image stretched when packing textures in large size

I was using UIToolkit from Prime31 and Texture Packer to pack a group of my textures. The image is 1024x2048 after packing, and it doesn’t display correctly in Unity3D. Actually it’s kinda like being stretched or something.

  1. It’s not the issue of the UIToolkit, for there’s no errors nor exceptions. And I didn’t change the script a thing.
  2. It might not be the issue of TexturePacker, for I’ve checked the published image in Mac Finder, and it’s okay.
  3. Things are not right when I’m checking the preview in Unity3D. The preview in Unity3D is Stretched. And the GUI in gameplay is stretched,too, as I described in the beginning. But I’ve set the image type as GUI. And I’ve tried to set the image’s size from 1024 to 4096. They all act not-normal.

My questions are,
Have you tried to pack images in large size like me? You have the same issue?
Unity3D cannot handle this size of texture? Kinda unbelievable.
I’m using Unity3D 3.5.

Thank you guys!

It seems that I set the format as 16bit or true color, rather than compressed, there will be no problem then.