Fix for centering thumb image when rotating UISlider 90 degrees to a vertical orientation

gistfile1.m

/*
	UISlider controls can be rotated to a vertical orientation with this setting:

	layer.transform.rotation.z = 1.570795 (type = String)

	in IB under User Defined Runtime Attibutes for the UISlider.

	However, this makes it visually obvious that iOS does not draw the thumb image 
	over the center of the slider track, it is actually offset 1 point up (when horizontal).

	The following code fixes that.
*/


- (void)viewDidAppear:(BOOL)animated {
	[super viewDidAppear:animated];

	[myVerticalSlider setThumbImage:[self offsetThumbImage:[myVerticalSlider thumbImageForState:UIControlStateNormal]] forState:UIControlStateNormal];
	[myVerticalSlider setThumbImage:[self offsetThumbImage:[myVerticalSlider thumbImageForState:UIControlStateHighlighted]] forState:UIControlStateHighlighted];
}


- (UIImage*)offsetThumbImage:(UIImage*)image {
	CGRect imageRect = CGRectMake(0, 0, image.size.width, image.size.height);
	UIGraphicsBeginImageContextWithOptions(imageRect.size, FALSE, 0.0);
	[image drawInRect:CGRectMake(0, 1, image.size.width, image.size.height)];
	image = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	return image;
}