平滑地应用渐变到UIImage [英] Applying Gradient to UIImage Smoothly

查看:98
本文介绍了平滑地应用渐变到UIImage的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我正在尝试使用CoreGraphic将渐变应用于UIImage;但是,我得到的结果并不是很好。我想在图像的底部创建一个黑色到透明的渐变,为我创建一个对比,让我放置一些文本。然而,我能够的渐变与图像不能很好地融合; 您可以清楚地看到中心的分离。我正在寻找的结果就像这个应用程序: http://capptivate.co/2014 / 02/17 / yummly-3 /
我应该如何应用渐变来实现这一目标? (我必须将此应用于大量图像)。

I am trying to apply gradient to UIImage using CoreGraphic; however, the result I got is not very nice. I want to create a black to transparent gradient at the bottom of the image to create a contrast for me to place some text. However, the gradient I was able doesn't blend well with the image; you can clearly see the separation in the center. The result I am looking for is like this application: http://capptivate.co/2014/02/17/yummly-3/ How should I apply the gradient to achieve this? ( I have to apply this to large quantity of images ).

我的结果:

这是我的代码:

func imageWithGradient(img:UIImage!) -> UIImage{

    UIGraphicsBeginImageContext(img.size)
    var context = UIGraphicsGetCurrentContext()

    img.drawAtPoint(CGPointMake(0, 0))

    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let locations:[CGFloat] = [0.50, 1.0]
    //1 = opaque
    //0 = transparent
    let bottom = UIColor(red: 0, green: 0, blue: 0, alpha: 0.5).CGColor
    let top = UIColor(red: 0, green: 0, blue: 0, alpha: 0).CGColor

    let gradient = CGGradientCreateWithColors(colorSpace,
        [top, bottom], locations)


    let startPoint = CGPointMake(img.size.width/2, 0)
    let endPoint = CGPointMake(img.size.width/2, img.size.height)

    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0)

    let image = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return image
}


解决方案

SWIFT 3

func imageWithGradient(img:UIImage!) -> UIImage {

    UIGraphicsBeginImageContext(img.size)
    let context = UIGraphicsGetCurrentContext()

    img.draw(at: CGPoint(x: 0, y: 0))

    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let locations:[CGFloat] = [0.0, 1.0]

    let bottom = UIColor(red: 0, green: 0, blue: 0, alpha: 0.5).cgColor
    let top = UIColor(red: 0, green: 0, blue: 0, alpha: 0).cgColor

    let colors = [top, bottom] as CFArray

    let gradient = CGGradient(colorsSpace: colorSpace, colors: colors, locations: locations)

    let startPoint = CGPoint(x: img.size.width/2, y: 0)
    let endPoint = CGPoint(x: img.size.width/2, y: img.size.height)

    context!.drawLinearGradient(gradient!, start: startPoint, end: endPoint, options: CGGradientDrawingOptions(rawValue: UInt32(0)))

    let image = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return image!
}

这篇关于平滑地应用渐变到UIImage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IT屋!

查看全文
登录 关闭
扫码关注1秒登录
发送“验证码”获取 | 15天全站免登陆