从UIColor中提取rgb

Question

之前看到这个问过,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,也考虑到非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

感谢威尔斯特的方向.对于那些使用灰度颜色(使用colorWithWhite:alpha:)创建的人,下面的代码示例将让您找出白色值(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];
    }
}