根据color和size生成新的图片

extension UIImage {
     public class func image(color: UIColor, size: CGSize) -> UIImage? {
        if size.width <= 0 || size.height <= 0 {
            return nil
        }
        
        let rect = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        let context = UIGraphicsGetCurrentContext()
        context?.setFillColor(color.cgColor)
        context?.fill(rect)
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image
    }
}

根据radius,corners,borderWidth,borderColor,borderLineJoin生成新的图片

extension UIImage {

      public func image(radius: CGFloat, borderWidth: CGFloat, borderColor: UIColor) -> UIImage? {
        return image(radius: radius, corners: UIRectCorner.allCorners, borderWidth: borderWidth, borderColor: borderColor, borderLineJoin: .miter)
    }

      public func image(radius: CGFloat, corners: UIRectCorner, borderWidth: CGFloat, borderColor: UIColor, borderLineJoin: CGLineJoin) -> UIImage? {
        /*
         /* Line join styles. */
         
         public enum CGLineJoin : Int32 {
         
         case miter
         
         case round
         
         case bevel
         }
         */
        
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        let context = UIGraphicsGetCurrentContext()
        let rect = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        context?.scaleBy(x: 1, y: -1)
        context?.translateBy(x: 0, y: -rect.size.height)
        
        let minSize = min(size.width, size.height)
        if borderWidth < minSize / 2 {
            let path = UIBezierPath.init(roundedRect: rect.insetBy(dx: borderWidth, dy: borderWidth), byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: borderWidth))
            path.close()
            
            context?.saveGState()
            path.addClip()
            context?.draw(cgImage!, in: rect)
            context?.restoreGState()
        }
        
        if borderWidth > 0 && borderWidth < minSize / 2 {
            let strokeInset = (floor(borderWidth*scale)+0.5) / scale
            let strokeRect = rect.insetBy(dx: strokeInset, dy: strokeInset)
            let strokeRadius = radius > scale / 2 ? radius-scale/2 : 0
            
            let path = UIBezierPath.init(roundedRect: strokeRect, byRoundingCorners: corners, cornerRadii: CGSize(width: strokeRadius, height: borderWidth))
            path.close()
            
            path.lineWidth = borderWidth
            path.lineJoinStyle = borderLineJoin
            borderColor.setStroke()
            path.stroke()
        }
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image
    }
}

图片压缩

extension UIImage {
      public func compressed(quality: CGFloat = 0.5) -> UIImage? {
        guard let data = compressedData(quality: quality) else { return nil }
        return UIImage(data: data)
    }
    
    public func compressedData(quality: CGFloat = 0.5) -> Data? {
        return UIImageJPEGRepresentation(self, quality)
    }
}

图片缩放

extension UIImage {
     public func scaled(toHeight: CGFloat, opaque: Bool = false, with orientation: UIImageOrientation? = nil) -> UIImage? {
        let scale = toHeight / size.height
        let newWidth = size.width * scale
        UIGraphicsBeginImageContextWithOptions(CGSize(width: newWidth, height: toHeight), opaque, scale)
        draw(in: CGRect(x: 0, y: 0, width: newWidth, height: toHeight))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
    
    public func scaled(toWidth: CGFloat, opaque: Bool = false, with orientation: UIImageOrientation? = nil) -> UIImage? {
        let scale = toWidth / size.width
        let newHeight = size.height * scale
        UIGraphicsBeginImageContextWithOptions(CGSize(width: toWidth, height: newHeight), opaque, scale)
        draw(in: CGRect(x: 0, y: 0, width: toWidth, height: newHeight))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

圆角图片

extension UIImage {
     public func withRoundedCorners(radius: CGFloat? = nil) -> UIImage? {
        let maxRadius = min(size.width, size.height) / 2
        let cornerRadius: CGFloat
        if let radius = radius, radius > 0 && radius <= maxRadius {
            cornerRadius = radius
        } else {
            cornerRadius = maxRadius
        }
        
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        
        let rect = CGRect(origin: .zero, size: size)
        UIBezierPath(roundedRect: rect, cornerRadius: cornerRadius).addClip()
        draw(in: rect)
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

初始化方法

extension UIImage {
     //init with color and size
     public convenience init(color: UIColor, size: CGSize) {
        UIGraphicsBeginImageContextWithOptions(size, false, 1)
        color.setFill()
        UIRectFill(CGRect(x: 0, y: 0, width: size.width, height: size.height))
        guard let image = UIGraphicsGetImageFromCurrentImageContext() else {
            self.init()
            return
        }
        UIGraphicsEndImageContext()
        guard let aCgImage = image.cgImage else {
            self.init()
            return
        }
        self.init(cgImage: aCgImage)
    }
    
    // simplified contentsOfFile: method
    public convenience init(fileNamed: String) {
        let path = UIImage.createLocalUrl(forImageNamed: fileNamed)?.path
        self.init(contentsOfFile: path!)!
    }
    
    static func createLocalUrl(forImageNamed name: String) -> URL? {
        
        let fileManager = FileManager.default
        let cacheDirectory = fileManager.urls(for: .cachesDirectory, in: .userDomainMask)[0]
        if name.contains(".jpg") {
            return cacheDirectory.appendingPathComponent(name)
        }
        let scale = UIScreen.main.scale
        var scaleName = ""
        switch scale {
        case 2:
            scaleName = name + "@2x.png"
        case 3:
            scaleName = name + "@3x.png"
        default:
            scaleName = name + ".png"
        }
        let url = cacheDirectory.appendingPathComponent("\(scaleName)")
        
        guard fileManager.fileExists(atPath: url.path) else {
            guard
                let image = UIImage(named: name),
                let data = UIImagePNGRepresentation(image)
                else { return nil }
            
            fileManager.createFile(atPath: url.path, contents: data, attributes: nil)
            return url
        }
        
        return url
    }
}

资源来自网络和日常整理，持续更新