Add Catextlayer on Top of Nsimageview

Add CATextLayer on Top of NSImageView

You needs explicitly say NSImageView wantsLayer before use layers, like below

self.img_view.wantsLayer = true

let myTextLayer = CATextLayer()
myTextLayer.string = "My text"
myTextLayer.foregroundColor = NSColor.cyan.cgColor
myTextLayer.frame = self.img_view.bounds

self.img_view.layer.addSublayer(myTextLayer)

NSImageView with CALayer on Top

Thanks to mohacs, he/she answered the question in this comment ―

you can try changing z order of the layer. http://stackoverflow.com/questions/25371109/z-index-of-image-and-separator-in-uitableviewcell/25372394#25372394 – mohacs Aug 30 '14 at 21:04

Displaying several layered images into an NSView

I figured it out: the problem is that I needed to specify a frame for my sublayers

@IBOutlet weak var mapImageView: NSImageView!
@IBOutlet weak var countriesView: NSView!

override func viewDidLoad() {
    super.viewDidLoad()

    mapImageView.image = NSImage(named: "world")?.tint(color: .white)

    countriesView.wantsLayer = true

    let usLayer = CALayer()
    usLayer.contentsGravity = .resizeAspect
    usLayer.contents = NSImage(named: "US")
    usLayer.frame = countriesView!.layer!.frame
    countriesView?.layer?.addSublayer(usLayer)
}

Annotating over an NSImageView with CALayers, layer-hosting or layer-backed?

The solution I went for was to not alter the NSImageView subclass's layer at all. Instead I added a subview to the NSImageView subclass, constrained the view such that is has the same bounds as the parent, and then made this subview layer-hosting. It is then possible to add sublayer to this 'annotation' view's layer. In this way I can annotate on top of an NSImageView.

How to bring an NSImageView to the front or back of another NSImageView?

What you are asking about, I think, is how to control the z-order of views.

For historical performance reasons this is not well supported in AppKit (unlike UIKit in iOS), since until somewhat recently you couldn't actually have sibling views that overlap.

A common approach to this (on recent OS X releases) is to use Core Animation (in particular, CALayer) which does support z-ordering natively, but this is probably overkill for what you need (and in any event is going to have a learning curve for you).

What are you actually trying to do? Are these images (image views) precisely on top of one another? If so, the easiest (and much better performing) approach is to have a single NSImageView and to just send -setImage:... to it to change the displayed image.

NSImageView image aspect fill?

You may find it much easier to subclass NSView and provide a CALayer that does the aspect fill for you. Here is what the init might look like for this NSView subclass.

- (id)initWithFrame:(NSRect)frame andImage:(NSImage*)image
{
  self = [super initWithFrame:frame];
  if (self) {
    self.layer = [[CALayer alloc] init];
    self.layer.contentsGravity = kCAGravityResizeAspectFill;
    self.layer.contents = image;
    self.wantsLayer = YES;
  }
  return self;
}

Note that the order of setting the layer, then settings wantsLayer is very important (if you set wantsLayer first, you'll get a default backing layer instead).

You could have a setImage method that simply updates the contents of the layer.

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