Loading a resource to a mutable bitmap

问题:

I am loading a bitmap from a resource like so:

 Bitmap mBackground = BitmapFactory.decodeResource(res,R.drawable.image);

What I want to do is make some changes to the bitmap before It gets drawn to the main canvas in my draw method (As it would seem wasteful to repeat lots of drawing in my main loop when it isn't going to change). I am making the changes to the bitmap with the following:

Canvas c = new Canvas(mBackground);
c.drawARGB(...); // etc

So naturally I get an exception

java.lang.IllegalStateException: Immutable bitmap passed to Canvas constructor

So to avoid that I made a copy of the bitmap so that it is mutable

Bitmap mBackground = BitmapFactory.decodeResource(res,R.drawable.image).copy(Bitmap.Config.ARGB_8888, true);

Which avoid the problem however it sometimes causes OutOfMemoryExceptions, do know any better ways of achieving what I want?

回答1:

There are several ways to create a copy of it. This thread might help you: http://www.anddev.org/how_to_modify_the_image_file-t513.html

回答2:

Use decodeResource(Resources res, int id, BitmapFactory.Options opts) and specify inMutable in the options.

http://developer.android.com/reference/android/graphics/BitmapFactory.html

回答3:

You'd better use RapidDecoder.

import rapid.decoder.BitmapDecoder;

Bitmap mBackground = BitmapDecoder.from(res, R.drawable.image)
        .mutable().decode();

Works for API level 8.

回答4:

in case you need to handle all API levels, check out this post:

https://stackoverflow.com/a/16314940/878126