直接渲染CGImage（而不是UIImage）？ [英] Render a CGImage (rather than UIImage) directly?

问题描述

我正在制作 CGImage

func otf() -> CGImage {

是渐变上的贝塞尔曲线蒙版。因此，

which is a bezier mask on a gradient. So,

    // the path
    let p = UIBezierPath()
    p.moveTo etc

    // the mask
    let m = CAShapeLayer()
    set size etc
    m.path = p.cgPath

    // the layer
    let l = CAGradientLayer()
    set colors etc
    l.mask = m

完成。因此，以通常的方式渲染 UIImage ...

it's done. So then render a UIImage in the usual way ...

    UIGraphicsBeginImageContextWithOptions(sz.size, false, UIScreen.main.scale)
    l.render(in: UIGraphicsGetCurrentContext()!)
    let r = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()

但是。然后要返回它，当然必须转换为CGImage

But. Then to return it, of course you have to convert to a CGImage

    return r.cgImage!

（如果您使用..

UIGraphicsImageRenderer(bounds: b).image { (c) in v.layer.render(in: c) }

..您得到的是UIImage，而不是CGImage。）

.. you get a UIImage, not a CGImage.)

似乎应该有更好的选择/更优雅的方式-是否有某种方法可以更直接地 构建CGImage ，而不是构建UIImage，然后转换？

Seems like there should be a better / more elegant way - is there some way to more directly "build a CGImage", rather than "building a UIImage, and then converting"?

推荐答案

您需要创建CGContext才能生成直接CGImage

You need to create CGContext to generate direct CGImage

注意：- 使用此代码创建直接CGImage

func createImage() -> CGImage? {
        // the path
        var p = UIBezierPath()
        p = UIBezierPath(arcCenter: CGPoint(x: 100,y: 100), radius: CGFloat(200), startAngle: CGFloat(0), endAngle:CGFloat(Double.pi * 2), clockwise: true)


        // the mask
        let m = CAShapeLayer()
        m.path = p.cgPath

        // the layer
        let layer = CAGradientLayer()
        layer.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
        layer.colors = [UIColor.red.cgColor, UIColor.black.cgColor]
        layer.mask = m



        let imageSize = CGSize(width: 200, height: 200)

        let colorSpace = CGColorSpace(name: CGColorSpace.sRGB)!
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
        guard let context = CGContext(data: nil, width: Int(imageSize.width), height: Int(imageSize.height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue) else { return nil }

        layer.render(in: context)
        let img = context.makeImage()
        return img
    }

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