在我的iPhone应用程序中，我用相机拍了一张照片，然后我想把它调整为290*390像素。我用这个方法来调整图像的大小:
UIImage *newImage = [image _imageScaledToSize:CGSizeMake(290, 390)
interpolationQuality:1];
它工作得很好，但它是一个没有记录的功能，所以我不能再在iPhone OS4上使用它了。
所以…调整UIImage大小最简单的方法是什么?
当前回答
对于Swift 5:
extension UIImage {
func resized(to newSize: CGSize) -> UIImage? {
UIGraphicsBeginImageContextWithOptions(newSize, false, 0)
defer { UIGraphicsEndImageContext() }
draw(in: CGRect(origin: .zero, size: newSize))
return UIGraphicsGetImageFromCurrentImageContext()
}
}
其他回答
Rogerio Chaves的回答是一个快速扩展
func scaledTo(size: CGSize) -> UIImage{
UIGraphicsBeginImageContextWithOptions(size, false, 0.0);
self.draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
}
还有额外的好处
func scaledTo(height: CGFloat) -> UIImage{
let width = height*self.size.width/self.size.height
return scaledTo(size: CGSize(width: width, height: height))
}
Swift 2.0:
let image = UIImage(named: "imageName")
let newSize = CGSize(width: 10, height: 10)
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
image?.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
let imageResized = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
当使用iOS 15或更新版本时，你可以使用UIImage的新的prepareThumbnail方法:
sourceImage.prepareThumbnail(of: thumbnailSize) { thumbnail in
// Do something with the resized image
DispatchQueue.main.async {
cell.imageView?.image = thumbnail
}
}
更多信息: https://developer.apple.com/documentation/uikit/uiimage/3750845-preparethumbnail
有时你的图像的比例大于1，所以调整图像大小会使图像意想不到。这就是这种情况下的解。
extension UIImage {
func resizeTo(newSize: CGSize) -> UIImage {
// Important thing here
let format = UIGraphicsImageRendererFormat()
format.scale = 1
let image = UIGraphicsImageRenderer(size: newSize, format: format).image { _ in
draw(in: CGRect(origin: .zero, size: newSize))
}
return image.withRenderingMode(renderingMode)
}
}
使用这个扩展，如果你需要调整宽度/高度仅与纵横比。
extension UIImage {
func resize(to size: CGSize) -> UIImage {
return UIGraphicsImageRenderer(size: size).image { _ in
draw(in: CGRect(origin: .zero, size: size))
}
}
func resize(width: CGFloat) -> UIImage {
return resize(to: CGSize(width: width, height: width / (size.width / size.height)))
}
func resize(height: CGFloat) -> UIImage {
return resize(to: CGSize(width: height * (size.width / size.height), height: height))
}
}
