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
给我的萨玛瑞恩同胞们，这是萨玛琳。iOS c#版本的@Paul Lynch回答。
private UIImage ResizeImage(UIImage image, CGSize newSize)
{
UIGraphics.BeginImageContextWithOptions(newSize, false, 0.0f);
image.Draw(new CGRect(0, 0, newSize.Width, newSize.Height));
UIImage newImage = UIGraphics.GetImageFromCurrentImageContext();
UIGraphics.EndImageContext();
return newImage;
}
其他回答
Swift 4和iOS 10+的更紧凑版本:
extension UIImage {
func resized(to size: CGSize) -> UIImage {
return UIGraphicsImageRenderer(size: size).image { _ in
draw(in: CGRect(origin: .zero, size: size))
}
}
}
用法:
let resizedImage = image.resized(to: CGSize(width: 50, height: 50))
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;
}
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。
当使用iOS 15或更新版本时，你可以使用UIImage的新的prepareThumbnail方法:
sourceImage.prepareThumbnail(of: thumbnailSize) { thumbnail in
// Do something with the resized image
DispatchQueue.main.async {
cell.imageView?.image = thumbnail
}
}
更多信息: https://developer.apple.com/documentation/uikit/uiimage/3750845-preparethumbnail
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;
}
