Skia / SkiaSharp - 围绕它们自己的垂直轴旋转形状

问题描述

我使用下面的 OnDraw 方法生成上面的场景：

  protected override void OnDraw(SKCanvas canvas,int width,int height)
    {
        int i = 0;
        int step = 0;
        List<SKRect> rects = new List<SKRect>();

        // get the 2D equivalent of the 3D matrix
        var rotationMatrix = rotationView.Matrix;

        // get the properties of the rectangle
        var length = Math.Min(width / 6,height / 6);

        canvas.Clear(EffectMedia.Colors.XamarinLightBlue);

        foreach (var n in numbers)
        {
            var rect = new SKRect(0 + step,100 + step,100);
            rects.Add(rect);
            step += 120;
        }

        //var sideHoriz = rotationMatrix.MapPoint(new SKPoint(0,1)).Y > 0;
        var sideVert = rotationMatrix.MapPoint(new SKPoint(1,0)).X > 0;

        var paint = new SKPaint
        {
            Color = sideVert ? EffectMedia.Colors.XamarinPurple : EffectMedia.Colors.XamarinGreen,Style = SKPaintStyle.Fill,IsAntialias = true
        };

        // first do 2D translation to the center of the screen
        canvas.Translate((width - (120 * numbers.Count)) / 2,height / 2);

        // The following line is disabled because it makes the whole canvas rotate!
        // canvas.Concat(ref rotationMatrix);

        foreach (var n in numbers)
        {            
            canvas.Rotatedegrees((float)-3);
            canvas.DrawRoundRect(rects[i],30,paint);

            var shadow = SKShader.CreateLinearGradient(
                    new SKPoint(0,0),new SKPoint(0,length * 2),new[] { paint.Color.WithAlpha(127),paint.Color.WithAlpha(0) },null,SKShaderTileMode.Clamp);

            var paintShadow = new SKPaint
            {
                Shader = shadow,IsAntialias = true,BlendMode = SKBlendMode.softLight
            };

            foreach (var r in rects)
            {
                r.Offset(0,105);
                canvas.DrawRoundRect(r,paintShadow);
            }

            i++;
        }
    }

这个想法是让所有这些圆角框围绕它们自己的轴（垂直）旋转。

我尝试使用 SKPath + Transform，保存和恢复 rotationMatrix 和/或画布，但我找不到有 6 个旋转框的方法（ canvas.Concat(ref rotationMatrix); 使整个画布旋转 [*]）。

您对如何实现这一目标有任何提示吗？

注意 [*]：每 X 毫秒调用一次 rotationView.RotateYdegrees(5) 以更新 OnDraw 使用的 rotationMatrix。

解决方法

这就是我想要实现的目标，任何提示/方向都将不胜感激... :-)

以下代码围绕 Z 轴旋转这些形状：

canvas.Save();
canvas.RotateDegrees(degrees,rects[i].MidX,rects[i].MidY);
canvas.DrawRoundRect(rects[i],30,paint);
canvas.Restore();

谢谢