title: Unity build project game 2d to apk with huge size because textures
body: <p>I have a project unity game 2d. when i build it with 70 MB in apk, i think it too large with my game.</p>
  
  <p>I try to delete some pictures (textures for backgrounds of game) about 6MB in my folder Assets\Resources (because my game load resource dynamically base on current level). Then rebuild it to apk. And it get 30MB. I wonder about it.</p>
  
  <p>this is editor log when i build apk with 70MB</p>
  
  <pre><code>Textures      182.1 mb   95.7% 
  Meshes        0.0 kb     0.0% 
  Animations    0.0 kb     0.0% 
  Sounds        1.1 kb     0.0% 
  Shaders       42.5 kb    0.0% 
  Other Assets  594.9 kb   0.3% 
  Levels        485.3 kb   0.2% 
  Scripts       1.2 mb     0.6% 
  Included DLLs 5.1 mb     2.7% 
  File headers  791.0 kb   0.4% 
  Complete size 190.3 mb   100.0% 
  
  
  Used Assets, sorted by uncompressed size:
   21.3 mb     11.2% Assets/Atlas/MainUIAtlas.png
   16.0 mb     8.4% Assets/Atlas/SupportItems.png
   12.0 mb     6.3% Assets/Resources/Backgrounds/A.jpg
   12.0 mb     6.3% Assets/Resources/Backgrounds/B.jpg
   12.0 mb     6.3% Assets/Resources/Backgrounds/C.jpg
   12.0 mb     6.3% Assets/Resources/Backgrounds/D.jpg
   9.0 mb  4.7% Assets/Resources/Map/bg_map3.jpg
   9.0 mb  4.7% Assets/Resources/Map/bg_map2.jpg
   9.0 mb  4.7% Assets/Resources/Map/bg_map1.jpg
   9.0 mb  4.7% Assets/Resources/Map/bg_map4.jpg
   8.0 mb  4.2% Assets/Resources/MainMenu/BG1.png
   6.8 mb  3.5% Assets/Resources/MainMenu/BG2.png
   .....
   .....
  </code></pre>
  
  <p>I use NGUI for creating UI in Unity2d, so i have some atlas file.
  However, Assets/Atlas/MainUIAtlas.png is only 734KB when I see it in window. Why Unity compress it with 21.3MB?</p>
  
  <p>And Assets/Resources/Backgrounds/A.jpg is only 194KB, but Unity compress it with 12MB...so on. All the information is too large to compare to real size in window.</p>
  
  <p>I am new Unity, Please help me to explain and tell me how to resolve this issue.
  Thanks a lot.</p>