title: Android background image memory usage
body: <p>The project I'm working on uses several "high resolution" backgrounds (note the quotes). Just to get into situation, one of them is a 640x935 1.19M PNG file. As far as I know, even if Android decompresses images into memory as raw data this should be:</p>
  
  <p>640 x 935 x 4bytes = 2.39M</p>
  
  <p>I'm having memory issues on my project which I cannot really understand and I hope someone can shed some light on this matter. I'll name two devices that I am developing in and some of the results.</p>
  
  <p>To make sure this wasn't a secondary problem I made an activity not load the background when first created and then, when the user presses a button, all it does is:</p>
  
  <pre><code>findViewById(R.id.completed_block_background).setBackgroundResource(R.drawable.blockbackgroundbottom1);
  </code></pre>
  
  <p>Then, using DDMS with "Update Heap" on the process (and first forcing GC to make sure this won't be a problem), I'm getting the following memory results:</p>
  
  <p>Nexus S: Going from 18M to 26M (8M difference) </p>
  
  <p>Galaxy Nexus: Going from 28M to 39M (11M difference)</p>
  
  <p>So, as you can see, putting that theorically 2.39M uncompressed image into the background actually increases 8M and 11M in memory usage. Can someone explain why is this and if there is any solution?</p>
  
  <p>The only solution I have been able to find is using bitmaps to halve resolution or to lower the channel format (so far this is what I have done, switched them to 565 RGB, but this makes some banding problems which I cannot accept).</p>
  
  <p>I would also accept, in case there's nothing that can be done, an explanation of why this is happening. Thanks in advance.</p>