Aug 8, 2015

Re-using Bitmaps

In modern mobile applications, Bitmaps can account for a large amount of memory churn. Constantly loading thumbnails, user icons, and Emoji sets can provide your users with a steady stream of media, but it can also contribute to some HUGE pauses for garbage collection. 

In this video Colt McAnlis, and for temporally allocated bitmaps, there’s a handy trick that you absolutely should be using to escape these performance problems: Re-using bitmaps.

Every time you allocate a bitmap, you have to incur some overhead to allocate the objects from the heap, which is less than ideal if you’ve got a lot of bitmaps. Rather than banging on the heap for new objects each time, you can instead, reuse the memory that an existing bitmap has created, and load your image there.

The end result? Less memory churn from bitmaps.

Pre-scaling Bitmaps

For media rich applications, BITMAPS are everywhere. But these high-resolution images can cause a horde of performance problems if the size of the image in memory is larger than the size you’re displaying it on screen. As such one of the most important things you can do to alleviate memory pressure in your app, is resizing your bitmaps.

Rather than writing all your own image resizing code, Android has a set of APIs which can do all this work for you. But the trick is, knowing which one to use?

For example, inSampleSize is the fastest way to down-scale your image; But you can only make it smaller by some factor of your image. createScaledBitmap is a great API, but requires an extra memory allocation to get it done.

Thankfully, Colt McAnlis covers all these topics (and more) in this video, helping you reduce your memory footprint, and get some smaller images.

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