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?
@Paul Lynch的回答很好,但它会改变图像比例。
如果你不想改变图像比例,并且仍然希望新的图像适合新的大小,试试这个。
+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
// calculate a new size which ratio is same to original image
CGFloat ratioW = image.size.width / newSize.width;
CGFloat ratioH = image.size.height / newSize.height;
CGFloat ratio = image.size.width / image.size.height;
CGSize showSize = CGSizeZero;
if (ratioW > 1 && ratioH > 1) {
if (ratioW > ratioH) {
showSize.width = newSize.width;
showSize.height = showSize.width / ratio;
} else {
showSize.height = newSize.height;
showSize.width = showSize.height * ratio;
}
} else if (ratioW > 1) {
showSize.width = showSize.width;
showSize.height = showSize.width / ratio;
} else if (ratioH > 1) {
showSize.height = showSize.height;
showSize.width = showSize.height * ratio;
}
//UIGraphicsBeginImageContext(newSize);
// In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution).
// Pass 1.0 to force exact pixel size.
UIGraphicsBeginImageContextWithOptions(showSize, NO, 0.0);
[image drawInRect:CGRectMake(0, 0, showSize.width, showSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;}
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))
}
(兼容Swift 4) iOS 10+和iOS < 10解决方案(如果可能,使用UIGraphicsGetImageFromCurrentImageContext)
/// Resizes an image
///
/// - Parameter newSize: New size
/// - Returns: Resized image
func scaled(to newSize: CGSize) -> UIImage {
let rect = CGRect(origin: .zero, size: newSize)
if #available(iOS 10, *) {
let renderer = UIGraphicsImageRenderer(size: newSize)
return renderer.image { _ in
self.draw(in: rect)
}
} else {
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
self.draw(in: rect)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage!
}
}
斯威夫特5:
func imageWithImage(_ image: UIImage?, scaledToSize newSize: CGSize) -> UIImage? {
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
image?.draw(in: CGRect(x: 0.0, y: 0.0, width: newSize.width, height: newSize.height))
let newImage: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
用法:
let img: UIImage? = imageWithImage(UIImage(named: "DefaultAvatar"), scaledToSize:CGSize(width: 20.0, height: 20.0))