问样品NSImage和保持质量(迅速3)

EN

    let bg = NSImage(imageLiteralResourceName: "ref")
    let tex = SKTexture(image: bg)
    let sprite = SKSpriteNode(texture: tex)
    sprite.position = CGPoint(x: size.width/2, y:size.height/2)
    addChild(sprite)

    let sample = bg.sample(size: NSSize(width: 100, height: 100))
    let sampletex = SKTexture(image:sample!)
    let samplesprite = SKSpriteNode(texture:sampletex)
    samplesprite.position = CGPoint(x: 60, y:size.height/2)
    addChild(samplesprite)

extension NSImage {

    /// Returns the height of the current image.
    var height: CGFloat {
        return self.size.height
    }

    /// Returns the width of the current image.
    var width: CGFloat {
        return self.size.width
    }

    func sample(size: NSSize) -> NSImage? {
        // Resize the current image, while preserving the aspect ratio.
        let source = self

        // Make sure that we are within a suitable range
        var checkedSize    = size
        checkedSize.width  = floor(min(checkedSize.width,source.size.width * 0.9))
        checkedSize.height = floor(min(checkedSize.height, source.size.height * 0.9))

        // Get random points for the crop.
        let x = randomNumber(range: 0...(Int(source.width) - Int(checkedSize.width)))
        let y = randomNumber(range: 0...(Int(source.height) - Int(checkedSize.height)))

        // Create the cropping frame.
        var frame = NSRect(x: x, y: y, width: Int(checkedSize.width), height: Int(checkedSize.height))

        // let ref = source.cgImage.cropping(to:frame)
        let ref = source.cgImage(forProposedRect: &frame, context: nil, hints: nil)
        let rep = NSBitmapImageRep(cgImage: ref!)

        // Create a new image with the new size
        let img = NSImage(size: checkedSize)

        // Set a graphics context
        img.lockFocus()
        defer { img.unlockFocus() }

        // Fill in the sample image
        if rep.draw(in: NSMakeRect(0, 0, checkedSize.width, checkedSize.height),
                    from: frame,
                    operation: NSCompositingOperation.copy,
                    fraction: 1.0,
                    respectFlipped: false,
                    hints: [NSImageHintInterpolation:NSImageInterpolation.high.rawValue]) {
            // Return the cropped image.
            return img
        }

        // Return nil in case anything fails.
        return nil
    }

}

func randomNumber(range: ClosedRange<Int> = 0...100) -> Int {
    let min = range.lowerBound
    let max = range.upperBound
    return Int(arc4random_uniform(UInt32(1 + max - min))) + min
}