1. Android

2. Android Drawing on Android: Canvas vs. OpenGL Bitmap vs. Texture
NDK: Native Development Kit

3. Canvas Canvas.drawLine(), drawRect(), etc. Canvas.setMatrix(m);
Canvas.setBitmap(bmp);
View.onDraw(Canvas);

4. Bitmap Bitmap.createBitmap(width, height, config);
BitmapFactory.decodeFile(file, options);
With or without alpha channel (transparency).

5. View: events & invalidation
onDraw(canvas)
invalidate() → onDraw()
onTouchEvent() → invalidate()

6. PixelFormat RGB_565 (2 bytes / pixel) ARGB_8888 (4 bytes / pixel)
Bitmap.Config
getWindow().setFormat()
PixelFormat.RGBA_8888

7. Dithering

8. Canvas Not hardware accelerated (CPU) Uses Bitmap for images
Rendering in UI thread, invalidate() model
Fast scrolling
Slow zooming, rotation, 3d projections

9. OpenGL ES Hardware accelerated (GPU) Uses Textures for images
Rendering in separate thread (not UI thread)
Fast zooming, 3d projections
Fragmentation, complexity, hard to debug

10. Bitmap vs. Texture Bitmaps: use Java heap, limited to 24MB.
4bytes/pixel (ARGB)
Textures:
use native memory, limited only by total RAM.
can use 3bytes/pixel (RGB).
support pixmaps.
may use fast GPU memory.

11. Native Development Kit (NDK)

12. Native Development Kit (NDK)
JNI: Java Native Interface
C, C++
GCC cross compiler
STL, exceptions, RTTI
arm-linux-gnueabi, RISC, little endian, 32bit
Thumb or ARM instructions
Without hardware floating point

13. Why use NDK
Performance critical code, e.g. FFT, game physics library, image/sound processing.
Performance: avoid Java object creation and GC, e.g. filesystem scan.
Use existing non-Java code/libraries (e.g. Python interpreter in C).

14. Java Native Interface (JNI)
class Hello {
public native static int sum(int[] data);
static {
System.loadLibrary(“hello”); }

15. JNI
C++ code
JNI book

16. Stable APIs C library Math library Zlib OpenGL ES 1.x & 2.0 OpenSL ES
Android Log
Bitmap interface (jnigraphics)
Android native application API

17. NDK and Market
Native code compiled for multiple architectures in a single APK.
Market does filtering based on architectures available in APK and on platform version.

18. Thank you