8. Multimedia.pptx

8. Graphics and Multimedia 何宗键 hezongjian@ Basic Drawing Animation Multimedia Encoding and Decoding Open GL ES Agenda Android Drawing system is powered by both 2D and 3D graphics drawing system. 2D: Skia graphic library acquired by Google 3D: Open GL ES 1.1 The Drawing System of Android Application Java Canvas / View / Widget Open GL ES Skia Surface Android Graphic Architecture Complete 2D graphic library for drawing Text, Geometries, and Images. Used by Android and Chrome Open source under Apache 2.0 at /p/skia/ Vector Graphic Engine Skia Graphics scalable resolution independent no background cartoon-like inappropriate for photo-realistic images metafiles contain both raster and vector data More about Vector Graphic Engine View Inherit from the View class, override the onDraw method Can only be draw in main UI thread Low performance SurfaceView Inherit or use system built-in SurfaceView class can be used in multi-thread environments High performance Where to draw Game sometimes blocks the UI and cause ANR dialog Avoid blocking UI using thread drawing As we know, Android didn’t allow UI operation in different thread. Surface View allow us do this Surface view and Game Demo: use the surface view SurfaceView sv = (SurfaceView) findViewById(R.id.sv); holder = sv.getHolder(); new Thread(new MyThread()).start(); class MyThread implements Runnable{ public void run() { Canvas canvas = holder.lockCanvas(null);//获取画布 Paint mPaint = new Paint(); mPaint.setColor(Color.BLUE); canvas.drawColor(Color.RED); canvas.drawRect(new RectF(40,60,80,80), mPaint); holder.unlockCanvasAndPost(canvas);//解锁画布，提交画好的图像 } } Canvas: The class host the drawing APIs = HDC Paint: describe the colors and styles for the drawing = HPEN, HBRUSH Drawing primitives: Drawable : bitmaps or other things that can be draw Path, Rect, Text… Basic concept for drawing Draw an Android r