages layer and frame
lifecycles, and performs the actual rendering.
However, it's still simpler because the BakedOpDispatcher handles
mapping Canvas drawing ops to Glops, and the OpReorderer handles almost
all canvas state operations.
Also switch BakedOpRenderer to use the new OffscreenBuffer, which
serves as a lightweight Layer replacement, with a much simpler
lifecycle.
Change-Id: Ie0e2e248503400041d49729d813d485d28c76eb3
clipped SaveLayers will now be pulled to the beginning of the frame,
prior to drawing FBO 0. This will remove the need for switching FBOs
mid-frame.
Change-Id: I4d8dc1f845e84e9b49d5acdf4f4703eef4a9cb06
