How to programatically create transparent NSImage?

Question

Very simple: How to programatically create transparent NSImage? Unless it is not so simple... Previous OSX versions gave NSImage transparent background by default when calling

let image = NSImage(size: size)

but now it has black background. How do I create a transparent one? I want to lockFocus() on atransparent image of given size it and and draw.

@JoshuaNozzi This is OSX question, not iOS! `UIIMage != NSImage` all libraries are different. — Rasto, Jul 15 '17 at 19:14
Do you mean to say `previous osx versions gave`? you mentioned iOS there. iOS has no NSImage. — adev, Jul 15 '17 at 19:22
@JoshuaNozzi @Adev Sorry that is a typo. Should have been `Previous OSX version`, not `previous iOS version` — Rasto, Jul 15 '17 at 19:30
You cannot create an invisible, transparent NSImage object under macOS 10.12 as the operating system places the diagonal semi-translucent symbol on it. — El Tomato, Jul 15 '17 at 22:19

Joshua Nozzi · Answer 1 · 2017-07-15T19:31:25.990

1

A few major Mac OS versions ago the lock/unlock focus methods, while not deprecated, have been deemphasized in favor of NSImage(size:flipped:drawingHandler:) for deferred drawing. I have personally encountered problems with unexpectedly-rasterized text and certain alpha channel problems when composing multiple images together into one using lock/unlock in apps linked against later macOS SDKs.

My first suggestion would be to use that method and see if that resolves the issue. Your drawing handler can simply contain return true.

edited Jul 15 '17 at 19:31

answered Jul 15 '17 at 19:23

Joshua Nozzi

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Was your issue where you were doing different types of compositing on one image...I'm having the strangest outputs. – Chris Aug 13 '18 at 13:38
@Chris Not sure if compositing had anything specifically to do with it, but as I said, the biggest problem was that text was always rasterized. It's been awhile so I can't remember exactly the problem with alpha but I believe it was probably text background issues. – Joshua Nozzi Aug 13 '18 at 18:09

How to programatically create transparent NSImage?

1 Answers1