NSColorPanel to hex issue? - nscolor

Question

I have an NSColorPanel that I am inputting RGV values:
NSColorPanel * sharedPanel = [NSColorPanel sharedColorPanel];
[sharedPanel setTarget: self];
[sharedPanel setAction: updateColor:];
[sharedPanel orderFront: self];
The color panel display and I set this value: r66, g114, b170
By my calculations, this should be #4272AA. I use the following code to convert to hex:
- (void) updateColor: (NSColorPanel*) panel
{
NSString * hexString = [panel.color hexadecimalValueOfAnNSColor];
NSLog(#"%#", hexString);
}
Which logs out #345d9a (not what I would expect).
I'm using the following method from directly from developer.apple.com to convert the color to hex:
#import <Cocoa/Cocoa.h>
#interface NSColor(NSColorHexadecimalValue)
-(NSString *)hexadecimalValueOfAnNSColor;
#end
#implementation NSColor(NSColorHexadecimalValue)
-(NSString *)hexadecimalValueOfAnNSColor
{
float redFloatValue, greenFloatValue, blueFloatValue;
int redIntValue, greenIntValue, blueIntValue;
NSString *redHexValue, *greenHexValue, *blueHexValue;
//Convert the NSColor to the RGB color space before we can access its components
NSColor *convertedColor=[self colorUsingColorSpaceName:NSCalibratedRGBColorSpace];
if(convertedColor)
{
// Get the red, green, and blue components of the color
[convertedColor getRed:&redFloatValue green:&greenFloatValue blue:&blueFloatValue alpha:NULL];
// Convert the components to numbers (unsigned decimal integer) between 0 and 255
redIntValue=redFloatValue*255.99999f;
greenIntValue=greenFloatValue*255.99999f;
blueIntValue=blueFloatValue*255.99999f;
// Convert the numbers to hex strings
redHexValue=[NSString stringWithFormat:#"%02x", redIntValue];
greenHexValue=[NSString stringWithFormat:#"%02x", greenIntValue];
blueHexValue=[NSString stringWithFormat:#"%02x", blueIntValue];
// Concatenate the red, green, and blue components' hex strings together with a "#"
return [NSString stringWithFormat:#"#%#%#%#", redHexValue, greenHexValue, blueHexValue];
}
return nil;
}
#end
Any suggestions as to what I'm doing wrong?

Answer 1

You must have entered coordinates in different color space (probably device's, since on my Mac, #4272AA in color space of my display when converted to calibrated color space produces almost the same result, #345C9A).
To change color space in NSColorPanel, click tiny rainbow button. NSCalibratedRGBColorSpace corresponds to "Generic RGB" selection — since your get-hex method uses calibrated, you need to use the same if you want to get the same numbers back.
A tiny bit of warning: this piece of code from developer.apple.com is harmful.
When people say hex codes to each other, it is almost universally assumed to mean the same color as HTML/CSS would produce. This means hex codes must be in sRGB color space, since web standards dictate to use sRGB whenever color space information is omitted/missing.
Apple's "Generic RGB" (NSCalibratedRGBColorSpace) is very different from sRGB and native color spaces of most modern displays. Your problem just demonstrates how huge that difference is.
Most of displays in the world are manufactured to match sRGB as best as possible, and high quality displays of modern Apple's devices are particularly good at that.
This leads to somewhat surprising conclusion: if need those hex codes to produce same colors as in HTML, using NSDeviceRGBColorSpace, however wrong that is, instead of NSCalibratedRGBColorSpace gives much better results. You can easily verify that fact by entering the same color coordinates in Device, Generic and sRGB color spaces and comparing to what HTML page in Safari produces.
If you need correct and guaranteed match with hex codes used in Web, you will have to do color conversion to sRGB manually, since NSColor does not support reading components for any color profiles other than Device RGB and Calibrated RGB.