hy
i want to make a little animation.the rotation works fine if the image is static.
but when i move my image view it will stretch the image. the image can be moved
whit out a problem if it's not rotated.
-(void)play
{
CGRect ship=image.frame;
ship.origin.x=ship.origin.x+move;
ship.origin.y=ship.origin.y+move2;
image.frame=ship;
}
-(void)rotate
{
int degre=180;
float radian=degre*(3.14/180);
image.transform =CGAffineTransformMakeRotation(radian);
}
When using the transform property you are not allowed to change the position by changing the frame, you have to use the center property.
So this should help:
-(void)play
{
image.center=CGPointMake(image.center.x + move, image.center.y + move2);
}
Related
Hello everyone I am trying to zoom in a out a uiimageview using animation as i am scrolling down a uiscrollview. Please note its not about making a uiimageview zoom in and out in a uiscrollview.
I am able to detect how much i am scrolling down :
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
}
I need to zoom out the image depending( the scroll factor) how much i am scrolling down. Any idea how this can be done?
I suggesting changing the transform property of the image you are trying to scale
- (void)scrollViewDidScroll:(UIScrollView*)scrollView{
// this is just a demo method on how to compute the scale factor based on the current contentOffset
float scale = 1.0f + fabsf(scrollView.contentOffset.y) / scrollView.frame.size.height;
//Cap the scaling between zero and 1
scale = MAX(0.0f, scale);
// Set the scale to the imageView
imageView.transform = CGAffineTransformMakeScale(scale, scale);
}
If you also need the scrollview to go to the top one the imageview has been zoomed out, then you will need to adjust the frame of the scrollview and imageview.
Maybe you can tell us more about your desired effect.
Here's a Swift version of Andrei's answer. I am also exiting early if the user is swiping up (scrolling down), because I only wanted to show the zoom effect when they were pulling down on the table view.
// Exit early if swiping up (scrolling down)
if scrollView.contentOffset.y > 0 { return }
// this is just a demo method on how to compute the scale factor based on the current contentOffset
var scale = 1.0 + fabs(scrollView.contentOffset.y) / scrollView.frame.size.height
//Cap the scaling between zero and 1
scale = max(0.0, scale)
// Set the scale to the imageView
self.imageView.transform = CGAffineTransformMakeScale(scale, scale)
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.
I have a UIView that I rotate with this code:
helpView.transform = CGAffineTransformMakeRotation(degreesToRadians( rotationAngle ));
Where degreeToRadians just is a macro to convert from degrees to radians.
This works fine as long as the view is visible, eg alpha = 1. When I hide it (alpha = 0, which I animate) it does not rotate any more. I guess this is a smart way for the devices to "save" on drawing time, but is there any way I can force it to be drawn even when alpha is 0? Otherwise I will have to rotate it before I show it again.
Any good ideas?
Thanks
Edit: This is the code I use to show/hide the view.
-(void)showHelp
{
bool helpAlpha = !helpView.alpha;
CGFloat newScale;
if (helpView.alpha) {
newScale = kHelpSmall;
helpView.transform = CGAffineTransformMakeScale(kHelpBig, kHelpBig);
} else {
newScale = kHelpBig;
helpView.transform = CGAffineTransformMakeScale(kHelpSmall, kHelpSmall);
}
[UIView animateWithDuration:(kAnimationTimeShort / 2) animations:^(void) {
[helpView setAlpha:helpAlpha];
helpView.transform = CGAffineTransformMakeScale(newScale, newScale);
}];
}
As you see I also scale it for a nicer effect. Works perfect when visible, does not rotate when alpha = 0. Rotation is done in another method, where I would prefer to keep it as I also rotate some other views there.
You are resetting the transform every time you use CGAffineTransformMake*. If you do this, you will get either a rotated transform or a scaled one. I am assuming the scaled one is after the rotated one and hence you aren't able to see the view rotated. If you need both the effects to remain, you will have to use CGAffineTransformRotate. So a scale and rotate will be
helpView.transform = CGAffineTransformMakeScale(kHelpSmall, kHelpSmall);
helpView.transform = CGAffineTransformRotate(helpView.transform, degreesToRadians(rotationAngle));
The order might vary.
Me again. I have a simple question. I have an UIImageView like the one shown below.
alt text http://img683.imageshack.us/img683/1999/volumen.png
That UIimageView is supposed to be the knob to control the volume of my iphone project. My question is, how to know the positions of bar on the UIImageView when it is rotated? Because the volume needs to be 0.5 when the little bar on the cercle is vertical.
I got a piece of code which is (in the touchMoved method):
float dx = locationT.x - imgVVolume.center.x;
float dy = locationT.y - imgVVolume.center.y;
CGFloat angleDif = 0.0f;
movedRotationAngle = atan2(dy,dx);
if (beganRotationAngle == 0.0) {
beganRotationAngle = movedRotationAngle;
initialTransform = imgVVolume.transform;
}
else {
angleDif = beganRotationAngle - movedRotationAngle;
CGAffineTransform newTrans = CGAffineTransformRotate(initialTransform, -angleDif);
imgVVolume.transform = newTrans;
}
Help please.
It depends on what input mechanism you want to use to control the rotation.
If the knob is to rotate based on a single finger touch dragging from side to side then you can create a UIPanGestureRecognizer and attach it to the knob UIImageView. The translationInView: method returns a CGPoint which is the amount of X and Y movement from the touch-down point. You can feed that into a formula like the one you post to get an angle of rotation. You'll want to keep track of delta from last position and also check for stop limits (like 0..360) to prevent over-rotation.
OTOH, if you're going to use two finger rotation then you'll want to use a UIRotationGestureRecognizer and look for the rotation value. Just feed that into a CGAffineTransformRotate and set it to the UIImageView transform. That takes care of all of the above for you. Again, you'll want to check for stop limits.