I would like to render a CALayer to a UIImage including the shadow if any is present on the CALayer.
This all works fine except that I cannot determine (other than empirically) what the relation between shadowRadius and point/pixel might be.
That is, I create a parent CALayer with a transparent background and an inflated size that would include the target CALayer's shadow. Then I render the parent CALayer.
Empirically, it seems I can tightly include the entire shadow for any shadowRadius by setting the parent layer's size to the {width, height} of the target layer's size + 3.75 * shadowRadius.{width,height}.
It's kind of weird and hackish and I'd like to know the real answer/derivation.
It seems the blur is a guassian blur so this is going to be involved in the answer somehow I suppose...
Using 2 * shadowRadius clearly clips:
Using 5 * shadowRadius is clearly too large:
And 3.75 * shadowRadius seems to be spot on (but WHY?!):
Related
My app draws layer-backed labels over a NSImageView.
The image view displays an image, and a tint color over that image.
This ensures that the contrast between the labels and the background image works.
As you can see, subpixel antialiasing is enabled and works correctly.
When you hover over those labels, they animate the frame property (Actually the view containing them).
While animating, the subpixel antialiasing is disabled, and when done enabled again.
This looks incredibly weird.
The layer is never redrawn, and the subpixel antialiasing doesn't have to change.
So I don't see a good reason why it shouldn't be displayed when animating.
I've tried everything I can think of.
Making the NSTextField opaque
Making the CATextLayer opaque
Giving the NSTextField a background-color
Giving the CATextLayer a background-color
Always the same result.
Disabling subpixel antialiasing for the labels is not an option, since it's not well readable on non-retina devices.
EDIT
I forgot that the layer is replaced with a presentationLayer while animating.
This layer probably does not support subpixel antialiasing, which is why it's disabled.
Now the question is if I can replace this presentationLayer with a CATextLayer.
What I also noticed is that setting shouldRasterize to YES enabled subpixel antialiasing also for animation, but only against the background color. So no background-color will bring no subpixel antialiasing.
Is there any way that you can post a piece of sample code? I quickly mocked up an NSWindow, added an NSImageView, added a background-less NSTextField with setWantsLayer: set to YES. In my applicationDidFinishLaunching: I set a new rect on the NSTextField's Animator frame, but I didn't see any pixelation.
The problem is with positioning of the text layer. Let's presume you use left alignment. The text will look good if x and y coordinates of the layer's frame origin are rounded numbers. For example:
CGFloat x = 10.6;
CGFloat y = 10.3;
textLayer.frame = CGRectMake(x, y, width, height); // the text will be blur.
textLayer.frame = CGRectMake(round(x), round(y), width, height); // the text will not be blur.
So, the first problem may be that the coordinates you assign to the layer's frame are not rounded.
The tricky part is that the edge of the layer may still be not aligned with pixels even if you think you passed rounded coordinates. This may happen if the anchorPoint of your layer is (0.5, 0.5), which is the default value. If you set:
textLayer.position = CGPointMake(10.0, 10.0);
you may think it should draw the text sharp. However, position point is in the center of the layer here, and depending on the layer's width and height the left and top edge's coordinates may be fractional numbers.
If you want to make a quick test do this.
Use textLayer.frame = frame instead of using position and anchor point, it will assign the coordinates directly to the frame.
Make sure the numbers you use in the frame are rounded.
Do not mess with rendering mechanism, remove the code that changes shouldRasterize, antialiasing, etc.
If this makes the text sharp, you can start using the anchor point and position and to see how the result changes.
I can't find an answer for this one.
I would like to know how to have the image size in a calayer's to be lower than calayer's bound's size.
I've got several pawns in an iPad game, each is a CALayer and I have them resize simply with a contentsGravity=kCAGravityResizeAspect. Image is 128x128 inside of a CALayer of 30x30 so the image gets resized automatically to 30x30 and because of both being a box, aspect ratio maintains and works.
Here I set CALayer's bounds proportional relative to superview's size, so the Pawns always present the same relative size to the view. This one is inside my sprite class subclass of calayer:
-(void) setSpriteScaleToDice {
CGFloat newSize = [self superlayer].bounds.size.width * 0.066666667f;
self.bounds=CGRectMake(0.0f, 0.0f, newSize, newSize);
self.contentsGravity = kCAGravityResizeAspect;
}
Note that in my case the CALayer bounds gets a maximum of 30x30 which is small for a touch. That's the problem I'm facing, due to this small size it's difficult to "touch" them, sometimes touch fails...
One of the ideas that I'm thinking is to increase the "bounds" of the calayer, while keeping the image at its original size. The problem is that I've search a lot and tried several options with contentsGravity, contentsCenter, contentsScale, etc... without success.
In particular, as per apple docs looks like the way to go is with contentsCenter (and not using contentsGravity), however I get deformation in the bitmap...
Please, any idea is really welcome, and thanks in advance,
Luis
This is probably a silly question, but why are you using CALayers for this instead of UIViews? UIImageView has a contentMode property that lets you do this easily (not to mention being easier to use for touch event handling).
That said, CALayer has a contentsRect property that appears to let you define a sub-rectangle for contents to be drawn within, so that may let you do what you want.
Another option would be to place your image layer inside a larger layer and use that for the hit test.
CAlayer CGFloat contentsScale
/* Defines the scale factor applied to the contents of the layer. If
* the physical size of the contents is '(w, h)' then the logical size
* (i.e. for contentsGravity calculations) is defined as '(w /
* contentsScale, h / contentsScale)'. Applies to both images provided
* explicitly and content provided via -drawInContext: (i.e. if
* contentsScale is two -drawInContext: will draw into a buffer twice
* as large as the layer bounds). Defaults to one. Animatable. */
If you want your image drawn in the CALayer at a size other than the CALayer you need to create your own drawInContext: method and draw the image rather than setting the CALayer's contents property. Do not set the contents property, create your own to track the image you want to draw.
I have a problem understanding how the parameter passed to the drawInRect method is defined when a rotation transformation is performed on a UIView.
To give an example I have a UIView which I rotated with an angle of 307 degree.
In the drawInRect method I log the following:
self.frame: {{103.932, 273.254}, {64.3007, 84.3374}}
rect (the variable passed as parameter:{{0, 0.102913}, {18, 89}}
The problem is that according to the documentation I should not draw outside of rect, but considering what I should draw, there is no way my images will fit there.
Can anyone explain to me how I am supposed to use drawInRect in the case my UIView is rotated ?
To give more detail about my problem, here is what I do:
I have a scrollview with a contentView inside (subclassed). I add my UIViews in the content view.
The views in question are composed of a handler image (bottom left) and the main image (top right). Users are supposed to grab the view by pressing the handler but that's not the point.
The drawInRect method of the UIView contains the following:
[_image drawInRect:CGRectMake(handlerSize.width, 0, _image.size.width, _image.size.height)];
CGSize size = CGSizeMake(kHandPickerWidth/self.scrollViewScale, kHandPickerHeight/self.scrollViewScale);
[_handPickerImage drawInRect:(0, _image.size.height, size.width, size.height)];
The UIViews objects are added at viewWillAppear in the content view doing the following:
first instanciate,
then addSubview:
then I set the scrollViewScale parameter,
then I set the frame parameter (according to the top right image displayed (which may vary)
then I rotate the UIView.
Starting from line three, the code is executed from the
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
to make sure every variable is set properly when displayed is needed.
The line defining the size variable is to adjust the marker's size no mater the zoomScale value of the scroll view.
You basically just draw as you would normally, and the painting will be rotated by iOS for you. You can get this transformation information if you would want to.
You need to get a reference to the currect graphics context:
CGContextRef ctx = UIGraphicsGetCurrentContext();
Then query the transformation matrix directly:
CGAffineTransform tf = CGContextGetCTM(ctx);
NSLog(#"current ctm: %#",NSStringFromCGAffineTransform(tf));
or better, get the transfrom from your drawing function to the device:
CGAffineTransform tf = CGContextGetUserSpaceToDeviceSpaceTransform(ctx);
NSLog(#"user->device transform: %#",NSStringFromCGAffineTransform(tf));
And in drawRect: you should not rely too much on the passed CGRect, because it serves mostly as a hint to what piece of the view needs updating. (e.g. because you called -setNeedsDisplayInRect: on it). To get the actual bounds where your view lives in, use self.bounds.
Drawing outside of the CGRect is no real problem, but will only hurt performance a little.
edit
ps. to clarify: self.frame is the frame of your view in the parent view coordinate system. It changes if you move, rotate or otherwise transform the view. self.bounds is the frame of your view in its own coordinate system, and (therefore) remains constant under changes of position or transformations.
So I found a solution to my problem:
I was setting the frame parameter multiple times with some CGAffineTransformation defined which is not supposed to be done.
Now each time I need to reset the frame I reset the affine transform, change the frame and set the back the affine transform.
Everything works as supposed to this way.
Cocoa's NSScrollView is horribly under-explained. I hope someone here knows what it's all about and can spare me a few seconds.
So I have a custom NSView. I implement -drawRect: for it to draw something, fill itself with colour, whatever. Then I have an NSScrollView wrapping it (set up through the interface Builder).
Now the inner, custom, view must have a size larger than that which fits in the outer scroll view—for it to scroll. That much I realise. I have incidentally configured it so that the scroll view adjusts to the surrounding window’s size, but that shouldn’t matter.
I override my inner view’s -frame method to return a frame sized at least 1000x1000.
- (NSRect)frame {
CGFloat w = 1000;
CGFloat h = 1000;
if (self.superview.bounds.size.width > w)
w = self.superview.bounds.size.width;
if (self.superview.bounds.size.height > h)
h = self.superview.bounds.size.height;
return NSMakeRect(0, 0, w, h);
}
Here’s the outcome, which I have trouble interpreting:
I can scroll when the scroll view encloses an area smaller than 1000x1000
BUT
The only area filled with colour (i.e. that my -drawRect: method has any effect on) is
as large as the scroll view’s bounds
located at (0,0. I use flipped, so that’s top left, and it ends up being outside the visible area after scrolling.
The visible area that lies outside this irrelevant rectangle is not painted at all.
I don’t know anything beyond this point. It seems like the rect for drawing is clipped to the scroll view’s position in the window, and size, or something—but it does not take the scrolled "location" into account.
It should be noted that I don't really expect anything else to happen. I feel I am missing a piece, but can't find which. Sorry for the wall of text, but I can’t explain better right now. I hope it is easier to answer than it is to ask.
Regards and hope,
Not Rick Astley
It's a very very very bad idea to overwrite -frame. There is so much that depends on the actual instance variable having a correct value. Instead try to set the frame to the one you want using setFrame:, that might fix all your problems if you're lucky...
I agree with Max's warning that you shouldn't override -frame. If you want to constrain the set frame, override its setter ( -setFrame: ) and the designated initializer ( -initWithFrame: ) and adjust the proposed frame as desired.
Regarding your overall problem, I wonder if your problem is conceptual. The argument for -drawRect: (the dirty rectangle you're asked to redraw) is useful if you're drawing something that you can redraw incrementally in parts (like a grid - any grid blocks intersecting dirtyRect can be redrawn and the rest can be ignored). If you're doing something that has to be completely redrawn, you should use [self bounds] and not the dirty rect passed at drawRect.
For example, if you have just a standard gradient background, it's difficult to tell from dirtyRect which part of the gradient to redraw and infinitely easier just to redraw the whole view with the gradient, ignoring dirtyRect altogether.
You're right in assuming that only the area of your view exposed by the scroll view's clip rect will normally be asked to redraw when scrolling. There're also interactions with the scroll view's -copiesOnScroll to consider.
I hope this helps.
Use of the NSScroller really relies on a solid understanding of the MVC paradigm. Apple's docs really focus on showing a photo and a set of text, but not much else. The use of NSScrollView is something that I've struggled with in the past.
First off, do not override frame. Use setFrame to tell the scrollView how large the working area is, and then just simply draw in the area the frame encompasses. As I understand it, a custom NSView and the encompassing NSScrollView takes care of the rest, such as what to draw where when. In other words, ignore the bounds of the rect passed into drawRect and instead draw within the bounds of the frame you sent to scrollView; don't worry about what is visible and what isn't because that is the job of the framework.
Here is where the MVC paradigm comes in: setFrame should be used when your Model is updated. So, if an object falls outside of the current bounds of the frame, then use setFrame to set the newly expanded bounds, and then draw within that area.
I have a somewhat transparent view (alpha = 0.6) that has some subviews. I'd like one of the subviews (a UILabel) to be drawn with alpha of 1.0 because the blending makes the text difficult to read but by adding it as a subview of the main view it has adopted its parent's alpha value. Is there a way to override this behavior? I believe I'll have to remove it from the subview but wanted to ask and see if maybe I'm missing something.
Brian is right.
For example :
view.backgroundColor = [UIColor colorWithWhite:0 alpha:0.6];
will make a Black background in alpha 0.6 and other views won't be affected.
Another approach which worked easily is to not modify the alpha channel on the UIView. Instead, modify the alpha layer on the backgroundColor object of the UIView.
Of course this depends on why you made the alpha layer transparent, but it worked well for my requirements.
You are correct. You'll have to move the UILabel out of the transparent view to get it to render as non-transparent.