original image
result
myImageView.image = [myImageView.image resizableImageWithCapInsets:UIEdgeInsetsMake(20.f, 12.f, 19.f, 19.f)];
For lower iOS version, use
[UIImage stretchableImageWithLeftCapWidth:15 topCapHeight:13];
Stretching an UIImage while preserving the corners
original image resultmyImageView.image = [myImageView.image resizableImageWithCapInsets:UIEdgeInsetsMake(20.f, 12.f, 19.f, 19.f)];
For lower iOS version, use
[UIImage stretchableImageWithLeftCapWidth:15 topCapHeight:13];