Handle gray alpha conversions in SkSwizzler

Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time Nexus 6P (for a test set of GrayAlpha encoded PNGs)
Regular   Unpremul 0.95x
Zero Init Unpremul 0.94x
Regular   Premul   0.91x
Zero Init Premul   0.90x

BUG=skia:4767
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1665583002

Committed: https://skia.googlesource.com/skia/+/93e613d6bdea05d96e232ed261d7bf886c91bb8e

[msarett, 2016-02-02 23:09:13]

Description was changed from

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

PNG Decode Time (for a test set of GrayAlpha encoded PNGs)
Nexus 6P TBD

BUG=skia:4767
==========

to

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

PNG Decode Time (for a test set of GrayAlpha encoded PNGs)
Nexus 6P TBD

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

[msarett, 2016-02-02 23:15:23]

Description was changed from

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

PNG Decode Time (for a test set of GrayAlpha encoded PNGs)
Nexus 6P TBD

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

to

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time (for a test set of GrayAlpha encoded PNGs)
Nexus 6P TBD

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

[msarett, 2016-02-02 23:36:28]

Description was changed from

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time (for a test set of GrayAlpha encoded PNGs)
Nexus 6P TBD

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

to

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time Nexus 6P (for a test set of GrayAlpha encoded PNGs)
Regular   Unpremul 0.95x
Zero Init Unpremul 0.94x
Regular   Premul   0.91x
Zero Init Premul   0.90x

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

[msarett, 2016-02-02 23:38:59]

msarett@google.com changed reviewers:
+ scroggo@google.com

[scroggo, 2016-02-03 16:11:33]

lgtm

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp
File src/codec/SkPngCodec.cpp (right):

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:388: // srcColorType was determined in read_header()
which determined png color type
suggestedColorType*

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:404: uint8_t encodedColorType =
png_get_color_type(fPng_ptr, fInfo_ptr);
Could be const

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:407: // If encodedColorType is GRAY, there must be a
transparent chunk.
SkASSERT this?

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkSwizzler.cpp
File src/codec/SkSwizzler.cpp (right):

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkSwizzler.cpp#ne...
src/codec/SkSwizzler.cpp:596: while (width > 0 && *src16 == 0x0000) {
Should this have two exit conditions?

- width == 0 : return;
- *src16 == 0x0000 : break (to call proc)

Think that would be faster, slower, or the same?

[msarett, 2016-02-03 17:21:13]

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp
File src/codec/SkPngCodec.cpp (right):

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:388: // srcColorType was determined in read_header()
which determined png color type
On 2016/02/03 16:11:33, scroggo wrote:
> suggestedColorType*

Done.  Comment now reads:
suggestedColorType was determined in read_header() based on the encodedColorType

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:404: uint8_t encodedColorType =
png_get_color_type(fPng_ptr, fInfo_ptr);
On 2016/02/03 16:11:33, scroggo wrote:
> Could be const

Done.

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkPngCodec.cpp#ne...
src/codec/SkPngCodec.cpp:407: // If encodedColorType is GRAY, there must be a
transparent chunk.
On 2016/02/03 16:11:33, scroggo wrote:
> SkASSERT this?

Done.

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkSwizzler.cpp
File src/codec/SkSwizzler.cpp (right):

https://codereview.chromium.org/1665583002/diff/1/src/codec/SkSwizzler.cpp#ne...
src/codec/SkSwizzler.cpp:596: while (width > 0 && *src16 == 0x0000) {
On 2016/02/03 16:11:33, scroggo wrote:
> Should this have two exit conditions?
> 
> - width == 0 : return;
> - *src16 == 0x0000 : break (to call proc)
> 
> Think that would be faster, slower, or the same?

I believe it would be the same.  I just checked the assembly and "proc" gets
inlined.  So the compiler can (and does) make the same optimization that you are
suggesting :).

[msarett, 2016-02-03 18:15:57]

The CQ bit was checked by msarett@google.com

[msarett, 2016-02-03 18:15:57]

The patchset sent to the CQ was uploaded after l-g-t-m from scroggo@google.com
Link to the patchset: https://codereview.chromium.org/1665583002/#ps20001
(title: "Response to comments")

[commit-bot: I haz the power, 2016-02-03 18:16:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1665583002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1665583002/20001

[commit-bot: I haz the power, 2016-02-03 18:17:13]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-02-03 18:17:14]

Try jobs failed on following builders:
  Build-Ubuntu-GCC-Mips-Debug-Android-Trybot on client.skia.compile (JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Mip...)

[msarett, 2016-02-03 18:19:53]

The CQ bit was checked by msarett@google.com

[msarett, 2016-02-03 18:19:53]

The patchset sent to the CQ was uploaded after l-g-t-m from scroggo@google.com
Link to the patchset: https://codereview.chromium.org/1665583002/#ps40001
(title: "Compile in Debug mode :)")

[commit-bot: I haz the power, 2016-02-03 18:19:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1665583002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1665583002/40001

[commit-bot: I haz the power, 2016-02-03 18:44:49]

Description was changed from

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time Nexus 6P (for a test set of GrayAlpha encoded PNGs)
Regular   Unpremul 0.95x
Zero Init Unpremul 0.94x
Regular   Premul   0.91x
Zero Init Premul   0.90x

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

to

==========
Handle gray alpha conversions in SkSwizzler

Nothing fancy here.  By doing the entire conversion ourselves, we
only need to make one conversion pass over each row.  Additionally,
we optimize the premultiply since we know each color component of
the pixel is identical.

This will also enable us to follow up with platform specific
optimizations.

PNG Decode Time Nexus 6P (for a test set of GrayAlpha encoded PNGs)
Regular   Unpremul 0.95x
Zero Init Unpremul 0.94x
Regular   Premul   0.91x
Zero Init Premul   0.90x

BUG=skia:4767
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...

Committed:
https://skia.googlesource.com/skia/+/93e613d6bdea05d96e232ed261d7bf886c91bb8e
==========

[commit-bot: I haz the power, 2016-02-03 18:44:49]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/93e613d6bdea05d96e232ed261d7bf886c91bb8e