An object that stores color data and sometimes opacity.
- iOS 2.0+
- tvOS 9.0+
- watchOS 2.0+
Color objects can be created in a variety of ways:
UIKit provides standard system colors for matching the colors in your own UI objects to those provided by UIKit. You can reproduce these colors without needing to understand the underlying representation of color. See UI Element Colors.
UIKit provides definitions for standard colors such as red, orange, yellow, and so on. See Standard Colors.
You can create a custom color in a Core Graphics color space. See Creating a Color from Component Values.
You can create a color object from another object, such as another
UIColorobject, a Core Graphics representation of a color, or a Core Image color. See Creating a Color from Another Color Object.
The most common way to use a
UIColor object is to provide it to some other object in UIKit. For example, the
UIView class (and its descendants) include background and tint colors to affect how they are drawn onscreen. The following code example sets the background and tint color of a view.
When performing custom drawing, a
UIColor object provides methods that set the fill or stroke colors of the current graphics context. The following code example shows a simple example of custom drawing inside a view.
See Applying the Color to the Drawing Environment for the complete list of functions.
Understand Color Space Usage
UIColor object typically stores its color value as a Core Graphics color (
CGColor) in a Core Graphics color space (
CGColor). There are methods and properties that return the underlying color data, which are described in Getting the Color Information. When creating a custom color, the underlying color space and the range of values for each color component vary based on the iOS version.
For apps linked against the iOS 9 SDK and earlier, or running on iOS 9 and earlier, colors use one of two color spaces:
These device color spaces correspond closely to the display characteristics of the sRGB color space. Component values within these color spaces are in the range
1. When you create a color, the color object clamps values to ensure they fit within this range.
For apps linked against the iOS 10 SDK or later, and running on iOS 10 or later, colors use the following extended color spaces:
In the extended color spaces,
UIColor does not clamp values to fit inside the color gamut, meaning that component values may be less than
0 or greater than
1. On an sRGB display, such colors are outside the gamut and will not be rendered accurately. However, the extended color spaces are useful when you want a pixel format and representation that other color spaces can be easily converted into. For example, you can still convert a color in the display P3 color space to an extended sRGB format, even if that color is not within the sRGB color gamut. When you convert such a color, some of its values will fall outside of the
1 range. However, the color still renders correctly on a device with a P3 display gamut.
When employing custom colors, use extended color spaces to store your color values. When you need to worry about representing that color as closely as possible in a specific color space, convert the color from the extended color space into the target color space.
Most developers have no need to subclass
UIColor. The only time it might be necessary is if you require support for additional color spaces or color models. If you do subclass, the properties and methods you add must be safe to use from multiple threads.