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
@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;}
其他回答
@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;}
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)
})
})
}
}
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)];
Swift 2.0:
let image = UIImage(named: "imageName")
let newSize = CGSize(width: 10, height: 10)
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
image?.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
let imageResized = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
这里是我的一些冗长的Swift代码
func scaleImage(image:UIImage, toSize:CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(toSize, false, 0.0);
let aspectRatioAwareSize = self.aspectRatioAwareSize(image.size, boxSize: toSize, useLetterBox: false)
let leftMargin = (toSize.width - aspectRatioAwareSize.width) * 0.5
let topMargin = (toSize.height - aspectRatioAwareSize.height) * 0.5
image.drawInRect(CGRectMake(leftMargin, topMargin, aspectRatioAwareSize.width , aspectRatioAwareSize.height))
let retVal = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return retVal
}
func aspectRatioAwareSize(imageSize: CGSize, boxSize: CGSize, useLetterBox: Bool) -> CGSize {
// aspect ratio aware size
// http://stackoverflow.com/a/6565988/8047
let imageWidth = imageSize.width
let imageHeight = imageSize.height
let containerWidth = boxSize.width
let containerHeight = boxSize.height
let imageAspectRatio = imageWidth/imageHeight
let containerAspectRatio = containerWidth/containerHeight
let retVal : CGSize
// use the else at your own risk: it seems to work, but I don't know
// the math
if (useLetterBox) {
retVal = containerAspectRatio > imageAspectRatio ? CGSizeMake(imageWidth * containerHeight / imageHeight, containerHeight) : CGSizeMake(containerWidth, imageHeight * containerWidth / imageWidth)
} else {
retVal = containerAspectRatio < imageAspectRatio ? CGSizeMake(imageWidth * containerHeight / imageHeight, containerHeight) : CGSizeMake(containerWidth, imageHeight * containerWidth / imageWidth)
}
return retVal
}
