在swift3缩小图像尺寸较小

我正在尝试将正在graphics编程的图像缩放到照片库中。 我正在试图缩小图像，使其更小。 我将如何使用下面的代码来缩小图像

image1.scale 

Answer 1

使用此扩展名来调整图片大小：

 extension UIImage{ func resizeImageWith(newSize: CGSize) -> UIImage { let horizontalRatio = newSize.width / size.width let verticalRatio = newSize.height / size.height let ratio = max(horizontalRatio, verticalRatio) let newSize = CGSize(width: size.width * ratio, height: size.height * ratio) UIGraphicsBeginImageContextWithOptions(newSize, true, 0) draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: newSize)) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage! } } 

基本上，你正在计算宽高比，以保持图像的完整性，同时调整它的大小。 然后你得到当前的图像上下文，并绘制在指定的矩形，最后返回它作为一个新的形象。

Answer 2

尝试这个：

第一种方法：

 func resizeImage(image: UIImage, newWidth: CGFloat) -> UIImage { let scale = newWidth / image.size.width let newHeight = image.size.height * scale UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight)) image.drawInRect(CGRectMake(0, 0, newWidth, newHeight)) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage } 

第二种方法：

 import UIKit func RBSquareImageTo(image: UIImage, size: CGSize) -> UIImage { return RBResizeImage(RBSquareImage(image), size) } func RBSquareImage(image: UIImage) -> UIImage { var originalWidth = image.size.width var originalHeight = image.size.height var edge: CGFloat if originalWidth > originalHeight { edge = originalHeight } else { edge = originalWidth } var posX = (originalWidth - edge) / 2.0 var posY = (originalHeight - edge) / 2.0 var cropSquare = CGRectMake(posX, posY, edge, edge) var imageRef = CGImageCreateWithImageInRect(image.CGImage, cropSquare); return UIImage(CGImage: imageRef, scale: UIScreen.mainScreen().scale, orientation: image.imageOrientation) } func RBResizeImage(image: UIImage, targetSize: CGSize) -> UIImage { let size = image.size let widthRatio = targetSize.width / image.size.width let heightRatio = targetSize.height / image.size.height // Figure out what our orientation is, and use that to form the rectangle var newSize: CGSize if(widthRatio > heightRatio) { newSize = CGSizeMake(size.width * heightRatio, size.height * heightRatio) } else { newSize = CGSizeMake(size.width * widthRatio, size.height * widthRatio) } // This is the rect that we've calculated out and this is what is actually used below let rect = CGRectMake(0, 0, newSize.width, newSize.height) // Actually do the resizing to the rect using the ImageContext stuff UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0) image.drawInRect(rect) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage } 

参考：

1. 这里

2. 这里

Answer 3

这可能是有帮助的，这种方法将做比例resize的图像质量好。

 func resizeImage(image: UIImage, withSize: CGSize) -> UIImage { var actualHeight: CGFloat = image.size.height var actualWidth: CGFloat = image.size.width let maxHeight: CGFloat = withSize.width let maxWidth: CGFloat = withSize.height var imgRatio: CGFloat = actualWidth/actualHeight let maxRatio: CGFloat = maxWidth/maxHeight let compressionQuality = 0.5//50 percent compression 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 } } let rect: CGRect = CGRect(x: 0.0, y: 0.0, width: actualWidth, height: actualHeight) UIGraphicsBeginImageContext(rect.size) image.draw(in: rect) let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()! let imageData = UIImageJPEGRepresentation(image, CGFloat(compressionQuality)) UIGraphicsEndImageContext() let resizedImage = UIImage(data: imageData!) return resizedImage! } 

像这样调用这个方法，

 resizeImage(image: UIImage(named: "ImageName"), withSize: CGSize(width: 300, height: 300)) 

谢谢：）

Answer 4

  func resizeImage(image: UIImage, newWidth: CGFloat) -> UIImage { let scale = newWidth / image.size.width let newHeight = image.size.height * scale UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight)) image.drawInRect(CGRectMake(0, 0, newWidth, newHeight)) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage } @IBAction func chooseImage(sender: AnyObject) { var myPickerController = UIImagePickerController() myPickerController.sourceType = UIImagePickerControllerSourceType.PhotoLibrary myPickerController.delegate = self; self.presentViewController(myPickerController, animated: true, completion: nil) } func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [NSObject : AnyObject]) { var image = info[UIImagePickerControllerOriginalImage] as? UIImage let scaledImage:UIImage = resizeImage(image!, newWidth: 200) self.dismissViewControllerAnimated(true, completion: nil) }