I'm implementing a basic speedometer using an image and rotating it. However, when I set the initial rotation (at something like 240 degrees, converted to radians) It rotates the image and makes it much smaller than it otherwise would be. Some values make the image disappear entirely. (like M_PI_4)
the slider goes from 0-360 for testing.
the following code is called on viewDidLoad, and when the slider value is changed.
-(void) updatePointer
{
double progress = testSlider.value;
progress += pointerStart
CGAffineTransform rotate = CGAffineTransformMakeRotation((progress*M_PI)/180);
[pointerImageView setTransform:rotate];
}
EDIT: Probably important to note that once it gets set the first time, the scale remains the same. So, if I were to set pointerStart to 240, it would shrink, but moving the slider wouldn't change the scale (and it would rotate it as you'd suspect) Replacing "progress" with 240 in the transformation does the same thing. (shrinks it.)
I was able to resolve the issue for anybody who stumbles across this question. Apparently the image is not fully loaded/measured when viewDidLoad is called, so the matrix transforms that cgAffineTransform does actually altered the size of the image. Moving the update code to viewDidAppear fixed the problem.
Take the transform state of the view which you want to rotate and then apply the rotation transform to it.
CGAffineTransform trans = pointerImageView.transform;
pointerImageView.transform = CGAffineTransformRotate(trans, 240);
Related
I am trying to draw a simple straight line. For this, I am filling an UIImageView with some color with given width as, say 2 pixel and some length. Now user is provided with two UISliders out of which one is used to stretch the line and another slider to rotate. I use myImageView.frame to change the height and CGAffineTransform to rotate. It works fine until I change the rotation angle using slider. But once I rotate the imageview, The slider to stretch doesn't work properly.
I have searched and found that frames won't work after rotating using CGAffineTranfor.
Alternately bounds should work but that didn't work too.
Seeking help. Any brief code will help me.
Thanks in advance.
Give transformed bounds every time you apply a transform. This should work:
CGRect transformedBounds = CGRectApplyAffineTransform(myView.bounds, myView.transform);
I have a UIImageView that is set to move up and down the screen with the value of the accelerometer, using the following code:
ship.center = CGPointMake(ship.center.x, ship.center.y+shipPosition.y);
Where shipPosition is a CGPoint set in the accelerometerDidAccelerate method using:
shipPosition.y = acceleration.x*60;
Obviously this works fine, it is very simple. I run into trouble when I try to something equally simple, vary the rotation of the image depending on its acceleration. I do this using:
ship.transform = CGAffineTransformMakeRotation(shipPosition.y);
For some reason this causes a very strange thing to happen, in that the image snaps back to its origin every time the main method is called. I can see frames where the image moves to where it should be, but then instantly snaps back.
This problem only happens when I have the rotation line in, commented out it works fine. I have no idea what is going on here, I have done this many times for different apps and i never had such a problem. In fact I copied my code from a different app I created where it works fine.
EDIT:
What really confuses me is when I change the angle of the rotation from the acceleration to the position of the ship using:
ship.transform = CGAffineTransformMakeRotation(ship.center.y/10);
When I do this, the ship actually rotates based on the accelerometer but does not move, which is crazy because a changing ship.center.y means the position of the ship is changing, but it's not!!
You should set the transform of you view back to CGAffineTransformIdentity before you set his center coordinates or frame and after that apply the new transformation.
The frame property returns the transformed coordinates of a view if it is transformed and not the true (well actually the transformed are true) coordinates.
Quote from the docs:
Warning: If the transform property is not the identity transform, the value of this property is undefined and therefore should be ignored.
Update/Actual Answer:
Well the actual problem is
shipPosition.y = acceleration.x*60;
Since you set the y pos in accelerometerDidAccelerate.
The acceleration won't remember it's old value. So if you move your device it will get a peak and as you slow down it will decelerate again.
Your ship will be +/-60 at the highest acceleration speed but will be 0 when you stop moving your device and shipPosition.y will be 0.
CGAffineTransformMakeRotation expects angle in radians, not in degrees.
1 radian = M_PI / 180.0 degrees
I need to change the size of my images according to their distance from the center of the screen. If an image is closer to the middle, it should be given a scale of 1, and the further it is from the center, the nearer it's scale is to zero by some function.
Since the user is panning the screen, I need a way to change the images (UIViews) scale, but since this is not a very classic animation where I know a how to define an animation sequence exactly - mostly because of timing issues (due to system performance, I don't know how long the animation will last), I am going to need to simply change the scale in one step (no timed animations).
This way every frame the functiion gets called when panning, all images should update easily.
Is there a way to do that ?
You could directly apply a CGAffineTransform to your UIImageView. i,e:
CGAffineTransform trans = CGAffineTransformMakeScale(1.0,1.0);
imageView.transform = trans;
Of course you can change your values, and or use other CGAffineTransform's, this should get you on your way though.
Hope it helps !
hi all upto now i know making rectangle with the CGrectmake and this rect(frame) i am using as imageview frame like UIImageView *someImage=[[uiimageview alloc]initwithframe:someRect]; now i can add an image with the frame of someRect. my problem here is when the coordinates like
(rectangleFirstx-coordinate,tectangleFirstY-cordinate)=(10,10)
(rectangleLastx-cordinate,rectangleLasty-cordinate)=(17,7) this, how can i give frame to the uiimageview....This is like a inclined rectangle..can any one suggest me how to apply frame through the ios library for these type of coordinates..Thanks in advance..
Your example isn't very clear because a rectangle with opposite corners at (10,10) and (10,7) can be in any one of a myriad of different orientations, including one perfectly aligned along the x and y axis.
What you can certainly do is create a UIImageView of the desired size and location and then rotate it by using one of many techniques, including animation methods.
[UIImageView animateWithDuration:0.1 animations:^
{
your_UIImageView_here.transform = CGAffineTransformMakeRotation((M_PI/180.0) * degrees);
}];
You can hide the UIImageView until the rotation is done and then show it.
If your question is about how to use the coordinates you provided to arrive at an angle I'd suggest that more data is needed because it is impossible to pick one of the billions of possible rectangles with corners at those two points without more information. Once you have more data then it is pretty basic trigonometry to figure out the angle to feed into the rotation.
In an application showing chunks of text, I'm having the font size increase when the device is turned to a landscape orientation. I don't like how it does the whole animation and then suddenly jumps to the new size, so I'd like to animate the size change over the course of the rotation.
I read somewhere that throwing this change in a UIView animation block doesn't work because the font property is not animatable, so what are my options for doing this?
For my specific implementation I'm not simply scaling the UILabel/UITextView as-is; The bounds of the box is increasing more (proportionally) than the font-size, so there will be re-flow in the text. That's fine by me.
Edit: I would be fine with simply scaling the UITextView.
Also, I was considering "animating" it manually: I have a method that lays out my views and adjusts for font size. If I knew when the rotation was about to start, and the duration of the animation, I could time it so it renders an intermediate font size or two in the middle of the animation. Any help with getting those would be appreciated.
One option is to fade the old text out, change the font size, and fade it back in. The font property may not be animatable, but alpha is. Since alpha is a property of UIView, you can treat all your text-bearing views the same way: UILabel, UITextView, etc. It looks good, too.
If I knew when the rotation was about
to start, and the duration of the
animation...
Funny you should mention that. Just before the animation starts, your view controller will receive a willAnimateRotationToInterfaceOrientation:duration: message that gives you the exact information you need.
A way to proceed could be to:
Create a CAKeyframeAnimation
Define the scaling and rotation you want to achieve during that animation using a set of CATransform3D objects
Add these transforms to your keyframed animation
Send the addAnimation message to your label layer object: [[label layer] addAnimation];
Here would be a code sample assuming yourLabel is the UILabel you want to scale and rotate:
CAKeyframeAnimation *scale = [CAKeyframeAnimation animationWithKeyPath:#"transform"];
CATransform3D scaleUp = CATransform3DMakeScale(1.5, 1.5, 1); // Scale in x and y
CATransform3D rotationScaled = CATransform3DRotate (scaleUp, 90, 0, 0, 1); // Rotate the scaled font
[scale setValues:[NSArray arrayWithObjects:
[NSValue valueWithCATransform3D:CATransform3DIdentity],
[NSValue valueWithCATransform3D:rotationScaled],
nil]];
// set the duration
[scale setDuration: 1.0];
// animate your label layer
[[yourLabel layer] addAnimation:scale forKey:#"scaleText"];
This is typically how a text bouncing around would be animated for instance.
You could start this when the device starts rotating and retrieve the animation when it's done rotating so you can update your label with the proper scale/position.
You will need tuning to find the proper timing and rotation.
Change the font size when didAnimateFirstHalfOfRotationToInterfaceOrientation: is called.
That way the user won't see the change once the rotation completed. It would be pretty hard to see the font size change then, as the rotation is happening!