在iOS上插入渐变颜色(与NSGradient一样)?

时间:2013-12-02 07:45:28

标签: ios objective-c gradient appkit nsgradient

AppKit在iOS中不可用,所以我一直在寻找替代品。

具体来说,我正在寻找替代方法:

- (NSColor *)interpolatedColorAtLocation: (CGFloat)location

我需要一种方法来定义渐变,并根据输入位置(float)查找颜色值。

2 个答案:

答案 0 :(得分:4)

如果你真的需要一个渐变对象(用于绘制渐变?),你可以使用CG级CGGradient“类”。

至于在渐变中的特定位置插入颜色,您需要知道的是两个周围的颜色(相对于您的给定位置)以及它们之间的插值(t将是{之间的位置} {1}}相对于两种颜色,而不是整个渐变):

0.0..1.0

使用示例:

- (UIColor *)colorByInterpolatingWith:(UIColor *)color factor:(CGFloat)factor {
    factor = MIN(MAX(t, 0.0), 1.0);

    const CGFloat *startComponent = CGColorGetComponents(self.CGColor);
    const CGFloat *endComponent = CGColorGetComponents(color.CGColor);

    float startAlpha = CGColorGetAlpha(self.CGColor);
    float endAlpha = CGColorGetAlpha(color.CGColor);

    float r = startComponent[0] + (endComponent[0] - startComponent[0]) * factor;
    float g = startComponent[1] + (endComponent[1] - startComponent[1]) * factor;
    float b = startComponent[2] + (endComponent[2] - startComponent[2]) * factor;
    float a = startAlpha + (endAlpha - startAlpha) * factor;

    return [UIColor colorWithRed:r green:g blue:b alpha:a];
}

答案 1 :(得分:0)

Swift版本(macOS)

这种颜色插值可以通过简单的线来实现:

let color = NSColor.green.interpolate(.blue, 0.5)

将此扩展程序添加到您的项目中:

   extension NSColor{
    /**
     * Interpolates between two NSColors
     * EXAMPLE: NSColor.green.interpolate(.blue, 0.5)
     * NOTE: There is also a native alternative: NSColor.green.blended(withFraction: 0.5, of: .blue)
     */
    func interpolate(_ to:NSColor,_ scalar:CGFloat)->NSColor{
        func interpolate(_ start:CGFloat,_ end:CGFloat,_ scalar:CGFloat)->CGFloat{
            return start + (end - start) * scalar
        }
        let fromRGBColor:NSColor = self.usingColorSpace(.genericRGB)!
        let toRGBColor:NSColor = to.usingColorSpace(.genericRGB)!
        let red:CGFloat = interpolate(fromRGBColor.redComponent, toRGBColor.redComponent,scalar)
        let green:CGFloat = interpolate(fromRGBColor.greenComponent, toRGBColor.greenComponent,scalar)
        let blue:CGFloat = interpolate(fromRGBColor.blueComponent, toRGBColor.blueComponent,scalar)
        let alpha:CGFloat = interpolate(fromRGBColor.alphaComponent, toRGBColor.alphaComponent,scalar)
        return NSColor.init(red: red, green: green, blue: blue, alpha: alpha)
    }
}

通过此扩展和AnimLib

获得了波纹管动画

enter image description here