[英]How to fix the Gradient on text when using an image in swift, as the gradient restarts
我正在尝试在文本上创建渐变,我使用UIGraphics来使用渐变图像来创建它。 我遇到的问题是渐变正在重新启动。 有谁知道如何缩放渐变以拉伸到文本?
文本在线框上,将被更改几次。 有时它会很完美但有时则不是。
渐变应该从黄色变为蓝色但重新开始,请参见下面的照片:
import UIKit
func colourTextWithGrad(label: UILabel) {
UIGraphicsBeginImageContext(label.frame.size)
UIImage(named: "testt.png")?.drawInRect(label.bounds)
let myGradient: UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
label.textColor = UIColor(patternImage: myGradient)
}
这是因为图案化的UIColor
只能进行平铺。 从文档 :
在绘制期间,图案颜色中的图像根据需要平铺以覆盖给定区域。
因此,当标签的边界发生变化时,您需要自己更改图像大小 - 因为图案图像不支持拉伸。 为此,您可以UILabel
,并覆盖layoutSubviews
方法。 这样的事情应该达到预期的效果:
class GradientLabel: UILabel {
let gradientImage = UIImage(named:"gradient.png")
override func layoutSubviews() {
guard let grad = gradientImage else { // skip re-drawing gradient if it doesn't exist
return
}
// redraw your gradient image
UIGraphicsBeginImageContext(frame.size)
grad.drawInRect(bounds)
let myGradient = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
// update text color
textColor = UIColor(patternImage: myGradient)
}
}
虽然值得注意的是我总是喜欢自己画一个渐变 - 因为你可以有更大的灵活性(比如说你想稍后添加另一种颜色)。 当您以不同的尺寸重绘图像时,图像的质量可能会降低(尽管由于渐变的性质,这应该是相当小的)。
您可以通过覆盖UILabel
子类的drawRect
来简单地绘制自己的渐变。 例如:
override func drawRect(rect: CGRect) {
// begin new image context to let the superclass draw the text in (so we can use it as a mask)
UIGraphicsBeginImageContextWithOptions(bounds.size, false, 0.0)
do {
// get your image context
let ctx = UIGraphicsGetCurrentContext()
// flip context
CGContextScaleCTM(ctx, 1, -1)
CGContextTranslateCTM(ctx, 0, -bounds.size.height)
// get the superclass to draw text
super.drawRect(rect)
}
// get image and end context
let img = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
// get drawRect context
let ctx = UIGraphicsGetCurrentContext()
// clip context to image
CGContextClipToMask(ctx, bounds, img.CGImage)
// define your colors and locations
let colors = [UIColor.orangeColor().CGColor, UIColor.redColor().CGColor, UIColor.purpleColor().CGColor, UIColor.blueColor().CGColor]
let locs:[CGFloat] = [0.0, 0.3, 0.6, 1.0]
// create your gradient
let grad = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), colors, locs)
// draw gradient
CGContextDrawLinearGradient(ctx, grad, CGPoint(x: 0, y:bounds.size.height*0.5), CGPoint(x:bounds.size.width, y:bounds.size.height*0.5), CGGradientDrawingOptions(rawValue: 0))
}
输出:
class GradientLabel: UILabel {
// MARK: - Colors to create gradient from
@IBInspectable open var gradientFrom: UIColor?
@IBInspectable open var gradientTo: UIColor?
override func draw(_ rect: CGRect) {
// begin new image context to let the superclass draw the text in (so we can use it as a mask)
UIGraphicsBeginImageContextWithOptions(bounds.size, false, 0.0)
do {
// get your image context
guard let ctx = UIGraphicsGetCurrentContext() else { super.draw(rect); return }
// flip context
ctx.scaleBy(x: 1, y: -1)
ctx.translateBy(x: 0, y: -bounds.size.height)
// get the superclass to draw text
super.draw(rect)
}
// get image and end context
guard let img = UIGraphicsGetImageFromCurrentImageContext(), img.cgImage != nil else { return }
UIGraphicsEndImageContext()
// get drawRect context
guard let ctx = UIGraphicsGetCurrentContext() else { return }
// clip context to image
ctx.clip(to: bounds, mask: img.cgImage!)
// define your colors and locations
let colors: [CGColor] = [UIColor.orange.cgColor, UIColor.red.cgColor, UIColor.purple.cgColor, UIColor.blue.cgColor]
let locs: [CGFloat] = [0.0, 0.3, 0.6, 1.0]
// create your gradient
guard let grad = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: colors as CFArray, locations: locs) else { return }
// draw gradient
ctx.drawLinearGradient(grad, start: CGPoint(x: 0, y: bounds.size.height*0.5), end: CGPoint(x:bounds.size.width, y: bounds.size.height*0.5), options: CGGradientDrawingOptions(rawValue: 0))
}
}
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