Question

之前看过这个问题，但我的例子似乎没有用。

const CGFloat *toCol = CGColorGetComponents([[UIColor greenColor] CGColor]);

使用GDB查看数组是空的。任何提示？

Answer 1

您提供的代码示例应该有效。

试试这个：

UIColor uicolor = [[UIColor greenColor] retain];
CGColorRef color = [uicolor CGColor];

int numComponents = CGColorGetNumberOfComponents(color);

if (numComponents == 4)
{
  const CGFloat *components = CGColorGetComponents(color);
  CGFloat red = components[0];
  CGFloat green = components[1];
  CGFloat blue = components[2];
  CGFloat alpha = components[3];
}

[uicolor release];

Answer 2

在iOS 5中，您可以使用：

UIColor *color = [UIColor orangeColor];
CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0;

if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
    [color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
    const CGFloat *components = CGColorGetComponents(color.CGColor);
    red = components[0];
    green = components[1];
    blue = components[2];
    alpha = components[3];
}

Answer 3

这是一个全面的解决方案，也考虑了非RGB颜色，例如[UIColor blackColor]

UIColor *color = [UIColor blackColor];
CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0;
// iOS 5
if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
     [color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
     // < iOS 5
     const CGFloat *components = CGColorGetComponents(color.CGColor);
     red = components[0];
     green = components[1];
     blue = components[2];
     alpha = components[3];
}

// This is a non-RGB color
if(CGColorGetNumberOfComponents(color.CGColor) == 2) {
    CGFloat hue;
    CGFloat saturation;
    CGFloat brightness;
    [color getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];

}

Answer 4

只需使用memcpy：

CGColorRef tmpColor = [[currentColorView backgroundColor] CGColor];
CGFloat newComponents[4] = {};
memcpy(newComponents, CGColorGetComponents(tmpColor), sizeof(newComponents));
// now newComponents is filled with tmpColor rgba data

Answer 5

感谢威尔斯特的指示。对于任何使用灰度颜色的人（使用colorWithWhite:alpha:创建），下面的代码示例将让您计算出白色值（HSV方法不适用于以这种方式创建的颜色）。

CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0, white = 0.0;

// This is a non-RGB color
if(CGColorGetNumberOfComponents(self.color.CGColor) == 2) {
    [self.color getWhite:&white alpha:&alpha];
}
else {
    // iOS 5
    if ([self.color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
        [self.color getRed:&red green:&green blue:&blue alpha:&alpha];
    } else {
        // < iOS 5
        const CGFloat *components = CGColorGetComponents(self.color.CGColor);
        red = components[0];
        green = components[1];
        blue = components[2];
        alpha = components[3];
    }
}

Answer 6

本文帮助我解决了这个问题，或者至少构建了解决它的框架。

http://developer.apple.com/iphone/library/qa/qa2007/qa1509.html

Answer 7

这里有一些更直接的示例代码，用于从任意颜色中获取RGB组件：

Get RGB value from UIColor presets

Answer 8

结帐uicolor-utilities。看起来像是一个非常好的库，用于执行此操作以及UIColor的许多其他有用的东西。例如，使用此库，您可以编写：

CGFloat red = [myColor red];

从UIColor中提取rgb

8 个答案: