Bitmap回收

使用时加裁，用完回收

Bitmap icon = BitmapFactory.decodeResource(res, a);
Bitmap largeScaledIcon = Bitmap.createScaledBitmap(icon, newWidth, newHeight, false);
icon.recycle();
saveCanvas.drawBitmap(largeScaledIcon, newPositionX, newPositionY, paint);
largeScaledIcon.recycle();