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
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
Float textures offer better precision for dithering.
In addition this change removes two uniforms from gradient shaders.
These uniforms were used to dither gradients but their value is
a build time constant. Instead we hardcode the value directly in
the shader source at compile time.
Change-Id: I05e9fd3eef93771843bbd91b453274452dfaefee
Add a key manipulation that makes black text/paths use the standard
simple bitmap/patch shader, since they are the same. Previously we'd
create a separate shader for each because the keys differed, even
though the shaders were functionally equivalent.
Also fixes some issues around setting DEBUG_PROGRAM
Change-Id: I0c77c684d58da03501ee9ab8239c7d4a70fd6b5c
Bug #4343984
TextureView can be used to render media content (video, OpenGL,
RenderScript) inside a View.
The key difference with SurfaceView is that TextureView does
not create a new Surface. This gives the ability to seamlessly
transform, animate, fade, etc. a TextureView, which was hard
if not impossible to do with a SurfaceView.
A TextureView also interacts perfectly with ScrollView,
ListView, etc. It allows application to embed media content
in a much more flexible way than before.
For instance, to render the camera preview at 50% opacity,
all you need to do is the following:
mTextureView.setAlpha(0.5f);
Camera c = Camera.open();
c.setPreviewTexture(mTextureView.getSurfaceTexture());
c.startPreview();
TextureView uses a SurfaceTexture to get the job done. More
APIs are required to make it easy to create OpenGL contexts
for a TextureView. It can currently be done with a bit of
JNI code.
Change-Id: Iaa7953097ab5beb8437bcbbfa03b2df5b7f80cd7
Draw anti-aliased lines with OpenGL by constructing a quad with
a border that fades out (to mimic fragment coverage).
Change-Id: Ib81a3e62d663acdf1b46b401ac4aa7ee9855cc7e
Bug #4092053
The problem always existed but was made visible by partial invalidation.
When saving a layer, the renderer would try to postpone glClear()
operations until the next drawing command. This however does not work
since the clip might have changed. The fix is rather simple and
simply gets rid of this "optimization" (that turned out to be
usless anyway given how View issues saveLayer() calls.)
This change also fixes an issue with gradients (color stops where
not properly computed when using a null stops array) and optimizes
display lists rendering (quickly rejects larger portions of the
tree to avoid executing unnecessary code.)
Change-Id: I0f5b5f6e1220d41a09cc2fa84c212b0b4afd9c46
This is the first step of the refactoring:
- drawColorRect
- drawTextureMesh
Remaining methods to refactor:
- setupTextureAlpha8
- drawPath
- setupShadow
- drawText
- drawLines
- composeLayerRegion
Change-Id: I0fced6a05b6b6eee10ee7cef0c3fbdaa6cefab20
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 adds the ability to blend with the framebuffer using Darken,
Lighten, Add, Multiply, Overlay and Screen.
Change-Id: Iae01a53797d4ad39c373cba6ff2a42293129da1a
This change adds the following blending modes for shaders and color filters:
Add
Multiply
Screen
Overlay
Darken
Lighten
Change-Id: Iff22f5ce6041b43c71b1857d73013f5010ab3413
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
The generator supports features that are not yet implement in the
renderer: color matrix, lighting, porterduff color blending and
composite shaders.
This change also adds support for repeated/mirrored non-power of 2
bitmap shaders.
Change-Id: I903a11a070c0eb9cc8850a60ef305751e5b47234
With this change, all the vertex and fragment shaders used by the GL
renderer are now generated based on a program description supplied
by the caller. This allows the renderer to generate a large number
of shaders without having to write all the possible combinations by
hand. The generated shaders are stored in a program cache.
Change-Id: If54d286e77ae021c724d42090da476df12a18ebb
