将UIImage调整为200x200pt / px

82

我一直在努力调整图像的大小。基本上，我很费解：如何缩小UIImage并使其同时变脆 /清晰而不是模糊？

这似乎是一个合法的解决方案，但是以某种方式无法正常工作。

我的应用程序可使用相机胶卷中的照片。这些照片的大小应调整为200x200，而宽度很重要，而不是高度。

不幸的是，我没有示例代码，因为在无法解决问题的愤怒中我将其丢弃。

ios  swift  uiimage 
— swift_dan
source
究竟是什么无法正常工作？您期望得到什么结果，您得到了什么结果？
— ifau 2015年
我希望图像的宽度为200，以这个比率为x的高度。我仍然会像1920x一样获得原始图像。...无论如何
— swift_dan 2015年

Answers:

149

这是我的代码。图片的宽度为850像素，而不是200像素：

 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 imagenow = info[UIImagePickerControllerOriginalImage] as? UIImage

    imageImage.image = resizeImage(imagenow!, newWidth: 200)



    pimg2 = imageImage.image!

    cidnew2 = textFieldCID!.text!
    pname2 = textFieldName!.text
    pmanu2 = textFieldMan!.text
    pnick2 = textFieldNick!.text
    podate2 = textFieldPODate!.text
    pno2 = textFieldArtNo!.text



    self.dismissViewControllerAnimated(true, completion: nil)

}
— swift_dan
source
1
为了摆脱迅速3中的错误，stackoverflow.com
— 37948158/1404324中
3
快速工作4： func resizeImage(image: UIImage, newWidth: CGFloat) -> UIImage { let scale = newWidth / image.size.width let newHeight = image.size.height * scale UIGraphicsBeginImageContext(CGSize(width: newWidth, height: newHeight)) image.draw(in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight)) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage! }
— mikey9 '18
65

基于swift_dan的答案，Swift 3的更新

func resizeImage(image: UIImage, newWidth: CGFloat) -> UIImage? {

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

    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage
}
— 克里斯多夫·R
source
2
如果要在视网膜显示器中保存质量并保存透明图像，请使用：UIGraphicsBeginImageContextWithOptions（CGSize（width：newWidth，height：newHeight），false，0）
— Evgeny Karev
这将我的图像从18MB减少到<1 MB！我在iPad 9.7“上使用了：resizeImage（image：（info：（info [UIImagePickerControllerOriginalImage] as？UIImage）!, newWidth：200）。）。图像取自imagePickerController。使用swift 3.0
— Brian
43

如果要处理包含透明胶片的PNG图像，则可接受的答案功能实际上会将透明区域转换为黑色。

如果您希望缩放并保持透明胶片在适当的位置，请尝试以下功能：

SWIFT 4

extension UIImage {
    func scaleImage(toSize newSize: CGSize) -> UIImage? {
        var newImage: UIImage?
        let newRect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height).integral
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
        if let context = UIGraphicsGetCurrentContext(), let cgImage = self.cgImage {
            context.interpolationQuality = .high
            let flipVertical = CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: 0, ty: newSize.height)
            context.concatenate(flipVertical)
            context.draw(cgImage, in: newRect)
            if let img = context.makeImage() {
                newImage = UIImage(cgImage: img)
            }
            UIGraphicsEndImageContext()
        }
        return newImage
    }
}
— 特拉维斯M.
source
1
惊人的..内存占用从200mb以下减少到18：D
— Tom
3
您还应该考虑将屏幕图像比例替换为UIImage init：let scale = UIScreen.main.scale let newImage = UIImage(cgImage: context.makeImage()!, scale: scale, orientation: .up)
— picciano
1
％30的用户在此函数上崩溃..在context.draw（self.cgImage !, in：newRect）行...崩溃：com.apple.root.utility-qos 0x1001500a8专门的UIImage.scaleImage（toSize：CGSize）- > UIImage？
— Can Aksoy
1
谢谢@CanAksoy，我删除了强制的可选内容，这应该有所帮助。
— 特拉维斯
21

对于Swift 3.0

只需将此代码段添加为的扩展名即可UIImage。但是，请记住，这不会使图像成为正方形，但如果是这种形式，则结果将是正方形。

extension UIImage {
    func resizeImage(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!
    } }
— 法鲁克
source
尝试过此代码。它的确会产生较小的图像；但会留下大量的内存打印内容-在堆上分配一些额外的100-200MB（（
— rommex
10

Swift 4.0-

如果要处理包含透明胶片的图像，则可接受的答案功能实际上会将透明区域转换为黑色。

如果您希望缩放并保持透明胶片在适当的位置，请尝试以下功能：

func resizeImageWith(image: UIImage, newSize: CGSize) -> UIImage {

    let horizontalRatio = newSize.width / image.size.width
    let verticalRatio = newSize.height / image.size.height

    let ratio = max(horizontalRatio, verticalRatio)
    let newSize = CGSize(width: image.size.width * ratio, height: image.size.height * ratio)
    var newImage: UIImage

    if #available(iOS 10.0, *) {
        let renderFormat = UIGraphicsImageRendererFormat.default()
        renderFormat.opaque = false
        let renderer = UIGraphicsImageRenderer(size: CGSize(width: newSize.width, height: newSize.height), format: renderFormat)
        newImage = renderer.image {
            (context) in
            image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
        }
    } else {
        UIGraphicsBeginImageContextWithOptions(CGSize(width: newSize.width, height: newSize.height), isOpaque, 0)
        image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
        newImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
    }

    return newImage
}
— 阿比曼尤·金达尔
source
8

这段代码使用了iOS 10中引入的UIGraphicsImageRenderer：在我的测试中，它比使用UIGraphicsBeginImageContext（Swift 4 / Xcode 9）的早期示例要快10-40％：

extension UIImage {
        func renderResizedImage (newWidth: CGFloat) -> UIImage {
            let scale = newWidth / self.size.width
            let newHeight = self.size.height * scale
            let newSize = CGSize(width: newWidth, height: newHeight)

            let renderer = UIGraphicsImageRenderer(size: newSize)

            let image = renderer.image { (context) in
                self.draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: newSize))
            }
            return image
        }
    }
— 隆美
source
已经有一个关于此的答案：stackoverflow.com/a/45936836/1489885
— HAS
1
@HAS我的代码更短，通过扩展完成，并具有我的性能数据。
— rommex
尽管我真的很喜欢这个答案（使用现代工具，快速简洁的编码），但我必须指出我在使用它时遇到的意外行为。如果原始的UIImage是从相机中裁剪出来的，并且具有一定的尺寸（例如1180x850），并且我要求代码将其“缩小”为newWidth：800，则实际上是将图像尺寸放大了-因为我的设备是3倍视网膜！ ！一个必须提供具有所需比例的UIGraphicsImageRendererFormat ！！！谨防。我们获得了巨大的形象，而不是较小的形象。
— Motti Shneor '19
7

此函数将返回指定宽度的图像：

func scaleImage(image: UIImage, maximumWidth: CGFloat) -> UIImage {
    let rect: CGRect = CGRectMake(0, 0, image.size.width, image.size.height)
    let cgImage: CGImageRef = CGImageCreateWithImageInRect(image.CGImage!, rect)!
    return UIImage(CGImage: cgImage, scale: image.size.width / maximumWidth, orientation: image.imageOrientation)
}

斯威夫特3.0

func scaledImage(_ image: UIImage, maximumWidth: CGFloat) -> UIImage {
    let rect: CGRect = CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height)
    let cgImage: CGImage = image.cgImage!.cropping(to: rect)!
    return UIImage(cgImage: cgImage, scale: image.size.width / maximumWidth, orientation: image.imageOrientation)
}
— 拉希德
source
4

在Swift 4.2中使用最大大小进一步改善@rommex的答案：

private extension UIImage {
    func scaled(to maxSize: CGFloat) -> UIImage? {
        let aspectRatio: CGFloat = min(maxSize / size.width, maxSize / size.height)
        let newSize = CGSize(width: size.width * aspectRatio, height: size.height * aspectRatio)
        let renderer = UIGraphicsImageRenderer(size: newSize)
        return renderer.image { context in
            draw(in: CGRect(origin: CGPoint(x: 0, y: 0), size: newSize))
        }
    }
}
— 巴拉兹·温兹（BalázsVincze）
source
3

此代码在正方形图像上效果很好，不会丢失质量

extension UIImage {

func resize(targetSize: CGSize) -> UIImage {
    return UIGraphicsImageRenderer(size:targetSize).image { _ in
        self.draw(in: CGRect(origin: .zero, size: targetSize))
    }
}

}

答案来自：在 不损失质量的情况下调整图像大小

— 尼娜哈迪
source
2

如果您正在使用kingfisher lib在您的项目中加载图像，并且想要在此处调整大小，则可以采用以下方法：

  • Xcode 8
  • 迅捷3x

    let imageUrl = URL(string: "your image url")
 //Size refer to the size which you want to resize your original image
 let size = CGSize(width: 60, height: 60)
 let processImage = ResizingImageProcessor(targetSize: size, contentMode: .aspectFit)
 cell.courseTitleImage.kf.setImage(with: imageUrl! , placeholder: UIImage(named: "placeholder"), options: [.transition(ImageTransition.fade(1)), .processor(processImage)], progressBlock: nil, completionHandler: nil)

    要么

    调整本地图像的大小：-您可以参考@Christoph R的答案

    • — 阿卜杜勒·卡里姆（Abdul Karim）
    source
    1 
    func getScaledDimension(width: CGFloat, height: CGFloat,new_width: CGFloat, new_height: CGFloat)->CGPoint {

        let widthAspect =  (width / new_width)
        let heightAspect = (height / new_height)
        if widthAspect == 0 || heightAspect == 0 {
            return CGPoint(x: width, y: height)
        }
        var width1 : CGFloat = 0
        var height1 : CGFloat =  0
        if widthAspect > heightAspect {
            width1 = (width) / heightAspect
            height1 = (height) / heightAspect
        } else {
            width1 = (width) / widthAspect
            height1 = (height) / widthAspect
        }

        return CGPoint(x: width1, y: height1 )
    }



    func ResizeImage(image: UIImage, targetSize: CGSize) -> UIImage {

        let rect = CGRectMake(0, 0, targetSize.width, targetSize.height)

        UIGraphicsBeginImageContextWithOptions(targetSize, false, 1.0)
        image.drawInRect(rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }


 let imagesize =  getScaledDimension(image.size.width, height: image.size.height , new_width: Width, new_height: Hieght)

        print("Image Size Scaled Dimension -> H:\(imagesize.x) W:\(imagesize.y)")

        let newImage = ResizeImage(image, targetSize: CGSizeMake(imagesize.x,imagesize.y))
        print("Resize Image Size -> H\(newImage.size.height) W\(newImage.size.width) ")
    — 穆罕默德·拉齐普（Mohammad Razipour）
    source
    1

    这是@Christoph R针对Swift 3.0发布的答案的延续。该代码适用于Swift 5.0.1。

    static func resizeImage(image: UIImage, newWidth: CGFloat) -> UIImage {

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

    return newImage!
}

    在呼叫者站点 

    TaskUtilties.resizeImage(image: rawImage!, newWidth: CGFloat(50))
    — 维卡斯·库马尔
    source
    0

    将图片大小减少1024，您始终可以根据服务器容量进行转换 

    func resizeImage(image: UIImage) -> UIImage {

        if image.size.height >= 1024 && image.size.width >= 1024 {

            UIGraphicsBeginImageContext(CGSize(width:1024, height:1024))
            image.draw(in: CGRect(x:0, y:0, width:1024, height:1024))

            let newImage = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()

            return newImage!

        }
        else if image.size.height >= 1024 && image.size.width < 1024
        {

            UIGraphicsBeginImageContext(CGSize(width:image.size.width, height:1024))
            image.draw(in: CGRect(x:0, y:0, width:image.size.width, height:1024))

            let newImage = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()

            return newImage!

        }
        else if image.size.width >= 1024 && image.size.height < 1024
        {

            UIGraphicsBeginImageContext(CGSize(width:1024, height:image.size.height))
            image.draw(in: CGRect(x:0, y:0, width:1024, height:image.size.height))

            let newImage = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()

            return newImage!

        }
        else
        {
            return image
        }

    }
    — 使莫迪
    source
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