I have a UIBezierPath and I would like to get its mirror image. How can I accomplish this?
// Method for generating a path
UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];
// ? now I would like to mirror myPath ?
// Method for generating a path
UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];
// Create two transforms, one to mirror across the x axis, and one to
// to translate the resulting path back into the desired boundingRect
CGAffineTransform mirrorOverXOrigin = CGAffineTransformMakeScale(-1.0f, 1.0f);
CGAffineTransform translate = CGAffineTransformMakeTranslation(boundingRect.width, 0);
// Apply these transforms to the path
[myPath applyTransform:mirrorOverXOrigin];
[myPath applyTransform:translate];
It should be noted that you might need additional code depending on where in the overall view the path you are trying to mirror is.
If you are trying to mirror a path that takes up the whole view (or is at least flush with the 0 coordinate of the axis you are mirroring over), then #wbarksdale's answer will work for you. However, if you are trying to mirror a path thats a small section of the overall view thats somewhere in the middle of the view, then you need to do more work. In general, the algorithm is like this
//this rect should be the bounds of your path within its superviews
//coordinate system
let rect = myPath.bounds
//first, you need to move the view all the way to the left
//because otherwise, if you mirror it in its current position,
//the view will be thrown way off screen to the left
path.apply(CGAffineTransform(translationX: -rect.origin.x, y: 0))
//then you mirror it
path.apply(CGAffineTransform(scaleX: -1, y: 1))
//then, after its mirrored, move it back to its original position
path.apply(CGAffineTransform(translationX: rect.origin.x + rect.width, y: 0))
In general, the algorithm should be
Move the path either to the very left or the very top of the view
depending on whether you are flipping horizontally or vertically, using CGAffineTransform(translateX....)
Mirror the view using CGAffineTransform(scaleX....
Move the view back to its original position using CGAffineTransform(translateX....)
I case your path in not centered to (0,0) this code is correct:
// Method for generating a path
UIBezierPath *myPath = [self generateAPathInBounds:boundingRect];
// Create two transforms, one to mirror across the x axis, and one to
// to translate the resulting path back into the desired boundingRect
CGAffineTransform mirrorOverXOrigin = CGAffineTransformMakeScale(-1.0f, 1.0f);
CGAffineTransform translate = CGAffineTransformMakeTranslation(CGRectGetMidX(boundingRect), 0);
CGAffineTransform translateBack = CGAffineTransformMakeTranslation(-CGRectGetMidX(boundingRect), 0);
// Apply these transforms to the path
[myPath applyTransform:translate];
[myPath applyTransform:mirrorOverXOrigin];
[myPath applyTransform:translateBack];
Related
I'm trying to setup the collison bounding path of a custom UIView. What I currently do is converting a SVG file to a path using PocketSVG and creating an UIBezierPath from it. Here's my code:
#implementation CustomView {
UIBezierPath * _mask;
CGPathRef _myPath;
}
- (UIDynamicItemCollisionBoundsType) collisionBoundsType {
return UIDynamicItemCollisionBoundsTypePath;
}
- (UIBezierPath *) collisionBoundingPath {
_myPath = [PocketSVG pathFromSVGFileNamed:#"line5"];
_mask = [UIBezierPath bezierPathWithCGPath:_myPath];
return _mask;
}
It works "correctly" but the UIBezierPath is drawn at the center of my view so this is what I get:
Left: Actual behavior ---> Right: Expected behavior
And since the collision bounds are invisible the collision seems to happen before touching the view visually (they are actually touching because of the origin of the collision bounds path).
According to Apple documentation regarding collisionBoundingPath:
The path object you create must represent a convex polygon with
counter-clockwise or clockwise winding, and the path must not
intersect itself. The (0, 0) point of the path must be located at the
center point of the corresponding dynamic item. If the center point
does not match the path’s origin, collision behaviors may not work as
expected.
So my main question is, since the (0,0) coordinates of the path must be at the center of my view, how can I achieve what I'm looking for? The perfect scenario would be if UIBezierPath start drawing at the origin of its UIView but since I'm adding a path from a SVG it is automatically draw from the center of the view.
You can use a transformation to move the CGPath into the appropriate position. For example:
- (UIBezierPath *) collisionBoundingPath {
_myPath = [PocketSVG pathFromSVGFileNamed:#"line5"];
CGAffineTransform translation = CGAffineTransformMakeTranslation(-self.bounds.size.width * 0.5,-self.bounds.size.height * 0.5);
CGPathRef movedPath = CGPathCreateCopyByTransformingPath(_myPath,&translation);
_mask = [UIBezierPath bezierPathWithCGPath:movedPath];
return _mask;
}
I been working on an iOS app which should display indoor blueprints. You should be able to switch between floors and each floor image is controlled by gesture recognisers to handle pan, rotate and scale.
I have been using this example for the gesture recognisers: https://github.com/GreenvilleCocoa/UIGestures/blob/master/UIGestures/RPSimultaneousViewController.m
So now to the problem. Whenever the user switch floor I want to keep the transformation of the image as well as the corresponding center lat/lng. However, the new image can have another rotation offset and aspect ratio.
I have been able to update the new frame of the image with the new size and update the transform with the new rotation offset and verified it. It is when I try to calculate the new center point I can not get it to work. The following code is how I currently do it and it works as long as the view is not rotated:
-(void)changeFromFloor:(int)oldFloorNr toFloor:(int)newFloorNr
{
CGPoint centerPoint = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
// This is the old non transformed center point.
CGPoint oldCenterOnImage = [self.layer convertPoint:centerPoint toLayer:self.mapOverlayView.layer]; // Actual non transformed point
// This point is verified to be the corresponding non transformed center point
CGPoint newCenterOnImage = [self calculateNewCenterFor:oldCenterOnImage fromFloor:oldFloorNr toFloor:newFloorNr];
// Change image, sets a new image and change the fram of mapOverlayView
[self changeImageFromFloor:oldFloorNr toFloor:newFloorNr]
// Adjust transformed rotation on map if new map have different rotation
[self adjustRotationFromFloorNr:oldFloorNr toFloorNr:newFloorNr];
CGPoint centerOfMapOverlay = CGPointMake((self.mapOverlayView.frame.size.width / 2), (self.mapOverlayView.frame.size.height / 2));
CGPoint newCenterOnImageTransformed = CGPointApplyAffineTransform(newCenterOnImage, self.mapOverlayView.transform);
CGFloat newCenterX = centerPoint.x + centerOfMapOverlay.x - newCenterOnImageTransformed.x;
CGFloat newCenterY = centerPoint.y + centerOfMapOverlay.y - newCenterOnImageTransformed.y;
// This only works without any rotation
self.mapOverlayView.center = CGPointMake(newCenterX, newCenterY);
}
Any idea where I go wrong? I have been working with this problem some days now and I can not seem to figure it out.
Please let me know if I need to add something or if something is unclear.
Thanks!
Code added after help was given:
CGPoint centerOfMapOverlay = CGPointMake(
(self.mapOverlayView.bounds.size.width / 2,
(self.mapOverlayView.bounds.size.height / 2)
);
centerOfMapOverlay = CGPointApplyAffineTransform(
centerOfMapOverlay,
self.mapOverlayView.transform
);
If you change the transform on it's view then the frame property becomes undefined. You should instead use the center property to change the view's position and bounds.size to change the view's size.
I've got a main CALayer which contains a few sublayers. I rotated the main layer by 89 degrees around the x-Axis, so I'm barely seeing it (it's close to being a slice in the middle of the screen now).
CATransform3D moveToOrigin = CATransform3DMakeTranslation(-self.bounds.size.width / 2.0f, -self.bounds.size.height / 2.0f, 0.0);
CATransform3D rotateX = CATransform3DConcat(moveToOrigin, CATransform3DMakeRotation(DEGREES_TO_RADIANS(89.0), 1.0, 0.0, 0.0));
CATransform3D finalTransform = CATransform3DConcat(rotateX, CATransform3DMakeTranslation(self.bounds.size.width / 2.0f, self.bounds.size.height / 2.0f, 0.0));
mainLayer.transform = finalTransform;
Now I want to move each sublayer along the z-Axis, so that it looks like a stack with spacing between the layers. Unfortunately, all I see is all sublayers flat on the main layer.
for (int i = 0; i < self.sublayers.count; i++) {
CALayer *aLayer = _layers[i];
transform = CATransform3DMakeTranslation(0.0, 0.0, 100 * i);
}
The weird thing is that moving along the x or y Axis works like a charm.
Does it have something to do with that sublayer transform?
Is changing the zPosition property the same as moving the layer with CATransform3D along the z-axis?
When layers are rendered they are generally being flattened so even though they may contain sublayers with different Z values, the rendered layer is going to be flat. However, there is one layer class which doesn't have this behavior and it is called CATransformLayer. It doesn't do have any contents of its own but it also leaves the sublayers intact.
guys!
I need to draw some image to CGContext.This is the relevant code:
CGContextSaveGState(UIGraphicsGetCurrentContext());
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGRect rect = r;
CGContextRotateCTM(ctx, DEGREES_TO_RADIANS(350));
[image drawInRect:r];
CGContextRestoreGState(UIGraphicsGetCurrentContext());
Actually,the rectangle is rotate and display on a area what is not my purpose.I just want to
rotate the image and display on the same position.
Any ideas ?????
Rotation is about the context's origin, which is the same point that rectangles are relative to. If you imagine a sheet of graph paper in the background, you can see what's going on more clearly:
The line is the “bottom” (y=0) of your window/view/layer/context. Of course, you can draw below the bottom if you want, and if your context is transformed the right way, you might even be able to see it.
Anyway, I'm assuming that what you want to do is rotate the rectangle in place, relative to an unrotated world, not rotate the world and everything in it.
The only way to rotate anything is to rotate the world, so that's how you need to do it:
Save the graphics state.
Translate the origin to the point where you want to draw the rectangle. (You probably want to translate to its center point, not the rectangle's origin.)
Rotate the context.
Draw the rectangle centered on the origin. In other words, your rectangle's origin point should be negative half its width and negative half its height (i.e., (CGPoint){ width / -2.0, height / -2.0 })—don't use the origin it had before, because you already used that in the translate step.
Restore the gstate so that future drawing isn't rotated.
What worked for me was to first use a rotation matrix to calculate the amount of translation required to keep your image centered. Below I assume you've already calculated centerX and centerY to be the center of your drawing frame and 'theta' is your desired rotation angle in radians.
let newX = centerX*cos(theta) - centerY*sin(theta)
let newY = centerX*sin(theta) + centerY*cos(theta)
CGContextTranslateCTM(context,newX,newY)
CGContextRotateCTM(context,theta)
<redraw your image here>
Worked just fine for me. Hope it helps.
use following code to rotate your image
// convert degrees to Radians
CGFloat DegreesToRadians(CGFloat degrees)
{
return degrees * M_PI / 180;
};
write it in drawRect method
// create new context
CGContextRef context = UIGraphicsGetCurrentContext();
// define rotation angle
CGContextRotateCTM(context, DegreesToRadians(45));
// get your UIImage
UIImage *img = [UIImage imageNamed:#"yourImageName"];
// Draw your image at rect
CGContextDrawImage(context, CGRectMake(100, 0, 100, 100), [img CGImage]);
// draw context
UIGraphicsGetImageFromCurrentImageContext();
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Rotate CGPath without changing its position
I searched and tested a variety of code for a couple of hours and I can't get this to work.
I am adding an arbitrary UIBezierPath at a random location to a CAShapeLayer which gets added to a view. I need to rotate the path so that I can handle device rotations. I can rotate the layer instead of the path. I just need the result to be rotated.
I already have methods to handle transforming the bezier path by scaling and translation. It works great, but now I need to simply rotate 90 degrees left or right.
Any recommendations on how to do this?
Basic code:
UIBezierPath *path = <create arbitrary path>
CAShapeLayer *layer = [CAShapeLayer layer];
[self addPathToLayer:layer
fromPath:path];
// I could get the center of the box but where is the box center for the view it is in?
// CGRect box = CGPathGetPathBoundingBox(path.CGPath);
// layer.anchorPoint = ? How to find the center of the box for the anchor point?
// Rotating here appears to rotate around 0,0 of the view
layer.transform = CATransform3DMakeRotation(DegreesToRadians(-90), 0.0, 0.0, 1.0);
I see the following post:
BezierPath Rotation in a UIView
I suppose I could rotate as-is and then translate the path back into place. I just need to figure out what the translation values would be.
I should also state that what I am seeing after I try to rotate is that the image moves off-screen somewhere. I tried rotating 25 degrees to see movement and it pivots around the view's origin of 0,0 so that if I rotate 90 degrees the image is off-screen. I am running these test WITHOUT rotating the device - just to see how rotation works.
UPDATE #1 - 12/4/2012: For some bizarre reason if I set the position to a value I found empirically it moves the rotated bezier path into the correct position after rotation:
layer.position = CGPointMake(280, 60);
This values are a guess from starting/stopping the app and making adjustments. I have no idea why I need to adjust the position on rotation. The anchor point should be in the center of the layer. However, I did find that both the frame and position of a CAShapeLayer are all ZERO even though the path is set, and also the fact that the path is in the correct position within the view. The 280, 60 position shifts the path into what would be the center of the path bounding box when a rotation of +90 is made. If I change the rotation value I need to adjust the position. I should not have to do this manually adjustment.
I think a last resort is to somehow convert the bezier path to an image and then add it. I found that if I set the layer content to an image, then rotate, it rotates about its center point with no positional adjustment needed. Not so with setting the path.
UPDATE #2 12/4/2012 - I tried setting the frame and with fiddling I get it to center as follows:
CGRect box = CGPathGetPathBoundingBox(path.CGPath);
CGRect rect = CGRectMake(0, 0, box.origin.x + (3.5 * box.size.width), box.origin.y + (3.5 * box.size.height));
layer.frame = rect;
layer.transform = CATransform3DMakeRotation(DegreesToRadians(90), 0.0, 0.0, 1.0);
Why multiply by 3.5? I have no clue. I found that adding the box origin with about 3.5 times the size of the box shifts the rotated CAShapeLayer path to about where it should be.
There must be a better way to do this. This is a better solution than my previous post since the frame size does not depend on the rotation angle. I just don't know why the frame needs to be set to the value I am setting it to. I THOUGHT it should be
CGRectMake(0, 0, box.origin.x + (box.size.width / 2), box.origin.y + (box.size.height / 2));
However, it shifts the image to the left too much.
Another clue I found is that if I set the frame of [self view].frame (the frame of the entire parent view, which is the screen of the iPhone), then rotate, the rotation point is the center of the screen, an the path/image orbits around this center point. This is why I tried shifting the frame to what the center of the path should be so that it orbits around the box center.
UPDATE #3 12/4/2012 - I tried to render the layer as an image. However, it appears that just setting the path of a layer does not make it an "image" in the layer since it is empty
CGRect box = CGPathGetPathBoundingBox(path.CGPath);
layer.frame = box;
UIImage *image = [ImageHelper imageFromLayer:layer]; // ImageHelper library I created
CAShapeLayer *newLayer = [CAShapeLayer layer];
newLayer.frame = CGRectMake(box.origin.x, box.origin.y, image.size.width, image.size.height);
newLayer.contents = (id) image.CGImage;
It appears that rotating the layer with its path set is no different than simply rotating the bezier path itself. I will go back to rotating the bezier path and see if I can fiddle with the position elements or something. There's got to be a solution to this.
Goal: Rotate a UIBezierPath around its center point within the view it was originally created in.
UPDATE #4 12/4/2012 - I ran a series of tests measuring the values needed for translation in order to place a UIBezierPath in its previous center location.
CGAffineTransform rotate = CGAffineTransformMakeRotation(DegreesToRadians(-15));
[path applyTransform:rotate];
// CGAffineTransform translate = CGAffineTransformMakeTranslation(-110, 70); // -45
CGAffineTransform translate = CGAffineTransformMakeTranslation(-52, -58); // -15
[path applyTransform:translate];
However, the ratios of x/y translations do not correspond so I cannot extrapolate what translation is required based on the angle. It appears that 'CGAffineTransformMakeRotation' uses some arbitrary anchor put to make the rotation, which at the moment appears to be maybe (viewWidth / 2, 0). I am making this much harder than it needs to be. There's something I am missing to make a simple rotation so that the center point is maintained. I just need to "spin" the path 90 degrees left or right.
UPDATE #5 12/4/2012 - After running additional tests it appears that the anchor point for rotating a UIBezierPath is the origin from where all of the points were drawn. In this case the origin is 0,0 and all of the points are relative to that point. Therefore, it a rotation is applied, the rotation is occurring around the origin, and is why the path shifts up-right on -90 and up-left on 90. I need to somehow set the anchor point for the rotation to the center so it "spins" around the center, rather than the original origin point. 12 hours spent on this one issue.
After some detailed analysis and graphing the bounding box on paper I found my assertion that the origin of 0,0 is correct.
A solution to this problem is to translate the path (the underlying matrix) to the origin, with the center of the bounding box at origin, rotate, then translate the path back to its original location.
Here's how to rotate a UIBezierPath 90 degrees:
CGAffineTransform translate = CGAffineTransformMakeTranslation(-1 * (box.origin.x + (box.size.width / 2)), -1 * (box.origin.y + (box.size.height / 2)));
[path applyTransform:translate];
CGAffineTransform rotate = CGAffineTransformMakeRotation(DegreesToRadians(90));
[path applyTransform:rotate];
translate = CGAffineTransformMakeTranslation((box.origin.x + (box.size.width / 2)), (box.origin.y + (box.size.height / 2)));
[path applyTransform:translate];
Plug in -90 degrees to rotate in the other direction.
This formula can be used when rotating the device from portrait to landscape and vice/versa.
I still don't think this is the ideal solution but the result is what I need for now.
If anyone has a better solution for this please post.
UPDATE 12/7/2012 - I found what I think is the best solution, and very simple as I though it would be. Rather than using rotate, translate, and scale methods on the bezier path, I instead extract the array of points as CGPoint objects, and scale/translate them as needed based on the view size as well as the orientation. I then create a new bezier path and set the layer to this path.
The result is perfect scaling, translation, rotation.