drawable(2、bitmap)

给出一个PNG资源导入，由RGB转灰度并显示的例子，代码如下：

public class GrayView extends View {

    private Bitmap bmp;

    public GrayView(Context context) {
        super(context);
        Resources res = getResources();
        bmp    = BitmapFactory.decodeResource(res, R.drawable.ic_launcher);//将ic_launcher则个资源生成一个bitmap对象
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        Bitmap output = Bitmap.createBitmap(bmp.getWidth(),
                bmp.getHeight(),
                Config.ARGB_8888);//定义一个与原始bitmap一样大小的bitmap对象

        for(int i = 0; i < bmp.getWidth(); i++){
            for(int j = 0; j < bmp.getHeight(); j++){

                int color     = bmp.getPixel(i, j);//获取某一坐标的像素值
                int red     = Color.red(color); //解析出R、G、B的值
                int green     = Color.green(color);
                int blue     = Color.blue(color);

                int tmp = (red + green + blue)/3; //转换成灰度值

                output.setPixel(i, j, Color.rgb(tmp,tmp,tmp)); //给相应坐标的像素点赋值R、G、B
            }
        }
        canvas.drawBitmap(output, 100, 100, null);//将该bitmap绘制在canvas上
    }
}