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?
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()
}
}
为什么这么复杂?我认为使用系统API可以达到同样的效果:
UIImage *largeImage;
CGFloat ratio = 0.4; // you want to get a new image that is 40% the size of large image.
UIImage *newImage = [UIImage imageWithCGImage:largeImage.CGImage
scale:1/ratio
orientation:largeImage.imageOrientation];
// notice the second argument, it is 1/ratio, not ratio.
唯一的问题是你应该传递目标比率的倒数作为第二个参数,因为根据文档,第二个参数指定原始图像与新缩放图像的比率。
我也见过这样做(我在UIButtons的正常和选定状态下使用,因为按钮不会调整大小来适应)。功劳归于原作者。
首先创建一个空的。h和。m文件,分别命名为uiimageresize .h和uiimageresize .m
// Put this in UIImageResizing.h
@interface UIImage (Resize)
- (UIImage*)scaleToSize:(CGSize)size;
@end
// Put this in UIImageResizing.m
@implementation UIImage (Resize)
- (UIImage*)scaleToSize:(CGSize)size {
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), self.CGImage);
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
@end
将.h文件包含在你将要使用该函数的.m文件中,然后像这样调用它:
UIImage* image = [UIImage imageNamed:@"largeImage.png"];
UIImage* smallImage = [image scaleToSize:CGSizeMake(100.0f,100.0f)];
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))
使用这个扩展
extension UIImage {
public func resize(size:CGSize, completionHandler:(resizedImage:UIImage, data:NSData?)->()) {
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), { () -> Void in
let newSize:CGSize = size
let rect = CGRectMake(0, 0, newSize.width, newSize.height)
UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
self.drawInRect(rect)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
let imageData = UIImageJPEGRepresentation(newImage, 0.5)
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completionHandler(resizedImage: newImage, data:imageData)
})
})
}
}