UIImageView：结合UIViewContentModeScaleAspectFit和UIViewContentModeBottom

Question

有没有办法避免UIImageView图像拉伸并同时将其与底部对齐？ 基本上我想获得如果可以组合UIViewContentModeScaleAspectFit和UIViewContentModeBottom contentMode s会发生什么。

Answer 1

基于约束的方法

您需要约束UIImageView的left ， right和bottom ，同时确保大小的比例与它显示的UIImage相同。

UIImage *image; // allocate image object here
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
[parent addSubview:imageView]; // add imageView to proper view with addSubview: here
UIView *superview = imageView.superview; // match width and bottom of self.superview
CGFloat ratio = image.size.width / image.size.height;

NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:imageView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeLeft multiplier:1.f constant:0.f];
NSLayoutConstraint *bottomConstraint = [NSLayoutConstraint constraintWithItem:imageView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeBottom multiplier:1.f constant:0.f];
NSLayoutConstraint *rightConstraint = [NSLayoutConstraint constraintWithItem:imageView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeRight multiplier:1.f constant:0.f];
NSLayoutConstraint *ratioConstraint = [NSLayoutConstraint constraintWithItem:imageView
                                                                    attribute:NSLayoutAttributeWidth
                                                                    relatedBy:NSLayoutRelationEqual
                                                                       toItem:imageView
                                                                    attribute:NSLayoutAttributeHeight
                                                                   multiplier:ratio
                                                                     constant:1.f];
[imageView addConstraint:ratioConstraint];
[superview addConstraints:@[leftConstraint, bottomConstraint, rightConstraint]];

这将模拟UIViewContentModeScaleAspectFit和UIViewContentModeBottom的组合，但也会调整UIImageView的高度。

Answer 2

我自己找到了解决方案。 此代码将UIImageView大小调整为其image的大小，并将其移动到其超级视图的底部。

CGSize initialImageSize = imageView.size;

CGSize imageSize = imageView.image.size;
CGFloat aspectRatio = imageSize.width / imageSize.height;

CGRect imageFrame = imageView.frame;

if (initialImageSize.width / aspectRatio <= initialImageSize.height) {
    imageFrame.size.width = initialImageSize.width;
    imageFrame.size.height = imageFrame.size.width / aspectRatio;
} else {
    imageFrame.size.height = initialImageSize.height;
    imageFrame.size.width = imageFrame.size.height * aspectRatio;
}

CGRect parentFrame = imageView.superview.frame;
imageFrame.origin.y = (parentFrame.origin.y + parentFrame.size.height) - imageFrame.size.height;

imageView.frame = imageFrame;

Answer 3

我的解决方案

    float newwidth;
    float newheight;

    if (image.size.height>=image.size.width){
        newheight=imageview.frame.size.height;
        newwidth=(image.size.width/image.size.height)*newheight;

        if(newwidth>imageview.frame.size.width){
            float diff=imageview.frame.size.width-newwidth;
            newheight=newheight+diff/newheight*newheight;
            newwidth=imageview.frame.size.width;
        }

    }
    else{
        newwidth=imageview.frame.size.width;
        newheight=(image.size.height/image.size.width)*newwidth;

        if(newheight>imageview.frame.size.height){
            float diff=imageview.frame.size.height-newheight;
            newwidth=newwidth+diff/newwidth*newwidth;
            newheight=imageview.frame.size.height;
        }
    }

Answer 4

我发现了一种更简单的方法。

imageView.contentMode = .Bottom
imageView.clipToBounds = true

这将阻止图像调整大小，无论它受限于什么帧。而clipToBounds部分很重要，因为它可以防止非调整大小的图像超出imageView边界。

Answer 5

晚到党，但一个简单的解决方案。 在UIImageView上：

• 使用contentMode属性定位图像。 （在当前案例中为UIView.ContentMode.bottom）
• 使用UIImageView的contentScaleFactor属性在内容视图中缩放图像。

这将保持纵横比，只需计算您需要的比例。 对于scaleAspectFit：

yourImageView.contentMode = UIView.ContentMode.bottom let relWidthScale = yourImage.size.width/yourImageView.frame.width let relHeightScale = yourImage.size.height/yourImageView.frame.height yourImageView.contentScaleFactor = min(relWidthScale,relHeightScale)

如果UIImageView更改大小，您可以通过向UIImageView或其容器的bounds属性添加观察者来更新比例。