ImageCompression.swift

func compressImage(image:UIImage) -> NSData? {
    
    var actualHeight : CGFloat = image.size.height
    var actualWidth : CGFloat = image.size.width
    let maxHeight : CGFloat = 1136.0
    let maxWidth : CGFloat = 640.0
    var imgRatio : CGFloat = actualWidth/actualHeight
    let maxRatio : CGFloat = maxWidth/maxHeight
    var compressionQuality : CGFloat = 0.3
    
    if (actualHeight > maxHeight || actualWidth > maxWidth){
        if(imgRatio < maxRatio) {
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight
            actualWidth = imgRatio * actualWidth
            actualHeight = maxHeight
            
        } else if(imgRatio > maxRatio){
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth
            actualHeight = imgRatio * actualHeight
            actualWidth = maxWidth
        } else {
            actualHeight = maxHeight
            actualWidth = maxWidth
            compressionQuality = 1
        }
    }
    
    let rect = CGRect(x: 0, y: 0, width: actualWidth, height: actualHeight)
    UIGraphicsBeginImageContext(rect.size);
    image.drawInRect(rect)
    let img = UIGraphicsGetImageFromCurrentImageContext()
    let imageData = UIImageJPEGRepresentation(img, compressionQuality)
    UIGraphicsEndImageContext()
    
    return imageData
}