Can I mix two UIColor together?

Question

I have colorA which is [UIColor blueColor], and colorB, which is [UIColor redColor]. Is this possible for me to render a [UIColor purple]? How can it be implemented? Thanks.

Answer 1

Inelegant, but it works:

UIColor* blend( UIColor* c1, UIColor* c2, float alpha )
{
    alpha = MIN( 1.f, MAX( 0.f, alpha ) );
    float beta = 1.f - alpha;
    CGFloat r1, g1, b1, a1, r2, g2, b2, a2;
    [c1 getRed:&r1 green:&g1 blue:&b1 alpha:&a1];
    [c2 getRed:&r2 green:&g2 blue:&b2 alpha:&a2];
    CGFloat r = r1 * beta + r2 * alpha;
    CGFloat g = g1 * beta + g2 * alpha;
    CGFloat b = b1 * beta + b2 * alpha;
    return [UIColor colorWithRed:r green:g blue:b alpha:1.f];
}

More elegant:

UIColor+Extensions.h:

@interface UIColor (Extensions)

- (UIColor*)blendWithColor:(UIColor*)color2 alpha:(CGFloat)alpha2;

@end

UIColor+Extensions.m:

@implementation UIColor (Extensions)

- (UIColor*)blendWithColor:(UIColor*)color2 alpha:(CGFloat)alpha2
{
    alpha2 = MIN( 1.0, MAX( 0.0, alpha2 ) );
    CGFloat beta = 1.0 - alpha2;
    CGFloat r1, g1, b1, a1, r2, g2, b2, a2;
    [self getRed:&r1 green:&g1 blue:&b1 alpha:&a1];
    [color2 getRed:&r2 green:&g2 blue:&b2 alpha:&a2];
    CGFloat red     = r1 * beta + r2 * alpha2;
    CGFloat green   = g1 * beta + g2 * alpha2;
    CGFloat blue    = b1 * beta + b2 * alpha2;
    CGFloat alpha   = a1 * beta + a2 * alpha2;
    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}

@end

Swift 3/4:

extension UIColor
{
func mixin(infusion:UIColor, alpha:CGFloat) -> UIColor {
    let alpha2 = min(1.0, max(0, alpha))
    let beta = 1.0 - alpha2

    var r1:CGFloat = 0, r2:CGFloat = 0
    var g1:CGFloat = 0, g2:CGFloat = 0
    var b1:CGFloat = 0, b2:CGFloat = 0
    var a1:CGFloat = 0, a2:CGFloat = 0
    if getRed(&r1, green: &g1, blue: &b1, alpha: &a1) &&
        infusion.getRed(&r2, green: &g2, blue: &b2, alpha: &a2)
    {
        let red     = r1 * beta + r2 * alpha2;
        let green   = g1 * beta + g2 * alpha2;
        let blue    = b1 * beta + b2 * alpha2;
        let alpha   = a1 * beta + a2 * alpha2;
        return UIColor(red: red, green: green, blue: blue, alpha: alpha)
    }
    // epique de las failuree
    return self
}
}

Answer 2

Ask each input color for its RGBA components using -[UIColor getRed:green:blue:alpha:]. Average the components from each, and create a new color using +[UIColor colorWithRed:green:blue:alpha:].

Answer 3

Swift5 UIColor Extension

extension UIColor {
    func add(_ overlay: UIColor) -> UIColor {
        var bgR: CGFloat = 0
        var bgG: CGFloat = 0
        var bgB: CGFloat = 0
        var bgA: CGFloat = 0
        
        var fgR: CGFloat = 0
        var fgG: CGFloat = 0
        var fgB: CGFloat = 0
        var fgA: CGFloat = 0
        
        self.getRed(&bgR, green: &bgG, blue: &bgB, alpha: &bgA)
        overlay.getRed(&fgR, green: &fgG, blue: &fgB, alpha: &fgA)
        
        let r = fgA * fgR + (1 - fgA) * bgR
        let g = fgA * fgG + (1 - fgA) * bgG
        let b = fgA * fgB + (1 - fgA) * bgB
        
        return UIColor(red: r, green: g, blue: b, alpha: 1.0)
    }
    
    static func +(lhs: UIColor, rhs: UIColor) -> UIColor {
        return lhs.add(rhs)
    }
}

Usage

let opacity: CGFloat = 0.6
let start = UIColor.red
let end = UIColor.blue
let combined = start.withAlphaComponent(opacity) + end.withAlphaComponent(1-opacity)

Answer 4

Since it is 2020 now, and we have "Dark Mode" available, many "colours" are not just colours anymore, but automatically adapt to color changes. They are created by calling UIColor(dynamicProvider: ...).

You should check if both colors are dynamic colors, and if they are, return a dynamic color. Mixing one dynamic color and a non-dynamic color doesn't really make sense, so in that case return a non-dynamic color.

Answer 5

You can't mix two UIColors directly as you mention in your question. Anyways there is an example to mix two colors using other schemes. The link for same is as follows:

Link Here

Answer 6

If you want to use purple color then its not a big deal.All the UIColor are rgb color.You can simply pass the RGB value for each color and can get the desired color.Use this link to convert hex value of any color to convert in UIColor. http://www.touch-code-magazine.com/web-color-to-uicolor-convertor/

like #color code for green is #008400: [UIColor colorWithRed:0 green:0.518 blue:0 alpha:1] /#008400/