iOS-绘制渐变-Swift

  func yellowGradientImage（bounds：CGRect）-> UIImage 
 {
 let gradientLayer = CAGradientLayer（）
 gradientLayer.colors = [UIColor（红色：（202 / 255.0），绿色：（197 / 255.0），蓝色：（52 / 255.0） ，alpha：1.0）.CGColor，UIColor（红色：（253 / 255.0），绿色：（248 / 255.0），蓝色：（101 / 255.0），alpha：1.0）。CGColor] 
 gradientLayer.bounds = bounds 
 UIGraphicsBeginImageContextWithOptions（gradientLayer.bounds.size，true，0.0）
 let context = UIGraphicsGetCurrentContext（）
 gradientLayer.renderInContext（context！）
 let image = UIGraphicsGetImageFromCurrentImageContext（）
 UIGraphicsEndImageContext（）
返回图像
}

将渐变应用于文本接下来，您需要使用 UIColor（patternImage：...）使用返回为 textColor 的图像。例如：

  let label = UILabel（）
 label.font = UIFont.systemFontOfSize（150.0）
 label.text = HELLO WORLD 
 label.sizeToFit（）
 
 let image = yellowGradientImage（label.bounds）
 label.textColor = UIColor（patternImage：image）

其结果是：

swift 3.0：

  func yellowGradientImage（bounds：CGRect）-> UIImage 
 {
 let gradientLayer = CAGradientLayer（）
 gradientLayer.colors = [UIColor（红色：（202 / 255.0），绿色：（197 / 255.0），蓝色：（52 / 255.0） ，alpha：1.0）.cgColor，UIColor（红色：（253 / 255.0），绿色：（248 / 255.0），蓝色：（101 / 255.0），alpha：1.0）.cgColor] 
 gradientLayer.bounds = bounds 
 UIGraphicsBeginImageContextWithOptions（gradientLayer.bounds.size，true，0.0）
 let context = UIGraphicsGetCurrentContext（）
 gradientLayer.render（in：context！）
 let image = UIGraphicsGetImageFromCurrentImageContext（）
 UIGraphicsEndImageContext（）
返回图像！ 
} 
 
让label = UILabel（）
 label.font = UIFont.systemFont（ofSize：150.0）
 label.text = HELLO WORLD 
 label.sizeToFit（）
 
 let image = yellowGradientImage（bounds：label.bounds）
 label.textColor = UIColor（patternImage：image）

I'm trying to draw a gradient to UILabel, but it draws only the colors I can't see the text.I saw the code from here StackOverflow

my modification:

extension String{
    func gradient(x:CGFloat,y:CGFloat, fontSize:CGFloat)->UIImage{
        let font:UIFont = UIFont.systemFontOfSize(fontSize)
        let name:String = NSFontAttributeName
        let textSize: CGSize = self.sizeWithAttributes([name:font])
        let width:CGFloat = textSize.width         // max 1024 due to Core Graphics limitations
        let height:CGFloat = textSize.height       // max 1024 due to Core Graphics limitations
        UIGraphicsBeginImageContext(CGSizeMake(width, height))
        let context = UIGraphicsGetCurrentContext()
        UIGraphicsPushContext(context!)
        //draw gradient
        let glossGradient:CGGradientRef?
        let rgbColorspace:CGColorSpaceRef?
        let num_locations:size_t = 2
        let locations:[CGFloat] = [ 0.0, 1.0 ]
        let components:[CGFloat] = [(202 / 255.0), (197 / 255.0), (52 / 255.0), 1.0,  // Start color
            (253 / 255.0), (248 / 255.0), (101 / 255.0), 1.0] // End color
        rgbColorspace = CGColorSpaceCreateDeviceRGB()
        glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations)
        let topCenter = CGPointMake(0, 0);
        let bottomCenter = CGPointMake(0, textSize.height);
        CGContextDrawLinearGradient(context, glossGradient, topCenter, bottomCenter, CGGradientDrawingOptions.DrawsBeforeStartLocation)
        UIGraphicsPopContext()
        let gradientImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return  gradientImage
    }
}

and the setup of the imageView

    self.timeLeftIV = UIImageView(frame: CGRectMake(self.pyramidFakeView.frame.origin.x/2-25,0, 100,20))
    self.timeLeftIV.image = "59:48".gradient(timeLeftIV.frame.origin.x, y: timeLeftIV.frame.origin.y, fontSize: 6.0)

the result of the code:

解决方案

There is an easier way of getting a gradient as a UIImage. You can use a CAGradientLayer. For example:

func yellowGradientImage(bounds:CGRect) -> UIImage
{
    let gradientLayer = CAGradientLayer()
    gradientLayer.colors = [UIColor(red: (202 / 255.0), green: (197 / 255.0), blue: (52 / 255.0), alpha: 1.0).CGColor, UIColor(red: (253 / 255.0), green: (248 / 255.0), blue: (101 / 255.0), alpha: 1.0).CGColor]
    gradientLayer.bounds = bounds
    UIGraphicsBeginImageContextWithOptions(gradientLayer.bounds.size, true, 0.0)
    let context = UIGraphicsGetCurrentContext()
    gradientLayer.renderInContext(context!)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
}

To apply the gradient to text you next need to use the image returned as the textColor using UIColor(patternImage: ...). For example:

let label = UILabel()
label.font = UIFont.systemFontOfSize(150.0)
label.text = "HELLO WORLD"
label.sizeToFit()

let image = yellowGradientImage(label.bounds)
label.textColor = UIColor(patternImage: image)

Which results in:

swift 3.0:

func yellowGradientImage(bounds:CGRect) -> UIImage
{
    let gradientLayer = CAGradientLayer()
    gradientLayer.colors = [UIColor(red: (202 / 255.0), green: (197 / 255.0), blue: (52 / 255.0), alpha: 1.0).cgColor, UIColor(red: (253 / 255.0), green: (248 / 255.0), blue: (101 / 255.0), alpha: 1.0).cgColor]
    gradientLayer.bounds = bounds
    UIGraphicsBeginImageContextWithOptions(gradientLayer.bounds.size, true, 0.0)
    let context = UIGraphicsGetCurrentContext()
    gradientLayer.render(in: context!)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image!
}

let label = UILabel()
label.font = UIFont.systemFont(ofSize: 150.0)
label.text = "HELLO WORLD"
label.sizeToFit()

let image = yellowGradientImage(bounds: label.bounds)
label.textColor = UIColor(patternImage: image)

这篇关于iOS-绘制渐变-Swift的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

08-03 23:17