在swift3中将图像缩放到更小的尺寸[关闭]

Question

我正在尝试缩放正在以图形方式编程到照片库中的图像。我正在尝试缩放图像以使其更小。我将如何使用下面的代码使图像更小

   image1.scale

Answer 1

使用这个扩展来调整你的图片大小：

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，您正在计算纵横比以在调整图像大小时保持图像完整。然后，您将获取当前图像上下文并将其绘制在指定的矩形中，最后将其作为新图像返回。

Answer 2

试试这个：

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. Here

2. Here

Answer 3

这可能会有所帮助，此方法可以按比例调整质量良好的图像。

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)

}

Swift 4 版本

extension UIImage {

    func resize(withWidth newWidth: CGFloat) -> UIImage? {

        let scale = newWidth / self.size.width
        let newHeight = self.size.height * scale
        UIGraphicsBeginImageContext(CGSize(width: newWidth, height: newHeight))
        self.draw(in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }
}