Convert NSColor to RGB - objective-c

Question

I'm trying to convert an NSColor to RGB, but it seems to give an entirely incorrect result:
NSColor *testColor = [NSColor colorWithCalibratedWhite:0.65 alpha:1.0];
const CGFloat* components = CGColorGetComponents(testColor.CGColor);
NSLog(#"Red: %f", components[0]);
NSLog(#"Green: %f", components[1]);
NSLog(#"Blue: %f", components[2]);
NSLog(#"Alpha: %f", CGColorGetAlpha(testColor.CGColor));
I get back : red = 0.65 - green = 1.0 - blue = 0.0 and alpha is 1.0 - which results in an entirely different color. (It should be gray, now it's green).
Am I doing something wrong?

Answer 1

Extracting RGBA values from NSColor: (Swift 3)
let nsColor: NSColor = .red
let ciColor: CIColor = .init(color: nsColor)!
print(ciColor.red) // 1.0
print(ciColor.green) // 0.0
print(ciColor.blue) // 0.0
print(ciColor.alpha) // 1.0 // Or use nsColor.alphaComponent
NOTE: NSColor.blackColor().redComponent will crash the app, but the above code won't

Answer 2

I had the same problem when I wanted to convert a picked color to hexadecimal. NSColor components values was not correct. I managed to resolve my problem with your comment above.
Example in Swift:
let colorTest = NSColor.init(calibratedWhite: 0.65, alpha: 1.0)
let color = colorTest.usingColorSpace(NSColorSpace.deviceRGB) ?? colorTest
print(colorTest)
// NSCalibratedWhiteColorSpace 0.65 1
print(colorTest.colorSpace)
// Generic Gray colorspace
print("red: \(color.redComponent) green:\(color.greenComponent) blue:\(color.blueComponent)")
// red: 0.708725869655609 green:0.708725869655609 blue:0.708725869655609

Answer 3

You need to convert the color to an RGB color space using an NSColorSpace object first, then you can get the components using the various NSColor accessor methods

Answer 4

For a NSColor * color
CGFloat red = [color redComponent];
CGFloat green = [color greenComponent];
CGFloat blue = [color blueComponent];

Answer 5

I have used this in the past, and it worked for me.
NSColorSpace *colorSpace = [NSColorSpace sRGBColorSpace];
NSColor *testColor = [NSColor colorWithColorSpace:colorSpace components:SRGB];
CGFloat red = [testColor redComponent];
CGFloat green = [testColor greenComponent];
CGFloat blue = [testColor blueComponent];

Answer 6

You have to check the colorspace first
then if it's rgb you can use
CGFloat red = [testColor redComponent];
...
For grayscale you have to convert it differently
CGFloat red = [testColor whiteComponent];
CGFloat blue = [testColor whiteComponent];
CGFloat green = [testColor whiteComponent];

Answer 7

Here’s a safe Swift 5 SKColor extension for getting the RGB components of an NSColor or UIColor. (Note SKColor is just a typealias for one or the other based on the platform.)
public extension SKColor {
var sRGBAComponents: (red: CGFloat , green: CGFloat, blue: CGFloat, alpha: CGFloat) {
#if os(iOS)
let rgbColor = self // lolz no color conversion on iOS, but on iOS it'll respond to getRed(...) anyhow
#elseif os(macOS)
let rgbColor = usingColorSpace(.extendedSRGB) ?? SKColor(red: 1, green: 1, blue: 1, alpha: 1) // will return 'self' if already RGB
#endif
var red: CGFloat = 0, green: CGFloat = 0, blue: CGFloat = 0, alpha: CGFloat = 0
rgbColor.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
return (red: red, green: green, blue: blue, alpha: alpha)
}
}