Swift에서 이미지 크기를 조정하는 방법?

Swift에서 이미지 크기를 조정하는 방법?

저는 swift와 Parse.com 를 이용하여 iOS용 앱을 만들고 있습니다.

백엔드에 업로드하기 전에 사용자가 이미지 선택기에서 사진을 선택한 다음 선택한 이미지의 크기를 200x200픽셀로 조정할 수 있도록 하려고 합니다.

Parse.com 에는 이미지 크기 조정을 위한 코드를 제공하는 "AnyPic"이라는 인스타그램 복사 앱에 대한 튜토리얼이 있지만, 그것은 Objective-C에 있습니다.

// 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];

선택한 사진의 200x200px 버전을 Swift에서 어떻게 생성합니까?

그리고 썸네일 이미지 기능은 무엇을 하고 있습니까?

자세한 내용은 블로그 게시물 "신속하고 객관적인 C에서 이미지 크기 조정"을 참조하십시오.

아래와 같이 이미지 크기 조정 기능이 신속합니다.

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(origin: .zero, size: newSize)
    
    // 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
}

위의 기능을 사용하여 아래 코드와 같이 200*200으로 이미지 크기를 조정합니다.

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

swift3 업데이트됨

 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!
}

세부 사항

• Xcode 10.2.1(10E1001), Swift 5

링크

• https://gist.github.com/eugenebokhan/5e62a0155754ae6aa6c3c13cf1744930
• 이미지 크기 조정 기술

해결책

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
    }
}

사용.

이미지 크기 가져오기

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))
    }
}

테스트 함수

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)
}

산출량

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

Swift 4.0 및 iOS 10의 경우

    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
        }
    }

@KiritModi의 답변은 2015년이므로 Swift 3.0 버전은 다음과 같습니다.

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 5.0 및 iOS 12의 경우

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

사용:

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

Swift 4의 경우, 저는 UI 이미지에 자신을 참조하여 확장할 것입니다.

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!
  }
}

Alamofire Image(https://github.com/Alamofire/AlamofireImage) 를 사용할 수도 있습니다.

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

이전 게시물의 기능은 저에게 흐릿한 결과를 주었습니다.

최신 버전을 사용하는 Swift 5 버전 업데이트UIGraphicsImageRendererAPI.

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
        )
        let renderer = UIGraphicsImageRenderer(size: new)
        return renderer.image { _ in
            self.draw(in: CGRect(origin: .zero, size: new))
        }
    }
}

Swift 3 버전 및 확장 스타일

이 대답은 @Kirit Modi에서 왔습니다.

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!
    }
}

스위프트 4, 확장 버전, 가장자리에 흰색 선 없음.

아무도 그것을 언급하지 않는 것 같습니다 만약에image.draw()이 값을 사용하여 호출되며, 결과 이미지는 오른쪽 또는 아래쪽 가장자리에 흰색 선 아티팩트를 표시할 수 있습니다.

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
    }

비율(scaleToFill) 및 중심 영상을 고려한 Swift 5 버전:

extension UIImage {
    func resized(to newSize: CGSize) -> UIImage {
        return UIGraphicsImageRenderer(size: newSize).image { _ in
            let hScale = newSize.height / size.height
            let vScale = newSize.width / size.width
            let scale = max(hScale, vScale) // scaleToFill
            let resizeSize = CGSize(width: size.width*scale, height: size.height*scale)
            var middle = CGPoint.zero
            if resizeSize.width > newSize.width {
                middle.x -= (resizeSize.width-newSize.width)/2.0
            }
            if resizeSize.height > newSize.height {
                middle.y -= (resizeSize.height-newSize.height)/2.0
            }
            
            draw(in: CGRect(origin: middle, size: resizeSize))
        }
    }
}

스위프트 4 버전

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)!
    }
}

다음은 크기에 맞게 이미지를 다운스케일링하는 일반적인 방법(Swift 5의 경우)입니다.결과 영상의 가로 세로 비율이 원본과 같거나 원본 영상이 가운데에 있는 대상 크기일 수 있습니다.이미지가 대상 크기보다 작으면 크기가 조정되지 않습니다.

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))
        }
    }
}

UI 이미지 확장 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
    }
}

---

사용 : UIImage().resize(200, 300)

지금까지 나열된 모든 답변은 축소된 크기의 이미지를 생성하는 것처럼 보이지만 크기는 픽셀로 측정되지 않습니다.이것은 스위프트 5의 픽셀 기반 크기 조정입니다.

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
    }
} 

용도:

image.resize(500)

@KiritModi 응답의 Swift 4.2 버전

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!
}

스위프트4 솔루션

이 함수 사용

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()
}

함수 호출:-

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

여기서 28.0은 설정하려는 픽셀 크기입니다.

이미지 크기 조정 방법 호출

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

이미지 크기 조정 방법

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!
    }

에 여두가간기있습다니능이한단지의 두 .UIImage확장명:

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 - XCODE 12 -- 이미지 크기 조정 및 흰색 선 없음

저는 스위프트 5에 대해 위의 멋진 솔루션을 사용했습니다.그리고 크기가 조정된 이미지 주위에 흰색 선을 긋기 때문에 "바닥"이라는 용어를 포함하도록 한 부분을 변경했습니다.이것은 그것을 가장 가까운 픽셀이나 어떤 것으로 반올림하여 보기 좋습니다!함수가 호출될 때(마지막 줄) 이미지 이름을 중심으로 구문을 변경해야 했습니다.

//method for resizing image

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 = floor(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!
}

사용.

  let myimage = UIImage(named: "imagename")
            
  let image1 = resizeimage(image: myimage!, withSize: CGSize(width:50, height: 50)).withRenderingMode(.alwaysOriginal)

Swift 3에서 적합한 이미지에 사용할 수 있습니다.

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
    }
}

용도;

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

예는 이미지를 1024 이하로 최소화하는 것입니다.

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
    }

}

언급URL : https://stackoverflow.com/questions/31314412/how-to-resize-image-in-swift