Distorted custom Navigation buttons on non-retina display (using stretchable image method) - objective-c

Question

I am adding custom navigation buttons to my navigation bars via the following code.
//Instance method in CustomNavButton Class
-(UIButton*)setupButtonWithImage:(UIImage*)image andFrame:(CGRect)frame
{
UIButton *button = [[[UIButton alloc]initWithFrame:frame]autorelease];
UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake((frame.size.width-20)/2, (frame.size.height-20)/2, 20, 20)];
imageView.image = image;
UIImage *buttonImageNormal = [UIImage imageNamed:#"customBtn_black"];
UIImage *stretchableButtonImageNormal = [buttonImageNormal
stretchableImageWithLeftCapWidth:12 topCapHeight:0];
button.titleLabel.font = [UIFont boldSystemFontOfSize:12];
[button setBackgroundImage:stretchableButtonImageNormal
forState:UIControlStateNormal];
[button setTitleShadowColor:[UIColor whiteColor] forState:UIControlStateNormal];
[button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
[button addSubview:imageView];
return button;
}
//Call CustomNavButton and add to Navbar
- (void)viewDidLoad
{
[super viewDidLoad];
//Add left invite friends button
CustomNavButton *leftButton = [[CustomNavButton alloc]initWithImage:[UIImage imageNamed:#"friends_1"] andFrame:CGRectMake(0, 0, 40, 32)];
[leftButton.customNavButton addTarget:self action:#selector(inviteButtonPressed) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *leftBarButton = [[UIBarButtonItem alloc]initWithCustomView:leftButton];
self.navigationItem.leftBarButtonItem = leftBarButton;
[leftButton release];
}
The navigation buttons appear fine on my iPhone (IOS5 with Retina Display)
However, the buttons look distorted on my simulator (or non-retina display)
How can I resolve this? How can I display the buttons properly even for non-retina displays?
Note that I have created the #2x buttons for this as well
EDIT:
It seems like the issue likes with the stretching of the image
UIImage *stretchableButtonImageNormal = [buttonImageNormal
stretchableImageWithLeftCapWidth:12 topCapHeight:0];
If I change the leftCapWidth value to 0, the buttons on the simulator looks better (but still bad).
But by doing this, it will cause my retina display button look a little distorted (seems like I can't win).
Can anyone advise if the problem does really lie here, and how I can alter the values so that it works well for both retina and non-retina displays?

Answer 1

Do you have two files? MyImage.png and MyImage#2x.png? It looks like the system is trying to resize the #2x file by scaling it down, which usually causes some jaggedness like this when it is simply scaled down.
MyImage.png should be half the size of MyImage#2x.png.

Answer 2

Your not setting the file format .png or whatever it is you have. And as Chris said you need two files regular and #2x.