Android Android Android Android 硬件加速的硬件加速的硬件加速的硬件加速的2D2D2D2D绘图研究绘图研究绘图研究绘图研究Android HW Accelerated 2D RenderingAndroid HW Accelerated 2D RenderingAndroid HW Accelerated 2D RenderingAndroid HW Accelerated 2D Rendering

RogerRogerRogerRogeryixx@ucweb.comroger2yi@gmail.comwww.twitter.com/roger2yihttps://plus.google.com/

2011-12-20 Roger, UC

Introduction

2011-12-20 Roger, UC

HW Accelerated 2D RenderingHW Accelerated 2D RenderingHW Accelerated 2D RenderingHW Accelerated 2D Rendering

• 硬件加速的2D绘图主要包括两个方面

– 基本图元绘制（Primitive Drawing - Shape，Text，Image）

– 图层混合（Layer/Surface Composite）

2011-12-20 4

Some Android Graphics True Facts...Some Android Graphics True Facts...Some Android Graphics True Facts...Some Android Graphics True Facts...

• 从Android 1.0开始，窗口混合就开始使用硬件加速

– 右图包含了4个窗口，分别是 - 状态栏，壁纸，lanucher和菜单

– 像通知栏的拖拉，Activities的切换动画，菜单，对话框的弹出/消失动画都使用了硬件加速进行窗口混合

• 在Android 3.0之后，窗口内部的内容绘制（Canvas）才开始支持硬件加速

2011-12-20 Roger, UC

Controlling Hardware AccelerationControlling Hardware AccelerationControlling Hardware AccelerationControlling Hardware Acceleration

• Application

• Activity

• Window

• View

2011-12-20 Roger, UC

Application LevelApplication LevelApplication LevelApplication Level

• Android 3.x 默认为false

• Android 4.x 默认为true（可以通过系统设置关闭）

2011-12-20 Roger, UC

Activity/Window LevelActivity/Window LevelActivity/Window LevelActivity/Window Level

• Window Level 只能开不能关

• 可以在清单文件中设置Activity关闭，然后根据运行时Intent传入的参数再打开窗口的硬件加速

2011-12-20 Roger, UC

View LevelView LevelView LevelView Level

• 将View的Layer Type设置为SW Layer，可以使View创建一个内部的位图缓存，View的内容先绘制到位图，然后再把位图拷贝到Window Surface上

• 相当于关闭该View的硬件加速绘图

2011-12-20 Roger, UC

View Layer TypeView Layer TypeView Layer TypeView Layer Type

• 在Android 3.0+后，View一共有3种Layer Type– None，默认类型，View的内容直接绘制到Window

Surface上面

– SW Layer，创建一个内部的位图缓存，View的内容先绘制到位图，然后再把位图拷贝到Window Surface上

– HW Layer，创建一个内部的硬件加速的帧缓存，View的内容先绘制到帧缓存，然后再拷贝到Window Surface上，只有在Window是硬件加速时才支持，否则自动变为SW Layer

2011-12-20 Roger, UC

2D Rendering Mode2D Rendering Mode2D Rendering Mode2D Rendering Mode

• 在Android 3.0后，一共有5种主要的2D渲染模式，1主要用于游戏，2，3，4都可以用于一般的View Hierachy渲染，5主要用于动画和实时交互场景1.通过SurfaceHolder获得Window或者SurfaceView的

Surface Canvas（SurfaceHolder.lockCanvas），在单独的Render Thread中绘图

2.Window Surface硬件加速，View的Layer Type为None，在主线程（UI线程）中绘图（View.onDraw）

2011-12-20 Roger, UC

Cont.Cont.Cont.Cont.

3.Window Surface非硬件加速，View的Layer Type为None，在主线程（UI线程）中绘图（View.onDraw）

4.Window Surface硬件加速，View的Layer Type为SW，在主线程（UI线程）中绘图（View.onDraw）

5.Window Surface硬件加速，View的Layer Type为HW，在主线程（UI线程）中绘图（View.onDraw）

2011-12-20 Roger, UC

CanvasCanvasCanvasCanvas

• Android3.0+后有3种不同的Canvas类型：

– android.graphics.Canvas

• 通过Bitmap生成的Canvas

• 当View的设置为SW Layer时，View在onDraw中获得的 Canvas

– android.view.Surface$CompatibleCanvas

• 通过SurfaceHolder.lockCanvas获得的Canvas

• 当Window非硬件加速时，Window中的View在onDraw中获得的 Canvas

– android.view.GLES20RecordingCanvas （HW HW HW HW Accelerated!!!Accelerated!!!Accelerated!!!Accelerated!!!）

• 当Window硬件加速时，Window中的View在onDraw中获得的 Canvas（View的Layer Type为None或者HW）

– isHardwareAccelerated用于判断Canvas是否使用硬件加速

2011-12-20 Roger, UC

Benchmark

2011-12-20 Roger, UC

https://github.com/rogeryi/0xbench_2d_hw

0xbench_2d_hw0xbench_2d_hw0xbench_2d_hw0xbench_2d_hw

2011-12-20 Roger, UC

TestTestTestTest

• 对应渲染模式1～4– 2D (SV)

– 2D (HW)

– 2D (SW1)

– 2D (SW2)

• 测试项包括：

– Draw Canvas 填充整个Canvas

– Draw Circle2 圆形填充

– Draw Rect 矩形填充

– Draw Arc 弧形填充

– Draw Image 位图绘制

– Draw Text 文本绘制

2011-12-20 Roger, UC

Samsung Samsung Samsung Samsung Galaxy Tab Galaxy Tab Galaxy Tab Galaxy Tab 10.1 (3.2)10.1 (3.2)10.1 (3.2)10.1 (3.2)

Draw Circle2 Draw Circle2 Draw Circle2 Draw Circle2 (texture/gradi(texture/gradi(texture/gradi(texture/gradient/color)ent/color)ent/color)ent/color)

Draw Rect Draw Rect Draw Rect Draw Rect (texture/gradi(texture/gradi(texture/gradi(texture/gradient/color)ent/color)ent/color)ent/color)

Draw Arc Draw Arc Draw Arc Draw Arc (texture/gradi(texture/gradi(texture/gradi(texture/gradient/color)ent/color)ent/color)ent/color)

Draw Image Draw Image Draw Image Draw Image (w/o filter)(w/o filter)(w/o filter)(w/o filter)

Draw TextDraw TextDraw TextDraw Text

2D (HW) 25/24.6/24.5 27.1/24/28 22.3/24/27 34/34 5

2D (SW1) 52.3/31/38 19.5/7/10.2 15/15.6/18.2 10.6/22 12

2D (SW2) 26.9/21/22 15.1/7/8.5 12/13.6/15.4 9.6/16.6 11

2D (SV) 51.7/38/46.8 19/10.5/13.8 13.4/21/25.8 11/25 13.1

Draw Canvas Draw Canvas Draw Canvas Draw Canvas (texture/gra(texture/gra(texture/gra(texture/gradient/color)dient/color)dient/color)dient/color)

59.4/24/60

43.3/46/56

58.5/21/60

27.6/17/28

2011-12-20 Roger, UC

Nexus S Nexus S Nexus S Nexus S (4.0.3)(4.0.3)(4.0.3)(4.0.3)

Draw Circle2 Draw Circle2 Draw Circle2 Draw Circle2 (texture/gradie(texture/gradie(texture/gradie(texture/gradient/color)nt/color)nt/color)nt/color)

Draw Rect Draw Rect Draw Rect Draw Rect (texture/gradie(texture/gradie(texture/gradie(texture/gradient/color)nt/color)nt/color)nt/color)

Draw Arc Draw Arc Draw Arc Draw Arc (texture/gradi(texture/gradi(texture/gradi(texture/gradient/color)ent/color)ent/color)ent/color)

Draw Image Draw Image Draw Image Draw Image (w/o filter)(w/o filter)(w/o filter)(w/o filter)

Draw Draw Draw Draw TextTextTextText

2D (HW) 30/30.0/31.2 45/16/45.7 40.5/13/44 28/28 3.2

2D (SW1) 52.6/49.4/50 37/17.7/28.6 47.5/29.7/43 28.5/49.2 8.5

2D (SW2) 43.7/36.4/39 27.4/16.6/22 35.6/24/32.4 21.4/32.2 8

2D (SV) 50.5/51.6/50 33.3/23.4/32 46/35.5/47.8 35.5/55.6 9

Draw Canvas Draw Canvas Draw Canvas Draw Canvas (texture/gradient(texture/gradient(texture/gradient(texture/gradient/color)/color)/color)/color)

55.5/55.6/54.5

42/42/53.8

55.7/55.9/55.4

48.2/42.8/41.4

2011-12-20 Roger, UC

Basic ConclutionsBasic ConclutionsBasic ConclutionsBasic Conclutions

• 模式1总是比模式3要快，因为没有异步请求（invalidate/onDraw）的延迟

• 模式3总是比模式4要快，模式4多了一次位图拷贝

• 模式2（硬件加速）跟模式3（非硬件加速）相比，有些快，有些慢

• 在硬件加速时，drawXXX方法实际只是将绘图指令存储到一个内部的绘图指令序列中（DisplayList），实际的绘制发生在onDraw调用之后

• 硬件加速的位图拉伸/旋转/扭曲绘制更平滑，filter bitmap flag总是打开的

2011-12-20 Roger, UC

Cont.Cont.Cont.Cont.

• 硬件加速绘图主要的优势在于– 位图绘制，特别是带拉伸，旋转，扭曲– 图层混合

• 硬件加速绘图主要的劣势在于文本绘制

• 对于图形填充（贴图平铺/渐变/纯色）情况比较复杂，一般来说需要Alpha混合的话，硬件加速绘图会比较快

• 并且需要绘制的图形/位图越多，越复杂的场景，硬件加速的优势越明显

• 充分利用硬件加速的图层混合（开启View的HW Layer）是实现60fps的实时交互和动画的关键

2011-12-20 Roger, UC

Some TipsSome TipsSome TipsSome Tips

• 硬件加速绘图不是Silver Bullet，always profile your bottleneck

• 避免在UI线程或者渲染线程中进行IO和网络操作（使用Strict Mode进行检测）

• 避免频繁修改位图（Bitmap），图形（Shape），避免在绘图方法中创建画笔（Paint）和路径（Path），特别是处于硬件加速时

2011-12-20 Roger, UC

RenferenceRenferenceRenferenceRenference

• Android 3.0 Hardware Acceleration

• New Gingerbread API: StrictMode

• How about some Android graphics true facts?

• How about some Android graphics true facts? [More]

• Understanding Hardware Acceleration on Mobile Browsers

• Android 圖形系統 -- 設計與實做分析

The EndThe EndThe EndThe End

Thank you for your listeningYours Sincerely, Roger