I understand that CGAffineTransformMakeRotation can rotate an image, and CGAffineTransformMakeTranslation translates an image. I also understand CGAffineTransformConcat can merge two transformations. However, I cannot seem to figure out a way to move an image on an arc using both of these. I understand this is more a mathematical question but does anyone have a reference they can point me to?
Edit:
[bezierPathWithArcCenter:radius:startAngle:endAngle:clockwise:]
did the trick.
Reference: http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIBezierPath_class/Reference/Reference.html#//apple_ref/occ/clm/UIBezierPath/bezierPathWithArcCenter:radius:startAngle:endAngle:clockwise:
Use a CAKeyframeAnimation with the path set instead of discreet values.
CAKeyframeAnimation *a = [CAKeyframeAnimation animationWithKeyPath:#"position"];
CGRect circleRect = CGRectMake(0,0,50,50);
a.duration = 2.0;
a.rotationMode = kCAAnimationRotateAuto;
a.path = [UIBezierPath bezierPathWithOvalInRect:circleRect].CGPath;
[imageView.layer addAnimation:a forKey:#"moveCircle"];
Rotate it about the center of the circle corresponding to the arc.
This will involve three steps:
1) Translate so that the center of your arc moves to the origin.
2) Rotate through the appropriate angle.
3) Reverse the translation from step 1.
Related
I have a simple rotation gesture implemented in my code, but the problem is when I rotate the image it goes off the screen/out of the view always to the right.
The image view that is being rotated center X gets off or increases (hence it going right off the screen out of the view).
I would like it to rotate around the current center, but it's changing for some reason. Any ideas what is causing this?
Code Below:
- (void)viewDidLoad
{
[super viewDidLoad];
CALayer *l = [self.viewCase layer];
[l setMasksToBounds:YES];
[l setCornerRadius:30.0];
self.imgUserPhoto.userInteractionEnabled = YES;
[self.imgUserPhoto setClipsToBounds:NO];
UIRotationGestureRecognizer *rotationRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:#selector(rotationDetected:)];
[self.view addGestureRecognizer:rotationRecognizer];
rotationRecognizer.delegate = self;
}
- (void)rotationDetected:(UIRotationGestureRecognizer *)rotationRecognizer
{
CGFloat angle = rotationRecognizer.rotation;
self.imageView.transform = CGAffineTransformRotate(self.imageView.transform, angle);
rotationRecognizer.rotation = 0.0;
}
You want to rotate the image around it's center, but that's not what it is actually happening. Rotation transforms take place around the origin. So what you have to do is to apply a translate transform first to map the origin to the center of the image, and then apply the rotation transform, like so:
self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, self.imageView.bounds.size.width/2, self.imageView.bounds.size.height/2);
Please note that after rotating you'll probably have to undo the translate transform in order to correctly draw the image.
Hope this helps
Edit:
To quickly answer your question, what you have to do to undo the Translate Transform is to subtract the same difference you add to it in the first place, for example:
// The next line will add a translate transform
self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, 10, 10);
self.imageView.transform = CGAffineTransformRotate(self.imageView.transform, radians);
// The next line will undo the translate transform
self.imageView.transform = CGAffineTransformTranslate(self.imageView.transform, -10, -10);
However, after creating this quick project I realized that when you apply a rotation transform using UIKit (like the way you're apparently doing it) the rotation actually takes place around the center. It is only when using CoreGraphics that the rotation happens around the origin. So now I'm not sure why your image goes off the screen. Anyway, take a look at the project and see if any code there helps you.
Let me know if you have any more questions.
The 'Firefox' image is drawn using UIKit. The blue rect is drawn using CoreGraphics
You aren't rotating the image around its centre. You'll need correct this manually by translating it back to the correct position
Right now I'm populating a UIScrollView with a series of views. The views need to be warped to make the UIScrollView appear like a carousel. In other words when the user scrolls it needs to be like a circle. I've never done anything quite like this before, but I'm assuming CoreAnimation is out of the question and OpenGL needs to be used. If this is possible with CoreAnimation or Quartz then I really just need a sample on how to warp the views and I can figure the rest out myself but I'm not familiar with OpenGL.
If you want to warp the views, you'll either need OpenGL or you could use Core Animation's CAShapLayer which allows you to specify a bezier path which can have this curve in it. But keep in mind that this curving you're seeing is likely just an optical illusion (though in your image above it looks like an actual curve). If you get enough rectangles with the correct y axis rotation in a row, I think you can come up with the effect you're looking for with straight Core Animation. I'm pretty sure that's how things are implemented in the Core Animation demos Apple provided a couple years ago. Here's a screenshot from the video from that presentation:
I messed around with the transform of a view's layer a little bit and came up with this:
- (IBAction)sliderDidChange:(id)sender
{
CGFloat value = [(UISlider*)sender value];
CGFloat xOff = value - 0.5;
CATransform3D trans = CATransform3DIdentity;
trans.m34 = 1.0f / -1000.0f;
trans = CATransform3DRotate(trans, degreesToRadians(xOff * -25.0f), 0.0f, 1.0f, 0.0f);
trans = CATransform3DTranslate(trans, 0.0f, 0.0f, 900.0f * fabs(xOff));
[[frameView layer] setTransform:trans];
CGPoint center= [frameView center];
[frameView setCenter:CGPointMake(1024.0 * value, center.y)];
}
I threw together a demo project that shows how the rotation works in response to a slider. It doesn't use a scroll view so you would have to adapt it, but I think you can track the current scroll offset and apply the transform accordingly. Not sure if it will help but there it is.
In my experience, it is a bit tricky to get the values right. The way to give a view perspective is by manipulating it's layer transform. I have used the following method to achieve the transfor for a similar effect:
-(CATransform3D)makeTransformForAngle:(CGFloat)angle from:(CATransform3D)start{
CATransform3D transform = start;
// the following two lines are the key to achieve the perspective effect
CATransform3D persp = CATransform3DIdentity;
persp.m34 = 1.0 / -1000;
transform = CATransform3DConcat(transform, persp);
transform = CATransform3DRotate(transform,angle, 0.0, 1.0, 0.0);
return transform;
}
This was done to create a "flip page" animation, so you may need to adapt. To use it, do the following:
flip_page.layer.transform = [self makeTransformForAngle:angle from:CATransform3DIdentity];
where flip_page is a UIView. Cheers!
I have a a menu that is a CALayer that will slide across the screen to a given point. I want the effect where the menu will go a little past the point, then a little before the point, and then land on the point. I can move the menu by applying a transform, but I was hoping to get this bouncing effect to work. I was looking into CAKeyframeAnimation, but I'm having trouble locating an example/tutorial. I've looked at the CA Programming Guide but haven't really found anything. Any links or help would be great. Thanks.
I released some code a while ago that does just what you're looking for. Basically, you need to generate your own CGPathRef containing all of the points you want the layer to hit, and use that path for the path attribute of the CAKeyframeAnimation. The code will look something like this:
CGPoint path[3] = {
FTAnimationOutOfViewCenterPoint(enclosingView.bounds, view.frame, view.center, direction),
[self overshootPointFor:view.center withDirection:direction threshold:(overshootThreshold_ * 1.15)],
view.center
};
CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:#"position"];
CGMutablePathRef thePath = CGPathCreateMutable();
CGPathAddLines(thePath, NULL, path, 3);
animation.path = thePath;
CGPathRelease(thePath);
The whole method is here.
i am trying to implement a graph which a uiview draws. There are 3 UIViews to animate a left/right slide. The problem is, that i can't cancel the UIView animation. So I replaced the UIViews by CALayer. Now, the question is if CALayer is appicable for this? Is it normal to draw on a CALayer like this? And why is a CALayer so slow when I manipulate the frame properties.
CGRect frame = curve.frame;
frame.origin.x -= diffX;
[curve setFrame:frame];
Is there a alternativ?
P.S. I am a german guy. Sorry for mistakes.
I got the animation with CATransaction, but now I will animate a x move with CABasicAnimation. That's no problem expect that the position of the layer go back to the previous x.
CABasicAnimation *theAnimation;
theAnimation = [CABasicAnimation animationWithKeyPath:#"position"];
theAnimation.delegate = self;
theAnimation.duration = 1.0;
theAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
CGPoint position = [[curves objectAtIndex:i]position];
position.x = [[curves objectAtIndex:i]position].x - diffX;
[theAnimation setToValue:[NSValue valueWithCGPoint:position]];
[[curves objectAtIndex:i] addAnimation:theAnimation forKey:[NSString stringWithFormat: #"translate.x.%d", index]];
The position changes the position (e.g. xStart = 100, xEnd = 200), but when the animation ends the layer goes back to the beginning x (e.g. x = 100).
Is that normal? How can I solve this problem, that the end position doesn't change anymore?
I tried to changed the removeOnComplete property but that didn't effect.
Hope for help.
Markus
Not sure what you mean by 'slow', but setting the frame of a CALayer in this way uses 'implicit animation'. That is, it will animated the transition from the old frame to the new frame. You can turn this off:
[CATransaction begin];
[CATransaction setValue: (id) kCFBooleanTrue forKey: kCATransactionDisableActions];
[curve setFrame:frame];
[CATransaction commit];
However, this is usually considered an advantage of CALayer. You way want to just use UIViews here, which will not, by default, animate transitions such as this.
Instead of setting the destination position in theAnimation, just set the position property of the thing you want to move.
When you addAnimation:theAnimation, you're setting the "visual style" of any changes to the keyPath property you specified.
When you change the position of the object that the animation is attached to, say from (0,0) to (500,500), CoreAnimation will animate the change for you. The theAnimation object doesn't need the start and end positions, since the underlying object has them.
I'm fairly new to Quartz 2D.
Imagine the following scenario:
You have a circle-shaped mini map view.
I'm drawing triangle (the arc isn't important right now) on top of the map. This shape represents the visible area.
I need to have the triangle shape rotate along the mini map as the user changes orientation.
Currently this how the path is being drawn:
CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
CGPath visibleAreaPath = CGPathCreateMutable();
CGPathMoveToPoint(visibleAreaPath, &transform, miniMapCenter.x, miniMapCenter.y);
CGPathAddLineToPoint(visibleAreaPath, &transform, 18.0, 8.0);
CGPathAddLineToPoint(visibleAreaPath, &transform, 66.0, 8.0);
CGPathCloseSubpath(visibleAreaPath);
I then draw the path using a CAShapeLayer like so:
CALayer *rootLayer = [visibleAreaView layer];
visibleAreaShape = [CAShapeLayer layer];
[visibleAreaShape setFillColor:[UIColor colorWithHue:0.584 saturation:0.8 brightness:0.9 alpha:0.6].CGColor];
[visibleAreaShape setFillRule:kCAFillRuleNonZero];
[visibleAreaShape setAnchorPoint:CGPointMake(0.5, 0.5)];
[rootLayer addSublayer:visibleAreaShape];
[visibleAreaShape setPath:visibleAreaPath];
The path is being rotated, but not based on a given origin.
Keep in mind that setting the layer's anchor point doesn't help me since what I want is to rotate the path (ultimately I wouldn't even need to display it, since I will be using it to determine which points are visible on the mini map).
Any ideas on how to accomplish this?
Thank you.
I would suggest you store the points in polar form and convert to a path when needed. It's very easy to rotate in polar coordinates (simply change the theta value).