Ios 图像缩放比例

我有这样一个形象：

我想将这个图像调整到一个特定的宽度：比如说200px，在这里也应该计算高度。（因此图像应保持其宽度与高度比例）

到目前为止，我只得到了这些：

extension UIImage {
    func resize(newSize1: CGSize) -> UIImage {
        let size = self.size
        let widthRatio  = newSize1.width  / size.width
        let heightRatio = newSize1.height / size.height

        var newSize2: CGSize
        if(widthRatio > heightRatio) {
            newSize2 = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
        } else {
            newSize2 = CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
        }
        let rect = CGRect(x: 0, y: 0, width: newSize2.width, height: newSize2.height)
        UIGraphicsBeginImageContextWithOptions(newSize2, false, 1.0)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage2!
    }
}

但是这个函数需要一个

CGSize

size参数（宽度和高度），但是我只想得到一个接受宽度参数的函数

如何编辑我的代码以解决我的问题？
非常感谢您的帮助

：）

---

注意：UIImage应该获得更小的分辨率（更少的像素），而不是图像视图本身

您可以根据图像的宽度和纵横比计算所需的高度。这同样适用于高度参数。以下是

UIImage

的扩展示例

extension UIImage {
func resize(width: CGFloat) -> UIImage {
    let height = (width/self.size.width)*self.size.height
    return self.resize(size: CGSize(width: width, height: height))
}

func resize(height: CGFloat) -> UIImage {
    let width = (height/self.size.height)*self.size.width
    return self.resize(size: CGSize(width: width, height: height))
}

func resize(size: CGSize) -> UIImage {
    let widthRatio  = size.width/self.size.width
    let heightRatio = size.height/self.size.height
    var updateSize = size
    if(widthRatio > heightRatio) {
        updateSize = CGSize(width:self.size.width*heightRatio, height:self.size.height*heightRatio)
    } else if heightRatio > widthRatio {
        updateSize = CGSize(width:self.size.width*widthRatio,  height:self.size.height*widthRatio)
    }
    UIGraphicsBeginImageContextWithOptions(updateSize, false, UIScreen.main.scale)
    self.draw(in: CGRect(origin: .zero, size: updateSize))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage!
}

---

}

您可以根据图像的宽度和纵横比计算所需的高度。这同样适用于高度参数。以下是

UIImage

的扩展示例

extension UIImage {
func resize(width: CGFloat) -> UIImage {
    let height = (width/self.size.width)*self.size.height
    return self.resize(size: CGSize(width: width, height: height))
}

func resize(height: CGFloat) -> UIImage {
    let width = (height/self.size.height)*self.size.width
    return self.resize(size: CGSize(width: width, height: height))
}

func resize(size: CGSize) -> UIImage {
    let widthRatio  = size.width/self.size.width
    let heightRatio = size.height/self.size.height
    var updateSize = size
    if(widthRatio > heightRatio) {
        updateSize = CGSize(width:self.size.width*heightRatio, height:self.size.height*heightRatio)
    } else if heightRatio > widthRatio {
        updateSize = CGSize(width:self.size.width*widthRatio,  height:self.size.height*widthRatio)
    }
    UIGraphicsBeginImageContextWithOptions(updateSize, false, UIScreen.main.scale)
    self.draw(in: CGRect(origin: .zero, size: updateSize))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage!
}

---

}

对于Swift 4和Swift 3，请使用下面的

UIImage

扩展来调整图像大小。它是根据给定的宽度计算的高度

extension UIImage {
    func resized(toWidth width: CGFloat) -> UIImage? {
        let canvasSize = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
        UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
        defer { UIGraphicsEndImageContext() }
        draw(in: CGRect(origin: .zero, size: canvasSize))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

---

对于Swift 4和Swift 3，使用以下

UIImage

扩展来调整图像大小。它是根据给定的宽度计算的高度

extension UIImage {
    func resized(toWidth width: CGFloat) -> UIImage? {
        let canvasSize = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
        UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
        defer { UIGraphicsEndImageContext() }
        draw(in: CGRect(origin: .zero, size: canvasSize))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

这不起作用（不保持比例因子！）这不起作用（不保持比例因子！）