调整图像大小但保留硬边

Question

我正在使用 link - Resize UIImage by keeping Aspect ratio and width 中的一段代码，它运行良好，但我想知道是否可以更改它以保留像素的硬边。我想将图像的大小加倍并保留像素的硬边。

class func resizeImage(image: UIImage, newHeight: CGFloat) -> UIImage {

    let scale = newHeight / image.size.height
    let newWidth = image.size.width * scale
    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight))
    image.drawInRect(CGRectMake(0, 0, newWidth, newHeight))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage
}

What I want it to do

What it does

在Photoshop中调整大小时有最近邻插值，在iOS中有类似的东西吗？

Answer 1

进一步挖掘并找到了答案 -

但是

CGContextSetInterpolationQuality(context, kCGInterpolationHigh)

改为写

CGContextSetInterpolationQuality(context, CGInterpolationQuality.None)

Answer 2

您需要使用 CISamplerclass（仅在 iOS 9 中可用）并且我认为需要为其创建您自己的自定义图像处理过滤器

您可以找到更多信息here and here too

Answer 3

受已接受答案的启发，更新为Swift 5.

Swift 5

let image = UIImage(named: "Foo")!
let scale: CGFloat = 2.0

let newSize = image.size.applying(CGAffineTransform(scaleX: scale, y: scale))
UIGraphicsBeginImageContextWithOptions(newSize, false, UIScreen.main.scale)
let context = UIGraphicsGetCurrentContext()!
context.interpolationQuality = .none
let newRect = CGRect(origin: .zero, size: newSize)
image.draw(in: newRect)

let newImage = UIImage(cgImage: context.makeImage()!)
UIGraphicsEndImageContext()

调整图像大小但保留硬边

Resizing an image but preserving hard edges

xcode

image

image-resizing

ios

swift