例如,黑色的反色应该是白色。
---- 编辑 ----
根据 @amleszk 的回答,我更新了 UIColor 的扩展/类别,并添加了这个方法:
Swift
func inverseColor() -> UIColor {
var alpha: CGFloat = 1.0
var red: CGFloat = 0.0, green: CGFloat = 0.0, blue: CGFloat = 0.0
if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
return UIColor(red: 1.0 - red, green: 1.0 - green, blue: 1.0 - blue, alpha: alpha)
}
var hue: CGFloat = 0.0, saturation: CGFloat = 0.0, brightness: CGFloat = 0.0
if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {
return UIColor(hue: 1.0 - hue, saturation: 1.0 - saturation, brightness: 1.0 - brightness, alpha: alpha)
}
var white: CGFloat = 0.0
if self.getWhite(&white, alpha: &alpha) {
return UIColor(white: 1.0 - white, alpha: alpha)
}
return self
}
Objective-C
- (UIColor *)inverseColor {
CGFloat alpha;
CGFloat red, green, blue;
if ([self getRed:&red green:&green blue:&blue alpha:&alpha]) {
return [UIColor colorWithRed:1.0 - red green:1.0 - green blue:1.0 - blue alpha:alpha];
}
CGFloat hue, saturation, brightness;
if ([self getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
return [UIColor colorWithHue:1.0 - hue saturation:1.0 - saturation brightness:1.0 - brightness alpha:alpha];
}
CGFloat white;
if ([self getWhite:&white alpha:&alpha]) {
return [UIColor colorWithWhite:1.0 - white alpha:alpha];
}
return nil;
}
---- 已弃用 ----
根据@grc的答案,我创建了一个UIColor类别,并使用以下方法:
- (UIColor *)inverseColor {
CGColorRef oldCGColor = self.CGColor;
int numberOfComponents = CGColorGetNumberOfComponents(oldCGColor);
// can not invert - the only component is the alpha
// e.g. self == [UIColor groupTableViewBackgroundColor]
if (numberOfComponents == 1) {
return [UIColor colorWithCGColor:oldCGColor];
}
const CGFloat *oldComponentColors = CGColorGetComponents(oldCGColor);
CGFloat newComponentColors[numberOfComponents];
int i = numberOfComponents - 1;
newComponentColors[i] = oldComponentColors[i]; // alpha
while (--i >= 0) {
newComponentColors[i] = 1 - oldComponentColors[i];
}
CGColorRef newCGColor = CGColorCreate(CGColorGetColorSpace(oldCGColor), newComponentColors);
UIColor *newColor = [UIColor colorWithCGColor:newCGColor];
CGColorRelease(newCGColor);
return newColor;
}
iOS5+
-(UIColor*) inverseColor
{
CGFloat r,g,b,a;
[self getRed:&r green:&g blue:&b alpha:&a];
return [UIColor colorWithRed:1.-r green:1.-g blue:1.-b alpha:a];
}
这应该可以工作:
// oldColor is the UIColor to invert
const CGFloat *componentColors = CGColorGetComponents(oldColor.CGColor);
UIColor *newColor = [[UIColor alloc] initWithRed:(1.0 - componentColors[0])
green:(1.0 - componentColors[1])
blue:(1.0 - componentColors[2])
alpha:componentColors[3]];
一种流行的做法是扩展 UIColor 类:
extension UIColor {
func inverse () -> UIColor {
var r:CGFloat = 0.0; var g:CGFloat = 0.0; var b:CGFloat = 0.0; var a:CGFloat = 0.0;
if self.getRed(&r, green: &g, blue: &b, alpha: &a) {
return UIColor(red: 1.0-r, green: 1.0 - g, blue: 1.0 - b, alpha: a)
}
return .black // Return a default colour
}
}
Swift解决方案扩展UIColor
,添加一个计算属性inverted
:
extension UIColor {
var inverted: UIColor {
var a: CGFloat = 0.0, r: CGFloat = 0.0, g: CGFloat = 0.0, b: CGFloat = 0.0
return getRed(&r, green: &g, blue: &b, alpha: &a) ? UIColor(red: 1.0-r, green: 1.0-g, blue: 1.0-b, alpha: a) : .black
}
}
可用于任何 UIColor
实例(.red
、.blue
、.white
等),例如:
view.backgroundColor = UIColor.blue.inverted //Results in yellow background
view.backgroundColor = UIColor.black.inverted //Results in white background
GRC的解决方案存在一个问题:CGColorGetComponents返回的是0.0-1.0的比例,而不是2-255。因此,你应该使用
UIColor *newColor = [[UIColor alloc] initWithRed:(1.0 - componentColors[0])
green:(1.0 - componentColors[1])
blue:(1.0 - componentColors[2])
alpha:componentColors[3]];
否则一切都会是白色(1.0及更高版本)
和amleszk使用的方式类似,这里也是用1.-color代替255。顺便说一下,那个1.代表的是浮点数1.0,应该写成1.0而不是1.,以避免混淆。
对于所有来到这里寻找答案的Swifters,为了帮助您,以下是使用Swift应该看起来的样子:
func inverseColor(color: UIColor) -> UIColor{
var a: CGFloat = 0.0; var r: CGFloat = 0.0; var g: CGFloat = 0.0; var b: CGFloat = 0.0;
color.getRed(&r, green: &g, blue: &b, alpha: &a);
return UIColor(red: -r, green: -g, blue: -b, alpha: a);
}
我使用了Dade的答案并稍微调整了一下,因为我正在寻找一种漂亮的方式来计算给定背景颜色的文本前景色。
因此,如果您想要获得给定背景颜色的漂亮文本颜色,我建议您这样做。它会给出您所给定背景颜色中最亮的颜色:
extension UIColor {
func maxBright() -> UIColor {
var r:CGFloat = 0.0; var g:CGFloat = 0.0; var b:CGFloat = 0.0; var a:CGFloat = 0.0;
if self.getRed(&r, green: &g, blue: &b, alpha: &a) {
let d:CGFloat = 1.0 - max(r,g,b)
return UIColor(red: r + d, green: g + d , blue: b + d, alpha: 1.0)
}
return self
}
}
它的工作方式就像将RGB滑块向上滑动,直到最亮的组件达到最大值。
例如:
titleLable.backgroundColor = UIColor.blackColor()
titleLabel.textColor = titleLabel.backgroundColor?.maxBright()
将会给你一个黑底白字的标签。尝试其他颜色,你会看到有趣的结果 :)
这可能不是你想要的,但它确实为文本前/后景色提供了有趣的结果。
只是分享一下
你没有得到灰色的反色。所以当你使用灰色背景和其反色作为文本颜色时,就会出现这种情况。
这个方法甚至适用于灰色,我只是在@iWills的代码中添加了一些额外的代码。
//====== TO GET THE OPPOSIT COLORS =====
-(UIColor *)reverseColorOf :(UIColor *)oldColor
{
CGColorRef oldCGColor = oldColor.CGColor;
int numberOfComponents = CGColorGetNumberOfComponents(oldCGColor);
// can not invert - the only component is the alpha
if (numberOfComponents == 1) {
return [UIColor colorWithCGColor:oldCGColor];
}
const CGFloat *oldComponentColors = CGColorGetComponents(oldCGColor);
CGFloat newComponentColors[numberOfComponents];
int i = numberOfComponents - 1;
newComponentColors[i] = oldComponentColors[i]; // alpha
while (--i >= 0) {
newComponentColors[i] = 1 - oldComponentColors[i];
}
CGColorRef newCGColor = CGColorCreate(CGColorGetColorSpace(oldCGColor), newComponentColors);
UIColor *newColor = [UIColor colorWithCGColor:newCGColor];
CGColorRelease(newCGColor);
//=====For the GRAY colors 'Middle level colors'
CGFloat white = 0;
[oldColor getWhite:&white alpha:nil];
if(white>0.3 && white < 0.67)
{
if(white >= 0.5)
newColor = [UIColor darkGrayColor];
else if (white < 0.5)
newColor = [UIColor blackColor];
}
return newColor;
}