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?
我在苹果自己的例子中找到了一个UIImage的类别,它做了同样的技巧。这是链接:https://developer.apple.com/library/ios/samplecode/sc2273/Listings/AirDropSample_UIImage_Resize_m.html。
你只需要改变电话号码:
UIGraphicsBeginImageContextWithOptions(newSize, YES, 2.0);
in imageWithImage:scaledToSize:inRect: with
UIGraphicsBeginImageContextWithOptions(newSize, NO, 2.0);
为了考虑图像中的alpha通道。
如果你只想要一个更小的图像,不关心确切的大小:
+ (UIImage *)imageWithImage:(UIImage *)image scaledToScale:(CGFloat)scale
{
UIGraphicsBeginImageContextWithOptions(self.size, YES, scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
[self drawInRect:CGRectMake(0, 0, self.size.width, self.size.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
将比例设置为0.25f将从800万相机中获得816 * 612的图像。
这里有一个UIImage+Scale的分类。
以下是斯威夫特版的保罗·林奇的回答
func imageWithImage(image:UIImage, scaledToSize newSize:CGSize) -> UIImage{
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
image.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
作为延伸:
public extension UIImage {
func copy(newSize: CGSize, retina: Bool = true) -> UIImage? {
// In next line, pass 0 to use the current device's pixel scaling factor (and thus account for Retina resolution).
// Pass 1 to force exact pixel size.
UIGraphicsBeginImageContextWithOptions(
/* size: */ newSize,
/* opaque: */ false,
/* scale: */ retina ? 0 : 1
)
defer { UIGraphicsEndImageContext() }
self.draw(in: CGRect(origin: .zero, size: newSize))
return UIGraphicsGetImageFromCurrentImageContext()
}
}
这是一个与Swift 3和Swift 4兼容的UIImage扩展,它可以将图像缩放到给定的大小
extension UIImage {
func scaledImage(withSize size: CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
defer { UIGraphicsEndImageContext() }
draw(in: CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height))
return UIGraphicsGetImageFromCurrentImageContext()!
}
func scaleImageToFitSize(size: CGSize) -> UIImage {
let aspect = self.size.width / self.size.height
if size.width / aspect <= size.height {
return scaledImage(withSize: CGSize(width: size.width, height: size.width / aspect))
} else {
return scaledImage(withSize: CGSize(width: size.height * aspect, height: size.height))
}
}
}
示例使用
let image = UIImage(named: "apple")
let scaledImage = image.scaleImageToFitSize(size: CGSize(width: 45.0, height: 45.0))