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
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)
})
})
}
}
其他回答
还有另一种调整UIImage大小的方法:
// Resize to height = 100 points.
let originalImage = UIImage(named: "MyOriginalImage")!
let resizingFactor = 100 / originalImage.size.height
let newImage = UIImage(cgImage: originalImage.cgImage!, scale: originalImage.scale / resizingFactor, orientation: .up)
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)
})
})
}
}
对Paul代码的改进将使你在带有视网膜显示屏的iPhone上获得清晰的高分辨率图像。否则按比例缩小时就会模糊。
+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
if ([[UIScreen mainScreen] scale] == 2.0) {
UIGraphicsBeginImageContextWithOptions(newSize, YES, 2.0);
} else {
UIGraphicsBeginImageContext(newSize);
}
} else {
UIGraphicsBeginImageContext(newSize);
}
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
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()
}
}
正确的Swift 3.0 iOS 10+解决方案:使用ImageRenderer和闭包语法:
func imageWith(newSize: CGSize) -> UIImage {
let image = UIGraphicsImageRenderer(size: newSize).image { _ in
draw(in: CGRect(origin: .zero, size: newSize))
}
return image.withRenderingMode(renderingMode)
}
这是Objective-C版本:
@implementation UIImage (ResizeCategory)
- (UIImage *)imageWithSize:(CGSize)newSize
{
UIGraphicsImageRenderer *renderer = [[UIGraphicsImageRenderer alloc] initWithSize:newSize];
UIImage *image = [renderer imageWithActions:^(UIGraphicsImageRendererContext*_Nonnull myContext) {
[self drawInRect:(CGRect) {.origin = CGPointZero, .size = newSize}];
}];
return [image imageWithRenderingMode:self.renderingMode];
}
@end
