iOS 使图像适合屏幕

Question

我有一张 646x289 的图像，我试图根据其纵横比来适应屏幕。

这是我目前的做法：

控制器：

public override void ViewDidLayoutSubviews()
{
    base.ViewDidLayoutSubviews();
    _imnLogo.ContentMode = UIViewContentMode.ScaleAspectFit;
    _imnLogo.SizeToFit();
    _imnLogo.Frame = new CGRect(
        View.Bounds.Left + 2 * Globals.MarginGrid,
        View.Bounds.Top + Globals.MarginGrid,
        _scaledImage.Size.Width, _scaledImage.Size.Height);
}

public override void LoadView()
{
    base.LoadView();
    _scaledImage = MaxResizeImage(
        UIImage.FromFile("imn_logo.png"), (float) View.Bounds.Width, (float) View.Bounds.Height);

    _imnLogo = new UIImageView(_scaledImage);
    View.AddSubview(_imnLogo);
}

public UIImage MaxResizeImage(UIImage sourceImage, float maxWidth, float maxHeight)
{
    var sourceSize = sourceImage.Size;
    var maxResizeFactor = Math.Max(maxWidth / sourceSize.Width, maxHeight / sourceSize.Height);
    if (maxResizeFactor > 1) return sourceImage;

    var width = maxResizeFactor * sourceSize.Width;
    var height = maxResizeFactor * sourceSize.Height;
    UIGraphics.BeginImageContext(new SizeF((float) width, (float) height));
    sourceImage.Draw(new RectangleF(0, 0, (float) width, (float) height));
    var resultImage = UIGraphics.GetImageFromCurrentImageContext();
    UIGraphics.EndImageContext();
    return resultImage;
}

加载时，图像太大，不适合屏幕。

我也在用 C#（使用 Xamarin）构建我的所有接口，所以我需要能够使用框架和边界来做到这一点。

Answer 1

使用UIImageView 的ContentMode 来控制图像的缩放方式，您可以跳过手动调整大小：

public override void LoadView()
{
    base.LoadView();
    _imnLogo = new UIImageView(UIImage.FromFile("imn_logo.png"));
    _imnLogo.Frame = View.Frame;
    _imnLogo.ContentMode = UIViewContentMode.ScaleAspectFill;
    View.AddSubview(imageView);
    View.SendSubviewToBack(imnLogo); // Do this if you want to place other `View`s on top of the logo...
}

参考：https://developer.apple.com/reference/uikit/uiviewcontentmode