I'm animating a shrinking object. At any point the user can hit a button to get the current scale factor of the object. (I start by scaling the object up using a CGAffineTransformMakeScale, so the scale factor should be 1 when it reaches its original size). I'm just not sure how to retrieve the current scale factor from the animation UIImageView... Here's my code:
- (void)startShrink {
CGAffineTransform scaleFactor = CGAffineTransformMakeScale(kScaleX, kScaleY);
imageOutline.transform = scaleFactor;
CABasicAnimation *shrink = [CABasicAnimation animationWithKeyPath:#"transform.scale"];
shrink.toValue = [NSNumber numberWithDouble:0.5];
shrink.duration = 2.0;
shrink.fillMode=kCAFillModeForwards;
shrink.removedOnCompletion=NO;
shrink.delegate = self;
[imageOutline.layer addAnimation:shrink forKey:#"shrink"];
}
I tried the following, but I'm not sure m12 is the value I should be retrieving from the transform. Or if in fact this is the right approach:
- (float)calculateScale {
CATransform3D scaleTransform = [(CALayer *)[imageOutline.layer presentationLayer] transform];
float scale = scaleTransform.m12;
NSLog(#"Scale: %g", scale);
return scale;
}
Any advice most appreciated :)
Thanks, Michael.
If you just scale your view uniformly on all axes then scale value should equal to m11 (and m22 as well).
I just ran a sample with your code copy-pasted - it seems that the following 2 lines are redundant:
CGAffineTransform scaleFactor = CGAffineTransformMakeScale(kScaleX, kScaleY);
imageOutline.transform = scaleFactor;
View immediately shrinks by half (I used 0.5 for scale values) and then shrinks twice more with animation
Related
I want to rotate a CGPoint(red rect) around another CGPoint(blue rect) but it changes distance from the origin(blue rect)...when i give 270 in angle it creates the point right above the origin but when i give 90 as angle value it comes down the origin BUT CHANGES THE DISTANCE ALSO almost three times more....I want to keep the distance same and want to rotate CGPoint around another. Please guide any approach for rotation of cgpoints...
distance = 100;
angle = 270*M_PI/180;
rotatedPoint.x = initialPoint.x+distance*cos(angle);
rotatedPoint.y = initialPoint.y+distance*sin(angle);
//rotatedPoint.x = initialPoint.x+tan(angle);
[test setCenter:rotatedPoint];
[test setBackgroundColor:[UIColor redColor]];
Thanks
CGAffineTransform is a handy tool when it comes to rotation, translation, and scaling. To make sure a point is rotated properly, you must translate it to the origin, rotate it, and then translate it back.
To complete your transformation, something like the following should do the trick:
CGPoint pointToRotate = CGPointMake(30, 30);
float angleInRadians = DEGREES_TO_RADIANS(90);
CGPoint distanceFromOrigin = CGPointMake(0 - pointToRotate.x, 0 - pointToRotate.y);
CGAffineTransform translateToOrigin = CGAffineTransformMakeTranslation(distanceFromOrigin.x, distanceFromOrigin.y);
CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(angleInRadians);
CGAffineTransform translateBackFromOrigin = CGAffineTransformInvert(translateToOrigin);
CGAffineTransform totalTransform = CGAffineTransformConcat(translateToOrigin, rotationTransform);
totalTransform = CGAffineTransformConcat(totalTransform, translateBackFromOrigin);
pointToRotate = CGPointApplyAffineTransform(pointToRotate, totalTransform);
And here is the documentation on CGAffineTransform, if you'd like to review it further: http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CGAffineTransform/Reference/reference.html
Please let me know if you need anything else if this doesn't solve your problem!
I'm a beginner and I am doing some exercises to familiarize myself with CALayer ...
I just want to know how to "incline" (or skew) a CALayer 45° angle ?
Thank you.
CALayers have a property, affineTransform that takes a CAAffineTransform. That documentation explicitly notes that:
Scaling, rotation, and translation are
the most commonly used manipulations
supported by affine transforms, but
skewing is also possible.
(emphasis mine, obviously)
There's no built in helper to construct a skew transform, but you could do something like (untested):
CGAffineTransform CGAffineTransformMakeSkew(CGFloat skewAmount)
{
CGAffineTransform skewTransform = CGAffineTransformIdentity;
skewTransform.b = skewAmount;
return skewTransform;
}
Then, for a skew such that things that were verticals stand at 45 degrees to the horizontal you'd use:
layer.affineTransform = CGAffineTransformMakeSkew(1.0f);
CALayers can be transformed using matrix operations. The skew transformation is represented by the following matrix
So if you want to do a skew transformation along the x axis you can use the following sample.
CALayer* layer = [CALayer layer];
layer.frame = CGRectMake(50,50,50,50);
layer.backgroundColor = [UIColor blueColor].CGColor;
[self.window.layer addSublayer:layer];
float theta = -45.0f;
CGAffineTransform t = CGAffineTransformIdentity;
t.b = tan(theta*M_PI/180.0f);
layer.transform = CATransform3DMakeAffineTransform(t);
The following sample will result in a layer that looks like the following
You could do this but you would have to mess with the layer's transform property, which is a struct CATransform3D. You're going to have to do some vector math to do this, as you . See the compute_transform_matrix(...) function from this answer for more details.
You'll want to do something like this:
CGRect r = layer.bounds;
layer.transform = compute_transform_matrix(r.origin.x, r.origin.y, r.size.width, r.size.height,
r.size.height, r.origin.y, r.size.width + r.size.height, r.origin.y,
r.origin.x, r.origin.y + r.size.height, r.size.width, r.origin.y );
Check my math on this. It should be right.
There are a lot of resources on how transforms work and it takes a bit of time to really understand them (at least for me!), here is some straight-to-the-point code that makes sure to indicate to which axis the transform is applied.
/*!
* Positive `skewX` creates a shift to the left.
* Negative `skewX` creates a shift to the right.
*
* `skewX` is NOT pixel based. Test values of 0.0f - 1.0f.
*/
CGAffineTransform CGAffineTransformMakeSkewX(CGFloat skewX)
{
return CGAffineTransformMakeSkew(skewX, 0.0f);
}
/*!
* Positive `skewY` creates a shift to the bottom.
* Negative `skewY` creates a shift to the top.
*
* `skewY` is NOT pixel based. Test values of 0.0f - 1.0f.
*/
CGAffineTransform CGAffineTransformMakeSkewY(CGFloat skewY)
{
return CGAffineTransformMakeSkew(0.0f, skewY);
}
/*!
* Positive `skewX` creates a shift to the left.
* Negative `skewX` creates a shift to the right.
*
* Positive `skewY` creates a shift to the bottom.
* Negative `skewY` creates a shift to the top.
*
* The skew values are NOT pixel based. Test values of 0.0f - 1.0f.
*/
CGAffineTransform CGAffineTransformMakeSkew(CGFloat skewX, CGFloat skewY)
{
return CGAffineTransformMake(1.0f, skewY, skewX, 1.0f, 0.0f, 0.0f);
}
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.
I'd like the shadow applied correctly after rotation. This is my code:
myButton.transform = CGAffineTransformMakeRotation(M_PI / 180.0 * 90.0);
myButton.layer.shadowOffset = CGSizeMake(12.0, 12.0);
myButton.layer.shadowRadius = 2.0;
myButton.layer.shadowOpacity = 0.8;
myButton.layer.shadowColor = [UIColor blackColor].CGColor;
Without rotation the shadow looks fine:
But after rorating it by 90° the shadow is rotated as well:
Is there anything I can do about it without overriding the drawRect method and do low level drawing? Or maybe some method which corrects the shadowOffset with a given rotation angle? It's easy to correct the offset by hand for 90° so this is no option ;)
It should look like this:
Thanks in advance!
With help of Bartosz Ciechanowski this works now!
float angleInRadians = M_PI / 180.0 * -35.0;
myButton.transform = CGAffineTransformMakeRotation(angleInRadians);
myButton.layer.shadowOffset = [self correctedShadowOffsetForRotatedViewWithAngle:(angleInRadians)
andInitialShadowOffset:CGSizeMake(12.0, 12.0)];
myButton.layer.shadowRadius = 2.0;
myButton.layer.shadowOpacity = 0.8;
myButton.layer.shadowColor = [UIColor blackColor].CGColor;
This results in:
instead of
Assuming anAngle is in radians:
- (CGSize)correctedShadowOffsetForRotatedViewWithAngle:(CGFloat)anAngle
andInitialShadowOffset:(CGSize)anOffset
{
CGFloat x = anOffset.height*sinf(anAngle) + anOffset.width*cosf(anAngle);
CGFloat y = anOffset.height*cosf(anAngle) - anOffset.width*sinf(anAngle);
return CGSizeMake(x, y);
}
I think you could try using
myButton.layer.shadowOffset = CGSizeMake(-12.0, -12.0);
to
myButton.layer.shadowOffset = CGSizeMake(12.0, 12.0);
Just try using this, if it works.Either you need to set the shadow with Trial & Error method.
This is just a suggestion or a trick if could solve your problem.
I have a UIView subclass that I'm drawing a PDF onto (using a CATiledLayer). I also need to draw on a specific region of that PDF, however the coordinate plane of the CATiledLayer when using CG to draw is way screwy.
See image:
I have a point (200,200), that I need to convert to the CATiledLayer's coordinate system, which is the 2nd plane shown above. I've tried doing this with some transforms, but nothing seems to work.
Thanks!
Here is what I had to do (using the example points/plane above):
//rotatation origin
CGPoint rotateOrigin = CGPointMake(0,0);
//rotatation transform
CGAffineTransform translateTransform = CGAffineTransformMakeTranslation(rotateOrigin.x, rotateOrigin.y);
//rotate the plane 90 degrees
float radians = 90 * (M_PI / 180);
CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(radians); CGAffineTransform customRotation = CGAffineTransformConcat(CGAffineTransformConcat( CGAffineTransformInvert(translateTransform), rotationTransform), translateTransform);
CGAffineTransform m1 = CGAffineTransformIdentity;
CGPoint startPoint = CGPointApplyAffineTransform(CGPointMake(200,200),m1);
//rotated point
CGPoint rotatedPoint = CGPointApplyAffineTransform(startPoint, customRotation);
//final rotated point- after adjusting for the rotation
rotatedPoint = CGPointApplyAffineTransform(rotatedPoint, CGAffineTransformMakeTranslation(500,-500));