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

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

6.id转化成Bitmap

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

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