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。
有效的方法,不拉伸图像Swift 4
// Method to resize image
func resize(image: UIImage, toScaleSize:CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(toScaleSize, true, image.scale)
image.draw(in: CGRect(x: 0, y: 0, width: toScaleSize.width, height: toScaleSize.height))
let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return scaledImage!
}
//调用方法
let resizedImage = self.resize(image: UIImage(named: "YourImageName")!, toScaleSize: CGSize(width: 290, height: 390))
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))
下面是iwasrob对上述类别的修改。它保持原始图像的纵横比,而不是扭曲它。
- (UIImage*)scaleToSizeKeepAspect:(CGSize)size {
UIGraphicsBeginImageContext(size);
CGFloat ws = size.width/self.size.width;
CGFloat hs = size.height/self.size.height;
if (ws > hs) {
ws = hs/ws;
hs = 1.0;
} else {
hs = ws/hs;
ws = 1.0;
}
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(size.width/2-(size.width*ws)/2,
size.height/2-(size.height*hs)/2, size.width*ws,
size.height*hs), self.CGImage);
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}