使用drawInRect调整图像大小，同时保持像Scale Aspect Fill一样的宽高比？

Question

我想用drawInRect方法调整图像的大小，但我还想保持正确的宽高比，同时完全填充给定的帧（如.ScaleAspectFill对UIViewContentMode所做的那样）。 任何人都有一个现成的答案吗？

这是我的代码（非常简单......）：

func scaled100Image() -> UIImage {
    let newSize = CGSize(width: 100, height: 100)
    UIGraphicsBeginImageContext(newSize)
    self.pictures[0].drawInRect(CGRect(x: 0, y: 0, width: 100, height: 100))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

Answer 1

好的，所以没有现成的答案......我为UIImage写了一个快速的扩展，如果你需要它可以随意使用它。

这里是：

extension UIImage {
    func drawInRectAspectFill(rect: CGRect) {
        let targetSize = rect.size
        if targetSize == CGSizeZero {
            return self.drawInRect(rect)
        }
        let widthRatio    = targetSize.width  / self.size.width
        let heightRatio   = targetSize.height / self.size.height
        let scalingFactor = max(widthRatio, heightRatio)
        let newSize = CGSize(width:  self.size.width  * scalingFactor,
                             height: self.size.height * scalingFactor)
        UIGraphicsBeginImageContext(targetSize)
        let origin = CGPoint(x: (targetSize.width  - newSize.width)  / 2, 
                             y: (targetSize.height - newSize.height) / 2)
        self.drawInRect(CGRect(origin: origin, size: newSize))
        let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        scaledImage.drawInRect(rect)
    }
}

所以在上面的例子中，你使用它：

self.pictures[0].drawInRectAspectFill(CGRect(x: 0, y: 0, width: 100, height: 100))

Answer 2

Objective-C版本，如果有人需要它（将此代码粘贴到UIIMage类别中）：

- (void) drawInRectAspectFill:(CGRect) recto {

CGSize targetSize = recto.size;
if (targetSize.width <= CGSizeZero.width && targetSize.height <= CGSizeZero.height ) {
    return  [self drawInRect:recto];
}

float widthRatio = targetSize.width  / self.size.width;
float heightRatio   = targetSize.height / self.size.height;
float scalingFactor = fmax(widthRatio, heightRatio);
CGSize newSize = CGSizeMake(self.size.width  * scalingFactor, self.size.height * scalingFactor);

UIGraphicsBeginImageContext(targetSize);

CGPoint origin = CGPointMake((targetSize.width-newSize.width)/2,(targetSize.height - newSize.height) / 2);

[self drawInRect:CGRectMake(origin.x, origin.y, newSize.width, newSize.height)];
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

[scaledImage drawInRect:recto];

}