I have two images.
One image is rectangle
second is triangle
i want to rotate tringle image from the center point of rectangle image using one finger or touch event.
Well, the math for this will get decently complex if you wish for the image to rotate in a circle of any size around the rectangles center point, but a good start would be to define the anchor point of the triangle image view, e.x.
#import <QuartzCore/QuartzCore.h>
#define degreesToRadians(x) (M_PI * x / 180.0)
[[triangleImageView layer] setAnchorPoint:CGPointMake:(0.5,0.0)];
[UIView animateWithDuration:1.0 animations:^{
[triangleImageView setTransform:CGAffineTransformMakeRotation(degreesToRadians(90))];
}];
Finally i found that i have to use [view.layer setAnchorPoint:CGPointMake(0.5, 0.5)]
and it solve my problem.
Related
Using a UIPanGestureRecognizer, I'm allowing the user to drag a UIView. What I now want to accomplish is getting the view to adjust its rotation around a specified point DURING dragging.
Examples of this can be found in the Tinder App (when dragging a portrait the images rotate slightly) or in the Path App (when dragging a friends popup up or down it rotates to the side grabbed on).
I must admit that I have very little experience working with UIPanGestureRecognizer, but I assume that it won't affect the answer.
Nevertheless one solution could be to create a timer and make it run while the UIView is being dragged, the timer action would then make sure to update the rotation of the UIView properly and as often as possible.
Another solution could be to subclass UIView and overwrite the drag-function (I do not know what it is called) and simply make it self adjust its rotation if any pivot point is given.
Do the rotation in the following method
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
self.yourView.transform = CGAffineTransformMakeRotation(CGFloat angle);
}
Use CATransform3D
Add
#define DEGREES_TO_RADIANS(d) (d * M_PI / 180)
in .pch file
CATransform3D myTransform = CATransform3DIdentity;
myTransform.m34 = 1.0 / -500;
myTransform = CATransform3DRotate(myTransform, DEGREES_TO_RADIANS(90), 0.0f, 0.0f, 1.0f);
myView.layer.transform = myTransform;
you can go on changing the angle here DEGREES_TO_RADIANS(90) Hope this will help you
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
I have a custom UIImageView, I can drag it around screen by making a translation with (xDif and yDif is the amount fingers moved):
CGAffineTransform translate = CGAffineTransformMakeTranslation(xDif, yDif);
[self setTransform: CGAffineTransformConcat([self transform], translate)];
Let's say I moved the ImageView for 50px in both x and y directions. I then try to rotate the ImageView (via gesture recognizer) with:
CGAffineTransform transform = CGAffineTransformMakeRotation([recognizer rotation]);
myImageView.transform = transform;
What happens is the ImageView suddenly moves to where the ImageView was originally located (before the translation - not from the moved position + 50px in both directions).
(It seems that no matter how I translate the view, the self.center of the ImageView subclass stays the same - where it was originally laid in IB).
Another problem is, if I rotate the ImageView by 30 deg, and then try to rotate it a bit more, it will again start from the original position (angle = 0) and go from there, why wouldn't it start from the angle 30 deg and not 0.
You are overwriting the earlier transform. To add to the current transform, you should do this –
myImageView.transform = CGAffineTransformRotate(myImageView.transform, recognizer.rotation);
Since you're changing the transform property in a serial order, you should use CGAffineTransformRotate, CGAffineTransformTranslate and CGAffineTransformScale instead so that you add to the original transform and not create a new one.
By default, a UIImageView will rotate only about its center. How do I get it to rotate about any other point in the image?
One way of doing this is by changing the anchorPoint of the UIImageView's underlying layer and rotating about that. You can change the point of rotation using something like the following:
imageView.layer.anchorPoint = CGPointMake(0.25, 0.25);
anchorPoint is defined in terms of relative coordinates within the layer. That is, (0,0) is the upper-left of the layer (on the iPhone, where UIView layers have flipped Y coordinates) and (1,1) is the lower-right.
Moving the anchorPoint may move your image, so you might need to adjust its position afterwards.
To rotate the image's layer about that new anchor point, you can change the CATransform3D struct for the layer using something like the following:
CATransform3D rotatedTransform = imageView.layer.transform;
rotatedTransform = CATransform3DRotate(rotatedTransform, 60.0 * M_PI / 180.0, 0.0f, 0.0f, 1.0f);
imageView.layer.transform = rotatedTransform;
This example does an incremental rotation of 60 degrees about the anchor point.
All changes to a layer are animated by default. You can disable this animation by enclosing your changes to these properties in a CATransaction like the following:
[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
// Code for changes here
[CATransaction commit];
Sorry if this is obvious or covered elsewhere, but i've been googling all day and haven't found a solution that actually worked.
My problem is as follows: I am currently drawing an image in a full screen UIView, for examples sake we'll say the image is in the bottom right corner of the UIView. I'd like to do a rotation transform(CGAffineTransformMakeRotation) at the center of that image, however, by default the rotation command rotates around the center of the UIView it self. As a result, my image moves around the screen when i rotate instead of it staying in place and rotating around its own center.
From what i've gathered, i need to translate my context so that the origin(center of the UIView) is at the center of my image, Rotate, and then restore the context by translating back to the original spot.
The following is the closest thing i've gotten to work, but the problem is that while the image is rotating, it moves downward while it's rotating. I think this is caused by animation tweening the 1st step translate and 3rd step translate instead of just realizing that the beginning and end point on the translates would be the same...
// Before this i'd make a call to a function that draws a path to a passed in context
CGAffineTransform inverseTranslation = CGAffineTransformMakeTranslation( transX, transY );
CGAffineTransform translation = CGAffineTransformMakeTranslation( -transX, -transY );
CGAffineTransform rot = CGAffineTransformMakeRotation( 3.14 );
CGAffineTransform final = CGAffineTransformConcat( CGAffineTransformConcat( inverseTranslation, rot ), translation );
// Then i apply the transformation animation like normal using self.transform = final etc etc
I've also tried stuff like CGContextTranslateCTM and CGContextSaveGState/UIGraphicsPushContext, but these seem to have little effect.
I've been fighting with this for days and my current solution seems close, but i have no clue how to get rid of that translating tweening. Does anyone have a solution for this or a better way to go about this?
[update]
For the time being i'm drawing my image centered at the UIview's center and then setting the UIView.center property to the origin i'd like to rotate and then doing the rotate command. Seems like a bit of a hack, but until i can get the real translates working it's my only choice.
Thanks!
duncanwilcox' answer is the right one, but he left out the part where you change the anchor of the view's layer to the point you want to rotate around.
CGSize sz = theview.bounds.size;
// Anchorpoint coords are between 0.0 and 1.0
theview.layer.anchorPoint = CGPointMake(rotPoint.x/sz.width, rotPoint.y/sz.height);
[UIView beginAnimations:#"rotate" context:nil];
theview.transform = CGAffineTransformMakeRotation( 45. / 180. * M_PI );
[UIView commitAnimations];
This is documented here: http://developer.apple.com/documentation/Cocoa/Conceptual/CoreAnimation_guide/Articles/Layers.html
This is also an option: a simple change of basis ;-)
CGAffineTransform transform = CGAffineTransformMakeTranslation(x, y);
transform = CGAffineTransformRotate(transform, angle);
transform = CGAffineTransformTranslate(transform,-x,-y);
where (x,y) is the rotation center you like
Rotation happens around the anchorPoint of the view's layer. The default for the anchorPoint is the center (0.5, 0.5), so the rotation alone without the translations should suffice.
Did a quick test and this works for me:
[UIView beginAnimations:#"rotate" context:nil];
self.transform = CGAffineTransformMakeRotation( 45. / 180. * 3.14 );
[UIView commitAnimations];
If you don't want an animation to occur, but just set the new rotation, you can use this:
CGFloat newRotation = 3.14f
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.0]; // no tweening
CGAffineTransform transform = CGAffineTransformMakeRotation(newRotation);
self.transform = transform;
[UIView commitAnimations];
The rotation should indeed take place around the center of the UIView. Setting the animationDuration to zero garantees no tweening should happen.
Be sure though you don't do this 60 times a second. It's very tempting to create game like animations with these tools. These kind of animations aren't exactly meant for a frame to frame based, "lots of sprites flying everywhere" game.
For that - and I've been down that road - the only way to go, is OpenGL.