内存与性能，哪个最好？

Question

I need to take an image, scale it, mask it, add a background in case some of it is transparent and then add an overlay image. To do this I've written the following:

Canvas canvas = new Canvas();
Bitmap mainImage = Bitmap.createScaledBitmap(((BitmapDrawable)d).getBitmap(), iconSize, iconSize, false);
Bitmap result = Bitmap.createBitmap(iconSize, iconSize, Bitmap.Config.ARGB_8888);

canvas.setBitmap(result);
Paint paint = new Paint();
paint.setFilterBitmap(false);

Bitmap mask = Bitmap.createScaledBitmap(BitmapFactory.decodeResource(context.res, context.mask_bg)
                    , iconSize, iconSize, false);
                        canvas.drawBitmap(mask, 0, 0, paint);
canvas.drawBitmap(mainImage, 0, 0, paint);

mask = Bitmap.createScaledBitmap(BitmapFactory.decodeResource(context.res, context.mask)
                    , iconSize, iconSize, false);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
canvas.drawBitmap(mask, 0, 0, paint);

mask = Bitmap.createScaledBitmap(BitmapFactory.decodeResource(context.res, context.mask_frame)
                    , iconSize, iconSize, false);
paint.setXfermode(null);
canvas.drawBitmap(mask, 0, 0, paint);

Now this operation is going to happen alot in my application. And my application always has a service running (which is the context in this case). I don't know too much about performance when it comes to images and I know they use up to 4 times their actual size in space but this seems like a waste to me recreating the same objects over and over. Plus the main need for my app is performance over size.

So I'm wondering is it better to keep the bitmaps being generated each time in the service so they're only created once (only the mainImage bitmap will change each time) or even as a drawable create the bitmap from that?

Answer 1

Never conserve a drawable outside of the activity/fragment where it is displayed.
It can very easily create memory leaks : the drawable keep a reference to its activity, so the garbage collector can not destroy it, even if it has been destroyed and recreated since.
Use bitmaps instead.