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
If we created a BROWSE PendingIntent early during boot (while the
device was still locked), we would resolve the MIME type as "null"
meaning the intent would fail to launch.
Since we always know what the MIME type will be, set it explicitly.
Test: boot device while USB device attached
Bug: 30742481
Change-Id: I23c523cbe2660ca63a3b7df1f41300ab803b314c
Animators can be scaled to have zero duration globally in any device.
This can happen either via Developer Options (an uncommon path) or
Battery Saver mode (much more common for real users).
In general, this works fine; it just causes app animations to be jump-cuts
instead (which is the desired effect, either to make transitions faster
(Developer Options setting) or to optimize battery usage by rendering
fewer frames (Battery Saver mode).
But sometimes, choreographed animations can have undesired artifacts. For
example, an animation that calls an end listener to restart itself
will end up doing this almost constantly due to this effect. Other artifacts
can also occur, such as intermediate results in a complex choreography of
multiple animations can show several intermediate results in a way that is
confusing to the user.
For these cases, there is nothing that the platform can do to automatically
determine how to best handle the result. Instead, we surface this new
API to help developers discover this behavior and compensate accordingly.
Bug: 31052471 Animation playback is abnormally fast during Battery saver mode
Test: unit tests, CTS test upcoming
Change-Id: Id7ef1a9652ac5c6cdaca0c126756e82582d49b1c
Just the basic cleanup first, will follow-up with a more
comprehensive update later
Test: builds & boots, refactor no behavior change
Change-Id: Ie3a7144b5fefdfda085e2ab50da8b0e627a1ecb8
Also fixes progress bar sample tile to reflect density and ensures
that ProgressBar.tileify() clones inner drawables into the correct
density.
Bug: 31841123
Test: BitmapDrawableTest#testPreloadDensity()
Test: ThemeHostTest
Test: Visual inspection of ApiDemos
Change-Id: I9dcb9817d8d91d61ff0215987247e9e7fb089c46
Added a convenience mechanism to delete the whole database if it is of
a version that is so old that the application does not want to support
upgrading it. SQLiteOpenHelper now automatically deletes such a database
and creates a fresh one with the newest version provided. A callback
onBeforeDelete is added if the application wants to collect some data
from the db before it is deleted.
Test: Tested by upgrading contacts database using ContactsDatabaseHelper
Bug: 31559016
Change-Id: I3f924d247cdca2015c4244cc987de2538a086651
MessagingStyle expects the field userReplyName to be non-null, but the
documentation doesn't describe it as such. This updates the documentation
to say the field is required, and adds a NonNull annotation.
This has no behavior changes.
BUG:31747744
Change-Id: If832d059c276e856fba366dabfa8a5821bb63054
Implement it in ExternalStorageProvider.
Bug: 30948740
Change-Id: I1b7717a794ae3892cd1be5ed90ca155adf9a64f4
(cherry picked from commit 51efc73f3f341393cf93f71604be791205021b69)
