使用drawInRect时UIImage Aspect Fit？ [英] UIImage Aspect Fit when using drawInRect?

问题描述

UIView提供方面适合内容模式。但是，我是UIView的子类，并希望使用具有宽高比的drawInRect绘制UIImage。有没有办法让我在不使用UIImageView的情况下访问该功能？

UIView provides for the "aspect fit" content mode. However, I've subclasses UIView and would like to draw a UIImage using drawInRect with an aspect fit. Is there any way for me to access that functionality without using a UIImageView?

推荐答案

这个数学有点毛茸茸，但幸运的是，这是我之前准备的解决方案：

The math for that is a little bit hairy, but fortunately, here's a solution I prepared earlier:

- (UIImage *)imageScaledToSize:(CGSize)size
{
    //create drawing context
    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);

    //draw
    [self drawInRect:CGRectMake(0.0f, 0.0f, size.width, size.height)];

    //capture resultant image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

- (UIImage *)imageScaledToFitSize:(CGSize)size
{
    //calculate rect
    CGFloat aspect = self.size.width / self.size.height;
    if (size.width / aspect <= size.height)
    {
        return [self imageScaledToSize:CGSizeMake(size.width, size.width / aspect)];
    }
    else
    {
        return [self imageScaledToSize:CGSizeMake(size.height * aspect, size.height)];
    }
}

第一个函数相当于scale to fill ，第二个（调用第一个）相当于纵横比。这些方法是作为UIImage上的类别编写的，所以要在另一个类中使用它们，你需要通过将图像作为第二个参数传递来调整它们（或者像我一样在UIImage上创建一个类别）。

The first function is equivalent to "scale to fill", the second (which calls the first) is equivalent to "aspect fit". These methods were written as a category on UIImage so to use them from within another class you'll need to tweak them by passing the image in as a second parameter (or just make a category on UIImage like I did).

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