silica-viewer/SilicaViewer/Extensions.swift

import Foundation
import AppKit

extension CGImage {
    func toGrayscale() -> CGImage? {
        let rect = CGRect(x: 0, y: 0, width: width, height: height)
        let grayColorSpace = CGColorSpaceCreateDeviceGray()
        let maskBitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue).union(.byteOrder16Big)
        
        let ccgContext = CGContext(data: nil, width: width, height: height, bitsPerComponent: 16, bytesPerRow: width * 2, space: grayColorSpace, bitmapInfo: maskBitmapInfo.rawValue)
        
        ccgContext?.setFillColor(.black)
        ccgContext?.fill(rect)
        
        ccgContext?.draw(self, in: rect)
                
        return ccgContext?.makeImage()
    }

    // we really only handle 90 degree turns, which is totally fine
    func rotate(angle : CGFloat, flipHorizontally : Bool, flipVertically : Bool) -> CGImage? {
        let newWidth: CGFloat = CGFloat(height)
        let newHeight: CGFloat = CGFloat(width)
        
        let ctx = CGContext(data: nil,
                            width: Int(newWidth),
                            height: Int(newHeight),
                            bitsPerComponent: bitsPerComponent,
                            bytesPerRow: bytesPerRow,
                            space: colorSpace!,
                            bitmapInfo: bitmapInfo.rawValue)!
        
        ctx.translateBy(x: newWidth / 2, y: newHeight / 2)
        ctx.rotate(by: -angle)
        
        if flipVertically {
            ctx.scaleBy(x: 1.0, y: -1.0)
        }
        
        if flipHorizontally {
            ctx.scaleBy(x: -1.0, y: 1.0)
        }
 
        let dstRect = CGRect(x: -width / 2, y: -height / 2, width: width, height: height)
        ctx.draw(self, in: dstRect)
        
        return ctx.makeImage()
    }
}

extension NSImage {
    func imageRotatedByDegreess(degrees:CGFloat) -> NSImage {
        var imageBounds = NSMakeRect(0.0, 0.0, size.width, size.height)
        
        let pathBounds = NSBezierPath(rect: imageBounds)
        var transform = NSAffineTransform()
        transform.rotate(byDegrees: degrees)
        pathBounds.transform(using: transform as AffineTransform)
        
        let rotatedBounds:NSRect = NSMakeRect(NSZeroPoint.x, NSZeroPoint.y, pathBounds.bounds.size.width, pathBounds.bounds.size.height )
        let rotatedImage = NSImage(size: rotatedBounds.size)
        
        imageBounds.origin.x = NSMidX(rotatedBounds) - (NSWidth(imageBounds) / 2)
        imageBounds.origin.y  = NSMidY(rotatedBounds) - (NSHeight(imageBounds) / 2)
        
        transform = NSAffineTransform()
        transform.translateX(by: +(NSWidth(rotatedBounds) / 2 ), yBy: +(NSHeight(rotatedBounds) / 2))
        transform.rotate(byDegrees: degrees)
        transform.translateX(by: -(NSWidth(rotatedBounds) / 2 ), yBy: -(NSHeight(rotatedBounds) / 2))
        
        rotatedImage.lockFocus()
        transform.concat()
        
        self.draw(in: imageBounds, from: .zero, operation: .copy, fraction: 1.0)
        
        rotatedImage.unlockFocus()
        
        return rotatedImage
    }
    
    func flipHorizontally() -> NSImage {
        let flipedImage = NSImage(size: size)
        flipedImage.lockFocus()
        
        let transform = NSAffineTransform()
        transform.translateX(by: size.width, yBy: 0.0)
        transform.scaleX(by: -1.0, yBy: 1.0)
        transform.concat()
        
        let rect = NSMakeRect(0, 0, size.width, size.height)
        self.draw(at: .zero, from: rect, operation: .sourceOver, fraction: 1.0)
        
        flipedImage.unlockFocus()
        
        return flipedImage
    }
    
    func flipVertically() -> NSImage {
        let flipedImage = NSImage(size: size)
        flipedImage.lockFocus()
        
        let transform = NSAffineTransform()
        transform.translateX(by: 0.0, yBy: size.height)
        transform.scaleX(by: 1.0, yBy: -1.0)
        transform.concat()
        
        let rect = NSMakeRect(0, 0, size.width, size.height)
        self.draw(at: .zero, from: rect, operation: .sourceOver, fraction: 1.0)
        
        flipedImage.unlockFocus()
        
        return flipedImage
    }
}

extension NSView {
    class func fromNib<T: NSView>() -> T? {
        var topLevelObjects : NSArray?
        guard Bundle.main.loadNibNamed("\(self)", owner: nil, topLevelObjects: &topLevelObjects) else {
            return nil
        }
        return topLevelObjects!.first(where: { $0 is T }) as? T
    }
}