Trouver objet le plus proche de CGPoint
Question
I ai quatre UIViews sur un UIScrollView (écran divisé en quartiles)
Sur les quartiles, j'ai quelques objets (UIImageViews), sur chaque quartile.
Lorsque l'utilisateur appuie sur l'écran, je veux trouver l'objet le plus proche de la? CGPoint donnée
Toutes les idées?
I ai l'CGPoint et le cadre (CGRect) des objets au sein de chaque quartile.
Mise à jour:
(source: skitch.com )
Red Pins sont UIImageViews.
// UIScrollView
NSLog(@" UIScrollView: %@", self);
// Here's the tap on the Window in UIScrollView's coordinates
NSLog(@"TapPoint: %3.2f, %3.2f", tapLocation.x, tapLocation.y);
// Find Distance between tap and objects
NSArray *arrayOfCGRrectObjects = [self subviews];
NSEnumerator *enumerator = [arrayOfCGRrectObjects objectEnumerator];
for (UIView *tilesOnScrollView in enumerator) {
// each tile may have 0 or more images
for ( UIView *subview in tilesOnScrollView.subviews ) {
// Is this an UIImageView?
if ( [NSStringFromClass([subview class]) isEqualToString:@"UIImageView"]) {
// Yes, here are the UIImageView details (subView)
NSLog(@"%@", subview);
// Convert CGPoint of UIImageView to CGPoint of UIScrollView for comparison...
// First, Convert CGPoint from UIScrollView to UIImageView's coordinate system for reference
CGPoint found = [subview convertPoint:tapLocation fromView:self];
NSLog(@"Converted Point from ScrollView: %3.2f, %3.2f", found.x, found.y);
// Second, Convert CGPoint from UIScrollView to Window's coordinate system for reference
found = [subview convertPoint:subview.frame.origin toView:nil];
NSLog(@"Converted Point in Window: %3.2f, %3.2f", found.x, found.y);
// Finally, use the object's CGPoint in UIScrollView's coordinates for comparison
found = [subview convertPoint:subview.frame.origin toView:self]; // self is UIScrollView (see above)
NSLog(@"Converted Point: %3.2f, %3.2f", found.x, found.y);
// Determine tap CGPoint in UIImageView's coordinate system
CGPoint localPoint = [touch locationInView:subview];
NSLog(@"LocateInView: %3.2f, %3.2f",localPoint.x, localPoint.y );
//Kalle's code
CGRect newRect = CGRectMake(found.x, found.y, 32, 39);
NSLog(@"Kalle's Distance: %3.2f",[self distanceBetweenRect:newRect andPoint:tapLocation]);
}
Console de débogage
Voici le problème. Chaque tuile est 256x256. La première CGPoint de UIImageView converti en système de coordonnées UIScrollView (53,25, 399,36) devrait être mort sur la tapPoint (30331). Pourquoi la différence ?? L'autre point à la droite du point taraudé calcule plus proche (distance sage) ??
<CALayer: 0x706a690>>
[207] TapPoint: 30.00, 331.00
[207] <UIImageView: 0x7073db0; frame = (26.624 71.68; 32 39); opaque = NO; userInteractionEnabled = NO; tag = 55; layer = <CALayer: 0x70747d0>>
[207] Converted Point from ScrollView: 3.38, 3.32
[207] Converted Point in Window: 53.25, 463.36
[207] Converted Point: 53.25, 399.36 *** Looks way off!
[207] LocateInView: 3.38, 3.32
[207] Kalle's Distance: 72.20 **** THIS IS THE TAPPED POINT
[207] <UIImageView: 0x7074fb0; frame = (41.984 43.008; 32 39); opaque = NO; userInteractionEnabled = NO; tag = 55; layer = <CALayer: 0x7074fe0>>
[207] Converted Point from ScrollView: -11.98, 31.99
[207] Converted Point in Window: 83.97, 406.02
[207] Converted Point: 83.97, 342.02
[207] LocateInView: -11.98, 31.99
207] Kalle's Distance: 55.08 ***** BUT THIS ONE's CLOSER??????
La solution
La méthode suivante devrait faire l'affaire. Si vous voyez quelque chose de bizarre dans ce ne hésitez pas à le signaler.
- (CGFloat)distanceBetweenRect:(CGRect)rect andPoint:(CGPoint)point
{
// first of all, we check if point is inside rect. If it is, distance is zero
if (CGRectContainsPoint(rect, point)) return 0.f;
// next we see which point in rect is closest to point
CGPoint closest = rect.origin;
if (rect.origin.x + rect.size.width < point.x)
closest.x += rect.size.width; // point is far right of us
else if (point.x > rect.origin.x)
closest.x = point.x; // point above or below us
if (rect.origin.y + rect.size.height < point.y)
closest.y += rect.size.height; // point is far below us
else if (point.y > rect.origin.y)
closest.y = point.y; // point is straight left or right
// we've got a closest point; now pythagorean theorem
// distance^2 = [closest.x,y - closest.x,point.y]^2 + [closest.x,point.y - point.x,y]^2
// i.e. [closest.y-point.y]^2 + [closest.x-point.x]^2
CGFloat a = powf(closest.y-point.y, 2.f);
CGFloat b = powf(closest.x-point.x, 2.f);
return sqrtf(a + b);
}
sortie Exemple:
CGPoint p = CGPointMake(12,12);
CGRect a = CGRectMake(5,5,10,10);
CGRect b = CGRectMake(13,11,10,10);
CGRect c = CGRectMake(50,1,10,10);
NSLog(@"distance p->a: %f", [self distanceBetweenRect:a andPoint:p]);
// 2010-08-24 13:36:39.506 app[4388:207] distance p->a: 0.000000
NSLog(@"distance p->b: %f", [self distanceBetweenRect:b andPoint:p]);
// 2010-08-24 13:38:03.149 app[4388:207] distance p->b: 1.000000
NSLog(@"distance p->c: %f", [self distanceBetweenRect:c andPoint:p]);
// 2010-08-24 13:39:52.148 app[4388:207] distance p->c: 38.013157
Il pourrait y avoir plus d'une version optimisée là-bas, donc peut-être la peine de creuser plus.
Le procédé suivant détermine la distance entre deux Points Cg.
- (CGFloat)distanceBetweenPoint:(CGPoint)a andPoint:(CGPoint)b
{
CGFloat a2 = powf(a.x-b.x, 2.f);
CGFloat b2 = powf(a.y-b.y, 2.f);
return sqrtf(a2 + b2)
}
Mise à jour: fabsf enlevé (); -x ^ 2 est le même que x ^ 2, il est donc inutile.
Mise à jour 2:. Méthode distanceBetweenPoint:andPoint:
ajouté trop, pour être complet
Autres conseils
Si vous utilisez Swift, voici comment vous pouvez calculer la distance entre un CGPoint et un CGRect (par exemple un cadre de UIView)
private func distanceToRect(rect: CGRect, fromPoint point: CGPoint) -> CGFloat {
// if it's on the left then (rect.minX - point.x) > 0 and (point.x - rect.maxX) < 0
// if it's on the right then (rect.minX - point.x) < 0 and (point.x - rect.maxX) > 0
// if it's inside the rect then both of them < 0.
let dx = max(rect.minX - point.x, point.x - rect.maxX, 0)
// same as dx
let dy = max(rect.minY - point.y, point.y - rect.maxY, 0)
// if one of them == 0 then the distance is the other one.
if dx * dy == 0 {
return max(dx, dy)
} else {
// both are > 0 then the distance is the hypotenuse
return hypot(dx, dy)
}
}
Merci @cristian,
Voici la version Objective-C de votre réponse
- (CGFloat)distanceToRect:(CGRect)rect fromPoint:(CGPoint)point
{
CGFloat dx = MAX(0, MAX(CGRectGetMinX(rect) - point.x, point.x - CGRectGetMaxX(rect)));
CGFloat dy = MAX(0, MAX(CGRectGetMinY(rect) - point.y, point.y - CGRectGetMaxY(rect)));
if (dx * dy == 0)
{
return MAX(dx, dy);
}
else
{
return hypot(dx, dy);
}
}
Shorter @cristian réponse:
func distance(from rect: CGRect, to point: CGPoint) -> CGFloat {
let dx = max(rect.minX - point.x, point.x - rect.maxX, 0)
let dy = max(rect.minY - point.y, point.y - rect.maxY, 0)
return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
}
Personnellement, je mettre en œuvre cela comme une extension CGPoint:
extension CGPoint {
func distance(from rect: CGRect) -> CGFloat {
let dx = max(rect.minX - x, x - rect.maxX, 0)
let dy = max(rect.minY - y, y - rect.maxY, 0)
return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
}
}
Vous pouvez également mettre en œuvre comme une extension CGRect:
extension CGRect {
func distance(from point: CGPoint) -> CGFloat {
let dx = max(minX - point.x, point.x - maxX, 0)
let dy = max(minY - point.y, point.y - maxY, 0)
return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
}
}