How to make texture readable for assetbundle

I want read pixels from texture which set to read/write enable. But I got non-readable exception. My texture is the skin of character which package to assetbundle. I knew make texture readable will increase memory.

I have try such solutions:

1. http://answers.unity3d.com/questions/639234/instantiating-texture2d-object-get-non-readable-er.html

2. /Unity/Editor/Data/Documentation/html/en/ScriptReference/BuildPipeline.BuildAssetBundle.html

But failed, is there any solution? Thank you very much for your suggestion.

Maktech(http://answers.unity3d.com/questions/1148901/saving-textures-as-readable-in-assetbundles.html) have encounter similar problem.