Swift'de görüntü nasıl yeniden boyutlandırılır?

Swift ve Parse.com'u kullanarak iOS için bir uygulama yapıyorum

Kullanıcının bir resim seçiciden bir resim seçmesine ve ardından arka ucuma yüklemeden önce seçilen resmi 200x200 piksel olarak yeniden boyutlandırmasına izin vermeye çalışıyorum.

Parse.com'da, görüntüleri yeniden boyutlandırmak için bu kodu veren "AnyPic" adlı bir Instagram kopyalama uygulaması için bir öğretici var, ancak bu, Objective-C'de ...

// Resize the image to be square (what is shown in the preview)
UIImage *resizedImage = [anImage resizedImageWithContentMode:UIViewContentModeScaleAspectFit
        bounds:CGSizeMake(560.0f, 560.0f)
        interpolationQuality:kCGInterpolationHigh];
// Create a thumbnail and add a corner radius for use in table views
UIImage *thumbnailImage = [anImage thumbnailImage:86.0f
        transparentBorder:0.0f
        cornerRadius:10.0f
        interpolationQuality:kCGInterpolationDefault];

Swift'de seçilen resmin 200x200 piksellik bir versiyonunu (daha sonra yüklemek için) nasıl oluşturabilirim?

Ve thumbnailImage işlevi ne yapıyor?

Daha fazla ayrıntı için blog gönderime, hızlı bir şekilde resmi yeniden boyutlandır ve C hedefine bakın.

Aşağıdaki gibi hızlı bir şekilde görüntü yeniden boyutlandırma işlevi.

func resizeImage(image: UIImage, targetSize: CGSize) -> UIImage {
    let size = image.size

    let widthRatio  = targetSize.width  / size.width
    let heightRatio = targetSize.height / 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
}

Yukarıdaki işlevi kullanın ve görüntüyü aşağıdaki kod gibi 200 * 200 ile yeniden boyutlandırın

self.resizeImage(UIImage(named: "yourImageName")!, targetSize: CGSizeMake(200.0, 200.0))

swift3 güncellendi

 func resizeImage(image: UIImage, targetSize: CGSize) -> UIImage {
    let size = image.size

    let widthRatio  = targetSize.width  / size.width
    let heightRatio = targetSize.height / size.height

    // Figure out what our orientation is, and use that to form the rectangle
    var newSize: CGSize
    if(widthRatio > heightRatio) {
        newSize = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
    } else {
        newSize = CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
    }

    // This is the rect that we've calculated out and this is what is actually used below
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

    // Actually do the resizing to the rect using the ImageContext stuff
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
}

Swift 4.0 ve iOS 10 için

    extension UIImage {
        func resizeImage(_ dimension: CGFloat, opaque: Bool, contentMode: UIViewContentMode = .scaleAspectFit) -> UIImage {
            var width: CGFloat
            var height: CGFloat
            var newImage: UIImage

            let size = self.size
            let aspectRatio =  size.width/size.height

            switch contentMode {
                case .scaleAspectFit:
                    if aspectRatio > 1 {                            // Landscape image
                        width = dimension
                        height = dimension / aspectRatio
                    } else {                                        // Portrait image
                        height = dimension
                        width = dimension * aspectRatio
                    }

            default:
                fatalError("UIIMage.resizeToFit(): FATAL: Unimplemented ContentMode")
            }

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

            return newImage
        }
    }

@KiritModi'nin yanıtı 2015 yılına ait olduğundan, bu Swift 3.0'ın sürümü:

func resizeImage(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 = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
    } else {
        newSize = CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
    }

    // This is the rect that we've calculated out and this is what is actually used below
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

    // Actually do the resizing to the rect using the ImageContext stuff
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
}

Swift 4 için UIImage'da kendine referansla bir uzantı yapardım.

import UIKit
extension UIImage {
  func resizeImage(targetSize: CGSize) -> UIImage {
    let size = self.size
    let widthRatio  = targetSize.width  / size.width
    let heightRatio = targetSize.height / size.height
    let newSize = widthRatio > heightRatio ?  CGSize(width: size.width * heightRatio, height: size.height * heightRatio) : CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    self.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
  }
}

Detaylar

• Xcode 10.2.1 (10E1001), Swift 5

Bağlantılar

• https://gist.github.com/eugenebokhan/5e62a0155754ae6aa6c3c13cf1744930
• Görüntü Boyutlandırma Teknikleri

Çözüm

import UIKit
import CoreGraphics
import Accelerate

extension UIImage {

    public enum ResizeFramework {
        case uikit, coreImage, coreGraphics, imageIO, accelerate
    }

    /// Resize image with ScaleAspectFit mode and given size.
    ///
    /// - Parameter dimension: width or length of the image output.
    /// - Parameter resizeFramework: Technique for image resizing: UIKit / CoreImage / CoreGraphics / ImageIO / Accelerate.
    /// - Returns: Resized image.

    func resizeWithScaleAspectFitMode(to dimension: CGFloat, resizeFramework: ResizeFramework = .coreGraphics) -> UIImage? {

        if max(size.width, size.height) <= dimension { return self }

        var newSize: CGSize!
        let aspectRatio = size.width/size.height

        if aspectRatio > 1 {
            // Landscape image
            newSize = CGSize(width: dimension, height: dimension / aspectRatio)
        } else {
            // Portrait image
            newSize = CGSize(width: dimension * aspectRatio, height: dimension)
        }

        return resize(to: newSize, with: resizeFramework)
    }

    /// Resize image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Parameter resizeFramework: Technique for image resizing: UIKit / CoreImage / CoreGraphics / ImageIO / Accelerate.
    /// - Returns: Resized image.
    public func resize(to newSize: CGSize, with resizeFramework: ResizeFramework = .coreGraphics) -> UIImage? {
        switch resizeFramework {
            case .uikit: return resizeWithUIKit(to: newSize)
            case .coreGraphics: return resizeWithCoreGraphics(to: newSize)
            case .coreImage: return resizeWithCoreImage(to: newSize)
            case .imageIO: return resizeWithImageIO(to: newSize)
            case .accelerate: return resizeWithAccelerate(to: newSize)
        }
    }

    // MARK: - UIKit

    /// Resize image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Returns: Resized image.
    private func resizeWithUIKit(to newSize: CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(newSize, true, 1.0)
        self.draw(in: CGRect(origin: .zero, size: newSize))
        defer { UIGraphicsEndImageContext() }
        return UIGraphicsGetImageFromCurrentImageContext()
    }

    // MARK: - CoreImage

    /// Resize CI image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Returns: Resized image.
    // https://developer.apple.com/library/archive/documentation/GraphicsImaging/Reference/CoreImageFilterReference/index.html
    private func resizeWithCoreImage(to newSize: CGSize) -> UIImage? {
        guard let cgImage = cgImage, let filter = CIFilter(name: "CILanczosScaleTransform") else { return nil }

        let ciImage = CIImage(cgImage: cgImage)
        let scale = (Double)(newSize.width) / (Double)(ciImage.extent.size.width)

        filter.setValue(ciImage, forKey: kCIInputImageKey)
        filter.setValue(NSNumber(value:scale), forKey: kCIInputScaleKey)
        filter.setValue(1.0, forKey: kCIInputAspectRatioKey)
        guard let outputImage = filter.value(forKey: kCIOutputImageKey) as? CIImage else { return nil }
        let context = CIContext(options: [.useSoftwareRenderer: false])
        guard let resultCGImage = context.createCGImage(outputImage, from: outputImage.extent) else { return nil }
        return UIImage(cgImage: resultCGImage)
    }

    // MARK: - CoreGraphics

    /// Resize image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Returns: Resized image.
    private func resizeWithCoreGraphics(to newSize: CGSize) -> UIImage? {
        guard let cgImage = cgImage, let colorSpace = cgImage.colorSpace else { return nil }

        let width = Int(newSize.width)
        let height = Int(newSize.height)
        let bitsPerComponent = cgImage.bitsPerComponent
        let bytesPerRow = cgImage.bytesPerRow
        let bitmapInfo = cgImage.bitmapInfo

        guard let context = CGContext(data: nil, width: width, height: height,
                                      bitsPerComponent: bitsPerComponent,
                                      bytesPerRow: bytesPerRow, space: colorSpace,
                                      bitmapInfo: bitmapInfo.rawValue) else { return nil }
        context.interpolationQuality = .high
        let rect = CGRect(origin: CGPoint.zero, size: newSize)
        context.draw(cgImage, in: rect)

        return context.makeImage().flatMap { UIImage(cgImage: $0) }
    }

    // MARK: - ImageIO

    /// Resize image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Returns: Resized image.
    private func resizeWithImageIO(to newSize: CGSize) -> UIImage? {
        var resultImage = self

        guard let data = jpegData(compressionQuality: 1.0) else { return resultImage }
        let imageCFData = NSData(data: data) as CFData
        let options = [
            kCGImageSourceCreateThumbnailWithTransform: true,
            kCGImageSourceCreateThumbnailFromImageAlways: true,
            kCGImageSourceThumbnailMaxPixelSize: max(newSize.width, newSize.height)
            ] as CFDictionary
        guard   let source = CGImageSourceCreateWithData(imageCFData, nil),
                let imageReference = CGImageSourceCreateThumbnailAtIndex(source, 0, options) else { return resultImage }
        resultImage = UIImage(cgImage: imageReference)

        return resultImage
    }

    // MARK: - Accelerate

    /// Resize image from given size.
    ///
    /// - Parameter newSize: Size of the image output.
    /// - Returns: Resized image.
    private func resizeWithAccelerate(to newSize: CGSize) -> UIImage? {
        var resultImage = self

        guard let cgImage = cgImage, let colorSpace = cgImage.colorSpace else { return nil }

        // create a source buffer
        var format = vImage_CGImageFormat(bitsPerComponent: numericCast(cgImage.bitsPerComponent),
                                          bitsPerPixel: numericCast(cgImage.bitsPerPixel),
                                          colorSpace: Unmanaged.passUnretained(colorSpace),
                                          bitmapInfo: cgImage.bitmapInfo,
                                          version: 0,
                                          decode: nil,
                                          renderingIntent: .absoluteColorimetric)
        var sourceBuffer = vImage_Buffer()
        defer {
            sourceBuffer.data.deallocate()
        }

        var error = vImageBuffer_InitWithCGImage(&sourceBuffer, &format, nil, cgImage, numericCast(kvImageNoFlags))
        guard error == kvImageNoError else { return resultImage }

        // create a destination buffer
        let destWidth = Int(newSize.width)
        let destHeight = Int(newSize.height)
        let bytesPerPixel = cgImage.bitsPerPixel
        let destBytesPerRow = destWidth * bytesPerPixel
        let destData = UnsafeMutablePointer<UInt8>.allocate(capacity: destHeight * destBytesPerRow)
        defer {
            destData.deallocate()
        }
        var destBuffer = vImage_Buffer(data: destData, height: vImagePixelCount(destHeight), width: vImagePixelCount(destWidth), rowBytes: destBytesPerRow)

        // scale the image
        error = vImageScale_ARGB8888(&sourceBuffer, &destBuffer, nil, numericCast(kvImageHighQualityResampling))
        guard error == kvImageNoError else { return resultImage }

        // create a CGImage from vImage_Buffer
        let destCGImage = vImageCreateCGImageFromBuffer(&destBuffer, &format, nil, nil, numericCast(kvImageNoFlags), &error)?.takeRetainedValue()
        guard error == kvImageNoError else { return resultImage }

        // create a UIImage
        if let scaledImage = destCGImage.flatMap({ UIImage(cgImage: $0) }) {
            resultImage = scaledImage
        }

        return resultImage
    }
}

Kullanım

Görüntü boyutunu al

import UIKit

// https://stackoverflow.com/a/55765409/4488252
extension UIImage {
    func getFileSizeInfo(allowedUnits: ByteCountFormatter.Units = .useMB,
                         countStyle: ByteCountFormatter.CountStyle = .memory,
                         compressionQuality: CGFloat = 1.0) -> String? {
        // https://developer.apple.com/documentation/foundation/bytecountformatter
        let formatter = ByteCountFormatter()
        formatter.allowedUnits = allowedUnits
        formatter.countStyle = countStyle
        return getSizeInfo(formatter: formatter, compressionQuality: compressionQuality)
    }

    func getSizeInfo(formatter: ByteCountFormatter, compressionQuality: CGFloat = 1.0) -> String? {
        guard let imageData = jpegData(compressionQuality: compressionQuality) else { return nil }
        return formatter.string(fromByteCount: Int64(imageData.count))
    }
}

Test işlevi

private func test() {
    guard let img = UIImage(named: "img") else { return }
    printInfo(of: img, title: "original image |")
    let dimension: CGFloat = 2000

    var framework: UIImage.ResizeFramework = .accelerate
    var startTime = Date()
    if let img = img.resizeWithScaleAspectFitMode(to: dimension, resizeFramework: framework) {
        printInfo(of: img, title: "resized image |", with: framework, startedTime: startTime)
    }

    framework = .coreGraphics
    startTime = Date()
    if let img = img.resizeWithScaleAspectFitMode(to: dimension, resizeFramework: framework) {
        printInfo(of: img, title: "resized image |", with: framework, startedTime: startTime)
    }

    framework = .coreImage
    startTime = Date()
    if let img = img.resizeWithScaleAspectFitMode(to: dimension, resizeFramework: framework) {
        printInfo(of: img, title: "resized image |", with: framework, startedTime: startTime)
    }

    framework = .imageIO
    startTime = Date()
    if let img = img.resizeWithScaleAspectFitMode(to: dimension, resizeFramework: framework) {
        printInfo(of: img, title: "resized image |", with: framework, startedTime: startTime)
    }

    framework = .uikit
    startTime = Date()
    if let img = img.resizeWithScaleAspectFitMode(to: dimension, resizeFramework: framework) {
        printInfo(of: img, title: "resized image |", with: framework, startedTime: startTime)
    }
}

private func printInfo(of image: UIImage, title: String, with resizeFramework: UIImage.ResizeFramework? = nil, startedTime: Date? = nil) {
    var description = "\(title) \(image.size)"
    if let startedTime = startedTime { description += ", execution time: \(Date().timeIntervalSince(startedTime))" }
    if let fileSize = image.getFileSizeInfo(compressionQuality: 0.9) { description += ", size: \(fileSize)" }
    if let resizeFramework = resizeFramework { description += ", framework: \(resizeFramework)" }
    print(description)
}

Çıktı

original image | (5790.0, 8687.0), size: 17.1 MB
resized image | (1333.0, 2000.0), execution time: 0.8192930221557617, size: 1.1 MB, framework: accelerate
resized image | (1333.0, 2000.0), execution time: 0.44696998596191406, size: 1 MB, framework: coreGraphics
resized image | (1334.0, 2000.0), execution time: 54.172922015190125, size: 1.1 MB, framework: coreImage
resized image | (1333.0, 2000.0), execution time: 1.8765920400619507, size: 1.1 MB, framework: imageIO
resized image | (1334.0, 2000.0), execution time: 0.4638739824295044, size: 1 MB, framework: uikit

AlamofireImage'ı kullanmak da mümkündür ( https://github.com/Alamofire/AlamofireImage )

let size = CGSize(width: 30.0, height: 30.0)
let aspectScaledToFitImage = image.af_imageAspectScaled(toFit: size)

Önceki gönderideki işlev bana bulanık bir sonuç verdi.

Swift 3 Sürümü ve Uzantı stili

Bu cevap @Kirit Modi'den geliyor.

extension UIImage {

    func resizeImage(targetSize: CGSize) -> UIImage {
        let size = self.size

        let widthRatio  = targetSize.width  / size.width
        let heightRatio = targetSize.height / size.height

        // Figure out what our orientation is, and use that to form the rectangle
        var newSize: CGSize
        if(widthRatio > heightRatio) {
            newSize = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
        } else {
            newSize = CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
        }

        // This is the rect that we've calculated out and this is what is actually used below
        let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

        // Actually do the resizing to the rect using the ImageContext stuff
        UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage!
    }
}

Swift 5.0 ve iOS 12 için

extension UIImage {
    func imageResized(to size: CGSize) -> UIImage {
        return UIGraphicsImageRenderer(size: size).image { _ in
            draw(in: CGRect(origin: .zero, size: size))
        }
    }
}

kullanım:

let image = #imageLiteral(resourceName: "ic_search")
cell!.search.image = image.imageResized(to: cell!.search.frame.size)

Swift 4, uzatma versiyonu, KENARLARDA BEYAZ ÇİZGİ YOK.

image.draw()Tamsayı olmayan değerlerle çağrıldığında, ortaya çıkan görüntünün sağ veya alt kenarda beyaz bir çizgi artefaktı gösterebileceğinden kimse bahsetmiyor gibi görünüyor .

extension UIImage {

    func scaled(with scale: CGFloat) -> UIImage? {
        // size has to be integer, otherwise it could get white lines
        let size = CGSize(width: floor(self.size.width * scale), height: floor(self.size.height * scale))
        UIGraphicsBeginImageContext(size)
        draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }

Swift 4 Sürümü

extension UIImage {
    func resizeImage(_ newSize: CGSize) -> UIImage? {
        func isSameSize(_ newSize: CGSize) -> Bool {
            return size == newSize
        }

        func scaleImage(_ newSize: CGSize) -> UIImage? {
            func getScaledRect(_ newSize: CGSize) -> CGRect {
                let ratio   = max(newSize.width / size.width, newSize.height / size.height)
                let width   = size.width * ratio
                let height  = size.height * ratio
                return CGRect(x: 0, y: 0, width: width, height: height)
            }

            func _scaleImage(_ scaledRect: CGRect) -> UIImage? {
                UIGraphicsBeginImageContextWithOptions(scaledRect.size, false, 0.0);
                draw(in: scaledRect)
                let image = UIGraphicsGetImageFromCurrentImageContext() ?? UIImage()
                UIGraphicsEndImageContext()
                return image
            }
            return _scaleImage(getScaledRect(newSize))
        }

        return isSameSize(newSize) ? self : scaleImage(newSize)!
    }
}

@KiritModi cevabının Swift 4.2 sürümü

func resizeImage(image: UIImage, targetSize: CGSize) -> UIImage {
    let size = image.size

    let widthRatio  = targetSize.width  / size.width
    let heightRatio = targetSize.height / size.height

    var newSize: CGSize
    if(widthRatio > heightRatio) {
        newSize = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
    } else {
        newSize = CGSize(width: size.width * widthRatio, height: size.height *      widthRatio)
    }

    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
}

resizeimage yönteminin çağrılması

let image1 = resizeimage(image: myimage.image!, withSize: CGSize(width:200, height: 200))

görüntüyü yeniden boyutlandırma yöntemi

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

Swift 4 Çözümü-

Bu işlevi kullanın

func image(with image: UIImage, scaledTo newSize: CGSize) -> UIImage {
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    drawingImageView.image = newImage
    return newImage ?? UIImage()
}

Bir işlevi çağırmak: -

image(with: predictionImage, scaledTo: CGSize(width: 28.0, height: 28.0)

burada 28.0, ayarlamak istediğiniz piksel boyutudur

Bir görüntünün boyutunu küçültmek için genel bir yöntem (Swift 5'te) burada verilmiştir. Ortaya çıkan görüntü orijinal ile aynı en boy oranına sahip olabilir veya orijinal görüntünün içinde ortalandığı hedef boyutta olabilir. Görüntü hedef boyuttan küçükse yeniden boyutlandırılmaz.

extension UIImage {
    func scaledDown(into size:CGSize, centered:Bool = false) -> UIImage {
        var (targetWidth, targetHeight) = (self.size.width, self.size.height)
        var (scaleW, scaleH) = (1 as CGFloat, 1 as CGFloat)
        if targetWidth > size.width {
            scaleW = size.width/targetWidth
        }
        if targetHeight > size.height {
            scaleH = size.height/targetHeight
        }
        let scale = min(scaleW,scaleH)
        targetWidth *= scale; targetHeight *= scale
        let sz = CGSize(width:targetWidth, height:targetHeight)
        if !centered {
            return UIGraphicsImageRenderer(size:sz).image { _ in
                self.draw(in:CGRect(origin:.zero, size:sz))
            }
        }
        let x = (size.width - targetWidth)/2
        let y = (size.height - targetHeight)/2
        let origin = CGPoint(x:x,y:y)
        return UIGraphicsImageRenderer(size:size).image { _ in
            self.draw(in:CGRect(origin:origin, size:sz))
        }
    }
}

Şimdiye kadar listelenen yanıtların tümü küçültülmüş boyutta bir görüntüyle sonuçlanıyor gibi görünüyor, ancak boyut piksel olarak ölçülmüyor. İşte bir Swift 5, piksel tabanlı yeniden boyutlandırma .

extension UIImage {
    func resize(_ max_size: CGFloat) -> UIImage {
        // adjust for device pixel density
        let max_size_pixels = max_size / UIScreen.main.scale
        // work out aspect ratio
        let aspectRatio =  size.width/size.height
        // variables for storing calculated data
        var width: CGFloat
        var height: CGFloat
        var newImage: UIImage
        if aspectRatio > 1 {
            // landscape
            width = max_size_pixels
            height = max_size_pixels / aspectRatio
        } else {
            // portrait
            height = max_size_pixels
            width = max_size_pixels * aspectRatio
        }
        // create an image renderer of the correct size
        let renderer = UIGraphicsImageRenderer(size: CGSize(width: width, height: height), format: UIGraphicsImageRendererFormat.default())
        // render the image
        newImage = renderer.image {
            (context) in
            self.draw(in: CGRect(x: 0, y: 0, width: width, height: height))
        }
        // return the image
        return newImage
    }
} 

Kullanım:

image.resize(500)

Örnek, görüntünün 1024 ve altına küçültülmesi içindir

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
    }

}

Bunu Swift 3'te uygun görüntü için kullanabilirsiniz ;

extension UIImage {
    func resizedImage(newSize: CGSize) -> UIImage {
        // Guard newSize is different
        guard self.size != newSize else { return self }

        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
        self.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
        let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return newImage
    }

    func resizedImageWithinRect(rectSize: CGSize) -> UIImage {
        let widthFactor = size.width / rectSize.width
        let heightFactor = size.height / rectSize.height

        var resizeFactor = widthFactor
        if size.height > size.width {
            resizeFactor = heightFactor
        }

        let newSize = CGSize(width: size.width/resizeFactor, height: size.height/resizeFactor)
        let resized = resizedImage(newSize: newSize)
        return resized
    }
}

Kullanım;

let resizedImage = image.resizedImageWithinRect(rectSize: CGSize(width: 1900, height: 1900))

Burada iki basit UIImageuzantı işlevine sahipsiniz :

func scaledWithMaxWidthOrHeightValue(value: CGFloat) -> UIImage? {

    let width = self.size.width
    let height = self.size.height

    let ratio = width/height

    var newWidth = value
    var newHeight = value

    if ratio > 1 {
        newWidth = width * (newHeight/height)
    } else {
        newHeight = height * (newWidth/width)
    }

    UIGraphicsBeginImageContextWithOptions(CGSize(width: newWidth, height: newHeight), false, 0)

    draw(in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight))

    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return image
}

func scaled(withScale scale: CGFloat) -> UIImage? {

    let size = CGSize(width: self.size.width * scale, height: self.size.height * scale)

    UIGraphicsBeginImageContextWithOptions(size, false, 0)

    draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))

    let image = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return image
}

Swift 5 ile güzelce çalışmak için benim kabul edilen cevabımın versiyonunu buraya atıyorum. Bu çözüm, ortaya çıkan görüntüyü açmaya zorlamaz ve onu biraz daha güvenli ve genel olarak daha temiz bir çözüm haline getirir.

extension UIImage {
    public func resized(to target: CGSize) -> UIImage? {
        let ratio = min(
            target.height / size.height, target.width / size.width
        )
        let new = CGSize(
            width: size.width * ratio, height: size.height * ratio
        )
        UIGraphicsBeginImageContextWithOptions(new, false, 1.0)
        draw(in: CGRect(origin: .zero, size: new))
        defer { UIGraphicsEndImageContext() }
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

UIImage Uzantısı Swift 5

extension UIImage {
    func resize(_ width: CGFloat, _ height:CGFloat) -> UIImage? {
        let widthRatio  = width / size.width
        let heightRatio = height / size.height
        let ratio = widthRatio > heightRatio ? heightRatio : widthRatio
        let newSize = CGSize(width: size.width * ratio, height: size.height * ratio)
        let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)
        UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

Kullanım: UIImage (). Resize (200, 300)

SWIFT 5 ile newImage = UIImage(cgImage: cgImage)

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)
                newImage = UIImage(cgImage: cgImage)
                UIGraphicsEndImageContext()

            }

            return newImage
   }