This change also fixes an issue with RGBA16F bitmaps when modulated
with a color (for instance by setting an alpha on the Paint object).
The color space conversion is currently done entirely in the shader,
by doing these operations in order:
1. Sample the texture
2. Un-premultiply alpha
3. Apply the EOTF
4. Multiply by the 3x3 color space matrix
5. Apply the OETF
6. Premultiply alpha
Optimizations:
- Steps 2 & 6 are skipped for opaque (common) bitmaps
- Step 3 is skipped when the color space's EOTF is close
to sRGB (Display P3 for instance). Instead, we use
a hardware sRGB fetch (when the GPU supports it)
- When step 3 is necessary, we use one of four standard
EOTF implementations, to save cycles when possible:
+ Linear (doesn't do anything)
+ Full parametric (ICC parametric curve type 4 as defined
in ICC.1:2004-10, section 10.15)
+ Limited parametric (ICC parametric curve type 3)
+ Gamma (ICC parametric curve type 0)
Color space conversion could be done using texture samplers
instead, for instance 3D LUTs, with or without transfer
functions baked in, or 1D LUTs for transfer functions. This
would result in dependent texture fetches which may or may
not be an advantage over an ALU based implementation. The
current solution favor the use of ALUs to save precious
bandwidth.
Test: CtsUiRenderingTests, CtsGraphicsTests
Bug: 32984164
Change-Id: I10bc3db515e13973b45220f129c66b23f0f7f8fe
This is the first step toward interpreting color spaces at render time.
Bug: 32984164
Test: BitmapColorSpaceTest in CtsGraphicsTestCases
Change-Id: I0164a18f1ed74a745874fe5229168042afe27a04
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
* Add explicit keyword to conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
Test: build with WITH_TIDY=1
Change-Id: Iab3e6636f60a70cb124f29dc19f20f842fa8dfda
am: b2e36d7939
* commit 'b2e36d7939610de538a6ec95a821b61b365b3073':
Use LUT for computing final shadow alpha
Change-Id: Ia17e3b93e9ade0633aee5a1e9edd60b92dd1e062
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
Full GLES error checking layer via -include
trickery. Change DEBUG_OPENGL to a level system.
HIGH = every GL call is error checked
MODERATE = checkpointing at interesting spots
LOW = only asserts there are no errors at the end of a frame
or when the FBO changes
NONE = AIN'T GOT NO TIME FOR ERRORS GOTTA GO FAST!
Change-Id: Ibe81aae93d942059c4ddf1cbb11c828b7ce4c10b
Bug: 26584230
activateTexture(0) was accidentally refactored into
Texture::upload. Only OffscreenBuffer intended for the
texture unit to change
Change-Id: I5dbfc3eab8843733084ce1ce38a0a946abf0e05b
When there is not enough space and we cannot delete any
Texture in TextureCache to secure space, a new Texture is
created over and over again for the same SkBitmap and
there is the case that it is not deleted.
This patch avoids such cases.
Change-Id: Ic5353995e6d0716c31fe3bb49c60ec1a71574643
Signed-off-by: Dohyun Lee <leedhyun11@gmail.com>
Several places were setting GL_UNPACK_ALIGNMENT
unneccessarily, whereas other places were assuming an
unpack alignment of 1. Since we never actually
do explicit row-alignment, set GL_UNPACK_ALIGNMENT
to 1 at context creation time and never change it
Bug: 26584230
Also turns on aggressive glGetError checking to
better catch potential problem zones
Change-Id: I190c8f0f0494a7f046d5ed769405c75d363be59a
DeferredLayerUpdater always did a post to delete itself, which
would result in the test thinking it had leaked an object since
it wasn't deleted when it returned. Fix this by deleting immediately
if we're already on the right thread.
Remove RenderState's requireGlContext assert as it's now
covered by GpuMemoryTracker, which is also more test friendly.
RenderState's assert required an actual EGL context, which we
don't mock away in unit tests.
Change-Id: Ic23eb54e7151355f7acca483d7464350c9d6a87f
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
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
