为离屏渲染移动 UWP InkStrokes

Question

我正在捕获 InkStrokes 并且需要在背景中创建笔划的缩放位图图像。无论墨水的边界框有多大，捕获的图像都需要具有统一的大小。

例如，如果绘制原始墨迹笔划并且边界框 top/left 为 100,100 且墨迹上的大小为 200,200 canvas，我希望墨迹从 0,0 开始大小为 50,50 的新渲染位图（现在忽略笔划宽度的影响）。

我已经想出如何缩放墨迹笔划（感谢）但不知道如何移动笔划。现在，我似乎必须创建一个 InkCanvas 大小的位图，渲染缩放的墨水，然后将更大的图像裁剪为正确的大小。

我已经尝试使用 InkStroke.PointTranslate 通过

var scaleMatrix = Matrix3x2.CreateScale(scale);
scaleMatrix.Translation = -offset; // top/left of ink stroke bounding box
stroke.PointTransform = scaleMatrix;

但是坐标不正确

非常感谢任何帮助。

Answer 1

您可以通过乘以矩阵来组合变换。这对我有用

var strokes = inkCanvas.InkPresenter.StrokeContainer.GetStrokes();

var boundingBox = inkCanvas.InkPresenter.StrokeContainer.BoundingRect;

var matrix1 = Matrix3x2.CreateTranslation((float)-boundingBox.X, (float)-boundingBox.Y);
var matrix2 = Matrix3x2.CreateScale(0.5f);

var builder = new InkStrokeBuilder();
var newStrokeList = new List<InkStroke>();
foreach (var stroke in strokes)
{
    newStrokeList.Add(builder.CreateStrokeFromInkPoints
        (stroke.GetInkPoints(), matrix1 * matrix2));
}

//Add the translated and scaled strokes to the inkcanvas
inkCanvas.InkPresenter.StrokeContainer.AddStrokes(newStrokeList);

Answer 2

也许我还是做错了什么，但看来您不能将 InkStrokeBuilder.CreateStrokeFromInkPoints 用于不止一种变换。我尝试了各种 combinations/approaches，就是无法正常工作。

这是我的解决方案...

 private static IList<InkStroke> GetScaledAndTransformedStrokes(IList<InkStroke> strokeList, float scale)
        {
            var builder = new InkStrokeBuilder();
            var newStrokeList = new List<InkStroke>();
            var boundingBox = strokeList.GetBoundingBox();

            foreach (var singleStroke in strokeList)
            {  
                var translateMatrix = new Matrix(1, 0, 0, 1, -boundingBox.X, -boundingBox.Y);

                var newInkPoints = new List<InkPoint>();
                var originalInkPoints = singleStroke.GetInkPoints();
                foreach (var point in originalInkPoints)
                {
                    var newPosition = translateMatrix.Transform(point.Position);
                    var newInkPoint = new InkPoint(newPosition, point.Pressure, point.TiltX, point.TiltY, point.Timestamp);
                    newInkPoints.Add(newInkPoint);
                }

                var newStroke = builder.CreateStrokeFromInkPoints(newInkPoints, new Matrix3x2(scale, 0, 0, scale, 0, 0));

                newStrokeList.Add(newStroke);
            }

            return newStrokeList;
        }

我最终不得不应用我自己的翻译转换，然后使用 builder.CreateStrokeFromInkPoints 和应用比例矩阵来获得我想要的结果。 GetBoundingBox是我自己的扩展：

 public static class RectExtensions
    {
        public static Rect CombineWith(this Rect r, Rect rect)
        {
            var top = (r.Top < rect.Top) ? r.Top : rect.Top;
            var left = (r.Left < rect.Left) ? r.Left : rect.Left;
            var bottom = (r.Bottom < rect.Bottom) ? rect.Bottom : r.Bottom;
            var right = (r.Right < rect.Right) ? rect.Right : r.Right;

            var newRect = new Rect(new Point(left, top), new Point(right, bottom));
            return newRect;
        }
    }

为离屏渲染移动 UWP InkStrokes

Moving UWP InkStrokes for Offscreen Rendering

c#

inkcanvas

uwp

uwp-xaml