How to save PNG file from NSImage (retina issues)

Question

I\'m doing some operations on images and after I\'m done, I want to save the image as PNG on disk. I\'m doing the following:

+ (void)saveImage:(NSImage *)ima         


        

Answer 1

My 2 cents for OS X including write that handles extensions + offscreen image drawing (method 2); one can verify with NSGraphicsContext.currentContextDrawingToScreen()

func createCGImage() -> CGImage? {

    //method 1
    let image = NSImage(size: NSSize(width: bounds.width, height: bounds.height), flipped: true, drawingHandler: { rect in
        self.drawRect(self.bounds)
        return true
    })
    var rect = CGRectMake(0, 0, bounds.size.width, bounds.size.height)
    return image.CGImageForProposedRect(&rect, context: bitmapContext(), hints: nil)


    //method 2
    if let pdfRep = NSPDFImageRep(data: dataWithPDFInsideRect(bounds)) {
        return pdfRep.CGImageForProposedRect(&rect, context: bitmapContext(), hints: nil)
    }
    return nil
}

func PDFImageData(filter: QuartzFilter?) -> NSData? {
    return dataWithPDFInsideRect(bounds)
}

func bitmapContext() -> NSGraphicsContext? {
    var context : NSGraphicsContext? = nil
    if let imageRep =  NSBitmapImageRep(bitmapDataPlanes: nil,
                                        pixelsWide: Int(bounds.size.width),
                                        pixelsHigh: Int(bounds.size.height), bitsPerSample: 8,
                                        samplesPerPixel: 4, hasAlpha: true, isPlanar: false,
                                        colorSpaceName: NSCalibratedRGBColorSpace,
                                        bytesPerRow: Int(bounds.size.width) * 4,
                                        bitsPerPixel: 32) {
        imageRep.size = NSSize(width: bounds.size.width, height: bounds.size.height)
        context = NSGraphicsContext(bitmapImageRep: imageRep)
    }
    return context
}

func writeImageData(view: MyView, destination: NSURL) {
    if let dest = CGImageDestinationCreateWithURL(destination, imageUTType, 1, nil) {
        let properties  = imageProperties
        let image = view.createCGImage()!
        let queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
        dispatch_async(queue) {
            CGImageDestinationAddImage(dest, image, properties)
            CGImageDestinationFinalize(dest)
        }
    }
}