accessing UIImage properties without loading in memory the image

Question

As you know the iphone guidelines discourage loading uiimages that are greater than 1024x1024.

The size of the images that i would have to load varies, and i would l

Answer 1

Swift 3 version of the answer:

import Foundation
import ImageIO

func sizeForImage(at url: URL) -> CGSize? {

    guard let imageSource = CGImageSourceCreateWithURL(url as CFURL, nil)
        , let imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil) as? [AnyHashable: Any]
        , let pixelWidth = imageProperties[kCGImagePropertyPixelWidth as String]
        , let pixelHeight = imageProperties[kCGImagePropertyPixelHeight as String]
        , let orientationNumber = imageProperties[kCGImagePropertyOrientation as String]
        else {
            return nil
    }

    var width: CGFloat = 0, height: CGFloat = 0, orientation: Int = 0

    CFNumberGetValue(pixelWidth as! CFNumber, .cgFloatType, &width)
    CFNumberGetValue(pixelHeight as! CFNumber, .cgFloatType, &height)
    CFNumberGetValue(orientationNumber as! CFNumber, .intType, &orientation)

    // Check orientation and flip size if required
    if orientation > 4 { let temp = width; width = height; height = temp }

    return CGSize(width: width, height: height)
}