Android中Bitmap, Drawable, Byte,ID之间的转化

1 . Bitmap 转化为 byte

ByteArrayOutputStream out = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
byte[] array= out.toByteArray();

2 . byte转化为bitmap

Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

3 . bitmap转化为Drawable

Drawable drawable = new FastBitmapDrawable(bitmap);

4 . Drawable转化为bitmap

a. BitmapDrawable, FastBitmapDrawable直接用getBitmap
b. 其他类型的Drawable用Canvas画到一个bitmap上

   Canvas canvas = new Canvas(bitmap)
      drawable.draw(canvas)

5 . id转化graphic.drawable

 Drawabledrawable=activity.getResources().getDrawable(R.drawable.icon);

6 . id转化成Bitmap

Bitmap bitmap = BitmapFactory. decodeResource (Resources   res, int id)