void OnPreprocessTexture()
{
var importer = (assetImporter as TextureImporter);
importer.textureType = TextureImporterType.GUI;
importer.compressionQuality = (int)TextureCompressionQuality.Best;
if (assetPath.EndsWith ("PVR.png")) {
importer.textureFormat = TextureImporterFormat.RGBA32;
}
}