该方法在swift3以后会报大量的错，博主会在近期针对swift3.0进行更正
在swift3.0中，可以下载下来后再用，方法有多种，殊途同归，都是要先下载的，这里提供两种：
方法1:var urlStr = NSURL(string: "/mw690/51f76ed7jw1e3ohzmmnffj.jpg")!var request = NSURLRequest(url: urlStr as URL)var imgData = try! NSURLConnection.sendSynchronousRequest(request as URLRequest, returning: nil)var img: UIImage? = nilvar imageView1 = UIImageView()if imgData != nil {img = UIImage(data: imgData)!imageView1.image = imgprint("width:" + "\(img?.size.width)" + "height:" + "\(img?.size.height)")}方法2:let lhhImageView = UIImageView()lhhImageView.sd_setImage(with: URL(string: "/mw690/51f76ed7jw1e3ohzmmnffj.jpg")) { (image, error, cacheType, imageURL) inprint("width:" + "\(image?.size.width)" + "height:" + "\(image?.size.height)")}self.view.addSubview(lhhImageView)
看代码：
func getImageSize(imageURL:String) ->CGSize {var URL:NSURL?if imageURL.isKindOfClass(NSString) {URL = NSURL(string: imageURL)}if URL == nil{return CGSizeZero // url不正确}let request = NSMutableURLRequest(URL: URL!)let pathExtendsion = URL?.pathExtension?.lowercaseStringvar size = CGSizeZeroif pathExtendsion == "png" {size = self.getPNGImageSize(request)}else if pathExtendsion == "gif"{size = self.getGIFImageSize(request)}else{size = self.getJPGImageSize(request)}if CGSizeEqualToSize(CGSizeZero, size) // 如果获取文件头信息失败,发送异步请求请求原图{guard let data = try? NSURLConnection.sendSynchronousRequest(request, returningResponse: nil) else{return size}let image = UIImage(data: data)if image != nil {size = (image?.size)!}}return size}func getPNGImageSize(request:NSMutableURLRequest) -> CGSize {// 获取PNG图片的大小request.setValue("bytes=16-23", forHTTPHeaderField: "Range")guard let data = try? NSURLConnection.sendSynchronousRequest(request, returningResponse: nil) else{return CGSizeZero}if data.length == 8 {var w1:Int = 0var w2:Int = 0var w3:Int = 0var w4:Int = 0data.getBytes(&w1, range: NSMakeRange(0, 1))data.getBytes(&w2, range: NSMakeRange(1, 1))data.getBytes(&w3, range: NSMakeRange(2, 1))data.getBytes(&w4, range: NSMakeRange(3, 1))let w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4var h1:Int = 0var h2:Int = 0var h3:Int = 0var h4:Int = 0data.getBytes(&h1, range: NSMakeRange(4, 1))data.getBytes(&h2, range: NSMakeRange(5, 1))data.getBytes(&h3, range: NSMakeRange(6, 1))data.getBytes(&h4, range: NSMakeRange(7, 1))let h = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4return CGSizeMake(CGFloat(w), CGFloat(h));}return CGSizeZero;}func getGIFImageSize(request:NSMutableURLRequest) -> CGSize {// 获取GIF图片的大小request.setValue("bytes=6-9", forHTTPHeaderField: "Range")guard var data = try? NSURLConnection.sendSynchronousRequest(request, returningResponse: nil) else{return CGSizeZero}if data.length == 4 {var w1:Int = 0var w2:Int = 0data.getBytes(&w1, range: NSMakeRange(0, 1))data.getBytes(&w2, range: NSMakeRange(1, 1))var w = w1 + (w2 << 8)var h1:Int = 0var h2:Int = 0data.getBytes(&h1, range: NSMakeRange(2, 1))data.getBytes(&h2, range: NSMakeRange(3, 1))var h = h1 + (h2 << 8)return CGSizeMake(CGFloat(w), CGFloat(h));}return CGSizeZero;}func getJPGImageSize(request:NSMutableURLRequest) -> CGSize {// 获取JPG图片的大小request.setValue("bytes=0-209", forHTTPHeaderField: "Range")guard var data = try? NSURLConnection.sendSynchronousRequest(request, returningResponse: nil) else{return CGSizeZero}if data.length <= 0x58 {return CGSizeZero}if data.length < 210 {var w1:Int = 0var w2:Int = 0data.getBytes(&w1, range: NSMakeRange(0x60, 0x1))data.getBytes(&w2, range: NSMakeRange(0x61, 0x1))var w = (w1 << 8) + w2var h1:Int = 0var h2:Int = 0data.getBytes(&h1, range: NSMakeRange(0x5e, 0x1))data.getBytes(&h2, range: NSMakeRange(0x5f, 0x1))var h = (h1 << 8) + h2return CGSizeMake(CGFloat(w), CGFloat(h));}else{var word = 0x0data.getBytes(&word, range: NSMakeRange(0x15, 0x1))if word == 0xdb {data.getBytes(&word, range: NSMakeRange(0x5a, 0x1))if word == 0xdb {var w1:Int = 0var w2:Int = 0data.getBytes(&w1, range: NSMakeRange(0xa5, 0x1))data.getBytes(&w2, range: NSMakeRange(0xa6, 0x1))var w = (w1 << 8) + w2var h1:Int = 0var h2:Int = 0data.getBytes(&h1, range: NSMakeRange(0xa3, 0x1))data.getBytes(&h2, range: NSMakeRange(0xa4, 0x1))var h = (h1 << 8) + h2return CGSizeMake(CGFloat(w), CGFloat(h));}else{var w1:Int = 0var w2:Int = 0data.getBytes(&w1, range: NSMakeRange(0x60, 0x1))data.getBytes(&w2, range: NSMakeRange(0x61, 0x1))var w = (w1 << 8) + w2var h1:Int = 0var h2:Int = 0data.getBytes(&h1, range: NSMakeRange(0x5e, 0x1))data.getBytes(&h2, range: NSMakeRange(0x5f, 0x1))var h = (h1 << 8) + h2return CGSizeMake(CGFloat(w), CGFloat(h));}}else {return CGSizeZero;}}}
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