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
bug:20063841
Restores old SkShader matrix behavior from before the Glop refactor.
Many drawing operations draw without sending the canvas transform to
the GL shader. In such cases, we need to adapt the matrix sent to the
SkShader logic to invert the canvas transform that's built into
the mesh.
Change-Id: I42b6f59df36ce46436322b95bf9ad2140795ee58
Remove Clang cutout for unused parameters. Fix warnings.
Remove Clang cutout for deprecated Skia function usage. Has been
fixed in the L push.
Change-Id: I7ea073ff67127cc1e14e798b655e2c50615fe8e7
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
Instead of duplicating internal info about SkShader, inspect the
SkShader installed on the SkPaint.
core/java/android/view/GLES20Canvas.java:
Remove setupModifiers, nResetModifiers, and nSetupShader.
core/jni/android/graphics/Shader.cpp:
Remove calls to create/destroy the (previously) attached SkiaShader.
core/jni/android_view_GLES20Canvas.cpp:
Remove native code for setupShader and resetModifiers.
graphics/java/android/graphics/BitmapShader.java:
graphics/java/android/graphics/ComposeShader.java:
graphics/java/android/graphics/LinearGradient.java:
graphics/java/android/graphics/RadialGradient.java:
graphics/java/android/graphics/Shader.java:
graphics/java/android/graphics/SweepGradient.java:
Remove code keeping track of native SkiaShader.
libs/hwui/Caches.h:
Include Extensions.h.
libs/hwui/DeferredDisplayList.cpp:
Compare shaders on the paint, instead of on DrawModifiers.
libs/hwui/DisplayList.cpp:
libs/hwui/DisplayList.h:
Remove vector of SkiaShaders.
libs/hwui/DisplayListOp.h:
Access the SkShader on mPaint.
Remove SetupShaderOp and ResetShaderOp.
libs/hwui/DisplayListRenderer.cpp:
libs/hwui/DisplayListRenderer.h:
Remove resetShader, setupShader, refShader, and mShaderMap.
libs/hwui/FontRenderer.cpp:
Pass SkShader to setupDrawShader and setupDrawShaderUniforms.
libs/hwui/OpenGLRenderer.cpp:
libs/hwui/OpenGLRenderer.h:
Add LayerShader, a class inheriting from SkShader, to mimic the
behavior of SkiaLayerShader. Unlike SkiaLayerShader, it can be set on
the SkPaint so it can be inspected later.
Set a LayerShader instead of a SkiaLayerShader.
setupDrawShader and setupDrawShaderUniforms now inspect an SkShader
passed in.
Inspect SkShader instead of mDrawModifiers.mShader.
Remove resetShader and setupShader.
setupDrawColorUniforms now takes a boolean indicating whether there is
a shader.
Add an inline function for accessing the SkShader on an SkPaint.
In setupDrawBlending(Layer*, bool), do not check the shader (which will
never be set), but do check whether the color filter may change the
alpha (newly fixed behavior).
In setupDrawBlending(SkPaint, ...), check the SkShader and whether the
color filter affects alpha (the latter is new behavior).
libs/hwui/Renderer.h:
Remove pure virtual functions setupShader and resetShader.
libs/hwui/ResourceCache.cpp:
libs/hwui/ResourceCache.h:
Remove functions for refing/unrefing shaders.
libs/hwui/SkiaShader.cpp:
libs/hwui/SkiaShader.h:
Much of this code was redundant and has been removed.
Convert structs into class with nothing but static functions for
calling describe/setupProgram.
libs/hwui/TextureCache.cpp:
libs/hwui/TextureCache.h:
Use the SkPixelRef as the key to the bitmap Lru cache, since shader
inspection will provide a different SkBitmap pointer (though it will
hold the correct SkPixelRef with the correct generation ID).
tests/CanvasCompare/src/com/android/test/hwuicompare/DisplayModifier.java:
tests/CanvasCompare/src/com/android/test/hwuicompare/ResourceModifiers.java:
Update manual test to have more shaders: radial, sweep, compose,
invalid compose.
BUG:10650594
Change-Id: Iaa7189178bda1c55f96da044d2a9fa602ba36034
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
mBitmap and mTexture is not initialized to NULL which causes
illegal address access when it fails to be created from
oversized bitmap.
Change-Id: Iea54bec8788bc5f3a10040fdb43f416c0d41a14c
This change removes unnessary symbols. All symbols are hidden by
default, public APIs with exported symbols are explicitly marked
with ANDROID_API.
Change-Id: I692fde432a86c12108de1cfd1f6504919a7d5f3f
This optimization is currently disabled until Launcher is
modified to take advantage of it. The optimization can be
enabled by turning on RENDER_LAYERS_AS_REGIONS in the
OpenGLRenderer.h file.
Change-Id: I2fdf59d0f4dc690a3d7f712173ab8db3848b27b1
This fixes only linear gradients. Sweep and radial gradients, as well as
bitmap shaders, will be fixed in a future commit.
Change-Id: I4eee4ff62e9bbf3b9339fc111a780167449ecfef
This change also adds full support for local transformation matrices on
sweep and radial gradients.
Change-Id: Id8773bc0766575190e3f3d51984fc5e57b266c3f
When an app tries to render a bitmap or path larger than the GPU's maximum
texture size, the drawing command is ignored and a warning is logged. This
change also makes texture drawing more robust by catching potential errors
during texture creation.
This change also fixes a crash in the FontRenderer. The destructor would
sometimes try to free an uninitialized array.
Change-Id: I95ae0939c52192d97b340aa02417bf6d0c962c57
With this change, Skia shaders can easily be applied to any mesh. This change also
supports ComposeShader. For instance, this can be used to blend a gradient and a
bitmap togehter and paint a string of text with the result.
Change-Id: I701c2f9cf7f89b2ff58005e8a1d0d80ccf4a4aea
