Getting location of section of sprite - ios

Question

I'm using IOS7's sprite kit and using NSSpriteNode with default anchor of (.5, .5) [center]. The sprite will be rotating around a lot, is there a way to get the location relative to the anchor point? Like, if I'm looking for the sprites top-center anchorpoint of (.5,1) or bottom-center (.5, 0)? This way I can always get the same location of a part of a sprite however it is rotated?
self.player = [SKSpriteNode spriteNodeWithImageNamed:#"ship.png"];
self.player.anchorPoint = CGPointMake(.5, 1);
CGPoint p = [self.player convertPoint:self.player.position toNode:self]];
NSLog(#"x=%f,y=%f", p.x, p.y);
self.player.anchorPoint = CGPointMake(.5, 0);
CGPoint p = [self.player convertPoint:self.player.position toNode:self]];
NSLog(#"x=%f,y=%f", p.x, p.y);
This ends up yielding the same point even though I'm changing my anchor point to be different parts. I know this is a bad idea to change the anchor point, but trying to give an idea of what I'm trying to do.
I'd like a method something like:
CGPoint imageTopLoc = [self.player getLocationUsingAnchorPoint:CGPointMake(.5, 1)];
CGPoint imageBottomLoc = [self.player getLocationUsingAnchorPoint:CGPointMake(.5, 0)];
// calculate vector of direction between of two points... (next)
Thanks,
Chris

Answer 1

This code returns the coordinates / touch point inside a node, regardless of the node's rotation. (It's based upon the SpriteKit Game template.)
Is that what you are looking for?
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
SKSpriteNode *ship = [SKSpriteNode spriteNodeWithImageNamed:#"Spaceship"];
ship.name = #"ship";
ship.position = CGPointMake(100, 100);
ship.zRotation = M_PI * 0.5;
[self addChild:ship];
}
return self;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
for (UITouch *touch in touches) {
CGPoint location = [touch locationInNode:self];
SKNode *ship = [self childNodeWithName:#"ship"];
CGPoint p = [self convertPoint:location toNode:ship];
NSLog(#"x=%f,y=%f", p.x, p.y);
}
}