从相应大小的 UIImageView 中检索 UIImage

Question

如何从imageView 检索图像，其大小与显示（给定内容模式）一样，而不是根据本机属性的大小？

代码：

UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, WID, WID)];
imageView.center = CGPointMake(point.x, point.y + Y_OFFSET);
imageView.image = [UIImage imageNamed:@"img"];
imageView.contentMode = UIViewContentModeScaleAspectFit; 

Answer 1

你必须重新绘制图像然后保存它。

// Image frame size
CGSize size = imageView.bounds.size;
// Grab a new CGContext
UIGraphicsBeginImageContextWithOptions(size, false, 0.0);
// Draw the image
[image drawInRect:CGRectMake(0, 0, size.width, size.height)];
// Grab the new image
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

上面的代码在框架中绘制图像，拉伸到边界。如果您想要任何其他的绘制方式，您必须自己计算它们并将所需的内容放入“绘制图像”代码行中。

例如，对于方面拟合，请查看以下算法：

- (CGRect) aspectFittedRect:(CGSize)inSize max:(CGRect)maxRect {
    float originalAspectRatio = inSize.width / inSize.height;
    float maxAspectRatio = maxRect.size.width / maxRect.size.height;

    CGRect newRect = maxRect;
    if (originalAspectRatio > maxAspectRatio) { // scale by width
        newRect.size.height = maxRect.size.height * inSize.height / inSize.width;
        newRect.origin.y += (maxRect.size.height - newRect.size.height)/2.0;
    } else {
        newRect.size.width = maxRect.size.height  * inSize.width / inSize.height;
        newRect.origin.x += (maxRect.size.width - newRect.size.width)/2.0;
    }

    return CGRectIntegral(newRect);
}

只需将imageView.image.size 作为inSize 和imageView.bounds 作为maxRect 传递。

来源： http://iphonedevsdk.com/forum/iphone-sdk-development-advanced-discussion/15001-aspect-fit-algorithm.html