如何在 Xamarin Android 中合并两个图像并以与 iOS 的 CGRect 相同的方式定位它？

Question

像这样在我的项目中成功取出资源文件夹中的两张图片。

string BackGroundImage = "background_image";
string ObjectImage = "object_image";

var TheBackGroundImage = BitmapFactory.DecodeResource(Resources, Resources.GetIdentifier(BackGroundImage, "drawable", PackageName));
var TheObjectImage = BitmapFactory.DecodeResource(Resources, Resources.GetIdentifier(ObjectImage, "mipmap", PackageName));

之后我所做的是非常棘手的部分，我不知道如何完全正确。我尝试做的是创建一个以 BackgroundImage 为基础的新位图。然后我用我的第二个图像（ObjectImage）创建一个画布，该图像将位于 BackgroundImage 之上，并尝试将它们合并在一起。

Bitmap Result = Bitmap.CreateBitmap(TheBackGroundImage.Width, TheBackGroundImage.Height, TheBackGroundImage.GetConfig());
Canvas canvas = new Canvas(Result);
canvas.DrawBitmap(ObjectImage, new Matrix(), null);
canvas.DrawBitmap(ObjectImage, 79, 79, null);

这不像预期的那样工作，帆布是要走的路还是我应该看看其他东西？

如果我们看看我的 iOS 解决方案，我会这样做：

            UIImage PhoneImage = UIImage.FromFile(PhonePath);
            UIImage IconImage = UIImage.FromFile(IconPath);
            UIImage ResultImage;

            CGSize PhoneSize = PhoneImage.Size;
            CGSize IconSize = IconImage.Size;

            UIGraphics.BeginImageContextWithOptions(IconSize, false, IconImage.CurrentScale); //UIGraphics.BeginImageContextWithOptions(IconSize, false, IconImage.CurrentScale);
            UIGraphics.BeginImageContext(PhoneSize);

            CGRect Frame = (new CoreGraphics.CGRect(25, 29.5, 79, 79));
            UIBezierPath RoundImageCorner = new UIBezierPath();
            RoundImageCorner = UIBezierPath.FromRoundedRect(Frame, cornerRadius: 15);

            PhoneImage.Draw(PhoneImage.AccessibilityActivationPoint);
            RoundImageCorner.AddClip();
            IconImage.Draw(Frame);

            UIColor.LightGray.SetStroke();
            RoundImageCorner.LineWidth = 2;
            RoundImageCorner.Stroke();

            ResultImage = UIGraphics.GetImageFromCurrentImageContext();
            UIGraphics.EndImageContext();

            var documentsDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
            string jpgFilename = System.IO.Path.Combine(documentsDirectory, "app.png");

            NSData image = ResultImage.AsPNG();

而且它在我的第二张图片周围也可以很好地使用边框。

如何调整我的代码以成功地将两个图像合并在一起并将第二个图像定位为最好像 CGRect 一样？

Answer 1

试试这个：

public Bitmap mergeBitmap(Bitmap backBitmap, Bitmap frontBitmap)
{
    Bitmap bitmap = backBitmap.Copy(Bitmap.Config.Argb8888, true);
    Canvas canvas = new Canvas(bitmap);
    Rect baseRect = new Rect(0, 0, backBitmap.Width, backBitmap.Height);
    Rect frontRect = new Rect(0, 0, frontBitmap.Width, frontBitmap.Height);
    canvas.DrawBitmap(frontBitmap, frontRect, baseRect, null);
    return bitmap;
}

更新：

Here 是DrawBitmap 方法的介绍。我在方法中添加注释。

    public Bitmap mergeBitmap(Bitmap backBitmap, Bitmap frontBitmap)
    {
        Bitmap bitmap = backBitmap.Copy(Bitmap.Config.Argb8888, true);
        Canvas canvas = new Canvas(bitmap);

        //this Rect will decide which part of your frontBitmap will be drawn,
        //(0,0,frontBitmap.Width, frontBitmap.Height) means that the whole of frontBitmap will be drawn,
        //(0,0,frontBitmap.Width/2, frontBitmap.Height/2) means that the half of frontBitmap will be drawn.
        Rect frontRect = new Rect(0, 0, frontBitmap.Width, frontBitmap.Height);

        //this Rect will decide where the frontBitmap will be drawn on the backBitmap,
        //(200, 200, 200+ frontBitmap.Width, 200+frontBitmap.Height) means that
        //the fontBitmap will drawn into the Rect which left is 200, top is 200, and its width and
        //height are your frontBitmap's width and height.
        //I suggest the baseRect's width and height should be your fontBitmap's width and height,
        //or, your fontBitmap will be stretched or shrunk.
        Rect baseRect = new Rect(200, 200, 200+ frontBitmap.Width, 200+frontBitmap.Height);

        canvas.DrawBitmap(frontBitmap, frontRect, baseRect, null);
        return bitmap;
    }