I've used the CGContext based routine to fill a rectangle, but this time I actually want to fill all of a rectangle EXCEPT one part of it. I know this is possible in other drawing systems for other platofrm but can it be done with core graphics on iOS?
Both borderWidth and cornerRadius are animatable properties. So you could just animate them directly (using CABasicAnimation). In that rendering, you'd go from no border and no corners to having a border and corners in an animated way.
If you want to animate the rectangular tracing of the border, you'd need to use a CAShapeLayer (because the end of its path is animatable) and provide the illusion that way.
Related
I'm trying to draw a rounded rectangle with transparency with the library Skia.
I get a perfect result if i'm using overlapping without transparency.
But when i'm using transparency, i get this:
That's what i get when i do not overlap:
Even if i modify the radius of the inner rectancle, there're still some overlaps/gabs.
My questitons:
What is the correct way to caluclate the radius of the inner rectangle, when i can accept some missplaced pixels?
Is there another way?
You can use saveLayerAlpha before drawing and then restore after drawing. This allows you to draw multiple paths, shapes, etc with a "global" alpha applied to the layer.
I have a UIImageView displaing an image. This view's layer is masked with CAShapeLayer in order to create circular "hole" in the image. To create the hole I use UIBezierPath with .usesEvenOddFillRule = true.
It works fine when static. But I need that hole to move with user finger. To do that I create new UIBezierPath with even-odd rule each time user moves their finger. On smaller phones with smaller images it looks OK but on iPhone 6 Plus it is choppy.
Any ideas on how to make it smooth are very wellcome. I cannot just move the frame of masking CAShapeLayer - it would move the hole bot also hide some edges of the image. So the only way is to change its .path each time user moves finger and that is slow.
EDIT: matt's answer would work in some scenarios but not in my case: I am not displaying the whole image only a part of it defined by UIBezierPath. This part is most often oval (but can be rectangular or rounded rectangle) and it has "hole" cut in it. While the hole is mowing with users finger the displayed part/shape of the image does not change - it is static.
The ineficient solution that was in place so far wa:
Create UIBezierPath with boundary of displayed part of the image
Set 'even off fill rule' on it
Add UIBezierPath of the hole to it
Set it as path of CAShapeLayer with some opaque fill color
Use that CAShapeLayer as mask of the UIImageView
This procedure was repeated each time a user moved their finger. I cannot simply move the whole mask layer as that would also change the part of the image being displayed. I what it to stay static and move only the hole in it.
it would move the hole bot also hide some edges of the image
Well, I don't agree. Moving the mask is exactly the way to do this. I don't see why you think there's a problem with that. Perhaps the issue is merely that you have not made the mask layer big enough. It does not have to be the same size as the layer it is masking. In this case, it needs to be about 9 times the size of the masked layer (3 horizontal and 3 vertical), so that it will continue to cover the masked the layer no matter how far in any direction the user slides it.
How to make an animation similar to "Slide to unlock" text on a UILabel? (The text gradient is animated left->right) and then the text color adapts to the background.
I think the key to performing this effect is CALayer mask. You can attach a second CALayer to any existing layer as its mask. Then:
The [mask] layer’s alpha channel determines how much of the [parent] layer’s content
and background shows through. Fully or partially opaque pixels allow
the underlying content to show through but fully transparent pixels
block that content.
So the text is going to be the mask and the moving colour is going to be the parent.
The easiest way to deal with the text will be to use a CATextLayer. The easiest way to make the colour gradient will be CAGradientLayer.
To animate the gradient you can use Core Animation, since all properties are animatable. I guess locations is likely to be the best way to achieve the sliding animation.
For convenience you'll probably want to wrap all of that up into a UIView, but you can add layers directly if you prefer.
On my table view, I want to display small circles of certain colors that will provide context for the information. The circles should be in the location that the image would usually be in (the left hand side). Is there an easy way to do this? I was thinking that I could create a new image view and simply draw on it using some drawing routines. The problem is I don't know any of these drawing routines, or at least I don't know how to use them outside of a drawRect function.
Well, the easiest way would be to include the different images in your bundle and conditionally set them to the cell's imageView's image property in cellForRowAtIndexPath:.
However, if you're looking for alternative's you could subclass UITableViewCell, and use CAShapeLayers to draw them programmatically and add them to the cells layer in what ever position you want.
Here's an example of how to use CAShapeLayer to draw a circle:
iPhone Core Animation - Drawing a Circle
I'm drawing a few circles, each filled with an image. When the user pans I'd like to scale/resize the circles. So I called drawRect again and again, redrawing every GCRect until the gesture was completed - of course the animation was very choppy. In my case a UIScrollView doesn't fit the needs, because I don't want to scroll, but to scale the circles while the user is panning.
Is there any way except using OpenGL ES to implement this functionality?
Do you really need custom drawing for this? You can easily clip an image to a circle without drawRect.
Without -drawRect:
Using Core Animation you can set the corner radius of a layer. If all you want is to show an image inside a circle then you can put the image in an image view with a square frame and set the corner radius of the image views layer to half the width of the frame.
Now each time the user drags you can change the bounds and the corner radius of the image views layer. This will make it look like the circle becomes bigger/smaller.
If you require custom drawing
Maybe you are doing some custom shadows or blending that can only be done with Core Graphics. If so, you could apply a scale transform and stretch the image while the user is dragging their finger and only redraw once the finger lifts from the screen. That will be much, much cheaper and is also very easy to implement. Just create a scale transform (CGAffineTransformMakeScale(xScale, yScale);) and set it as the transform on the view with the circle (this will only work if each circle is its own view).
Note: You can still use the same trick (scaling while dragging and then redrawing) if you use the corner radius approach if you require the extra performance.