Create a template image

Save image as png and tell if it works.

No, it doesn't.

I'm following the book "App Development with Swift" by Apple, there is the link https://developer.apple.com/go/?id=app-dev-swift-student-swift-4 which envelop a pdf which works, even with small change to it, made with preview, it works.

But with a new pdf the "template image" doesn't works.

What do you mean by "template"?

In macOS, a template NSImage is one whose colors are ignored, and the only significant information is the opacity (transparency) of the pixels. When you specify a template image for a button, the button colorizes the image with a standard color suitable for the button state (normal, highlighted, etc). You can't control which color is used.

If you want that behavior, then you must specify that the image is a template, and there are two ways to do this:

1. Load the NSImage and set its isTemplate property to true.

2. Load the NSImage using NSImage(named:), and specify an image file name that ends in the word "Template" (e.g. "MyImage Template.pdf", which you load as NSImage(named:"MyImage Template")).

Note that if you're setting the image name for a button in IB, you can use technique #2 to get it to be a template.

Yes, I want a template, a black and white image which color can be changed using setTitleColor(_ color: UIColor?, for state: UIControl.State).

I tested QuinceyMorris case 1, loading the pdf provided by Apple in https://developer.apple.com/go/?id=app-dev-swift-student-swift-4 and setting in Interface Builder "Render As" Template Image". It works.

If I change the pdf I obtain a square completely filled with the color desired. But a uniform square, not the image.

Thanks QuinceyMorris, the point is opacity. My pdf were without alpha channel. I modified it, using Gimp, so the white parts became transparent and it works.