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シーンに複数のカーブを配置するアプリケーションがあります。ユーザーが回線を押したかどうかを検出する簡単な方法を探していました。boundingRect()複数の線を描いてintersects()いたときは不正確すぎました。ということで、縦線以外は夢のような機能を作ってみました。

selectionMarginユーザーが設定するグローバル変数です (デフォルト = 0.5)。選択チェックの精度のマージンを調整します。名前は、各サブラインの線形関数に基づいていy = ax + bます。Pos は、mousePressEvent からの位置です。

bool GraphApp::pointInPath(QPainterPath path, QPointF pos)
{
    qreal posY = pos.y();
    qreal posX = pos.x();

    for (int i = 0; i < path.elementCount()-1; ++i) {
        if (posX < path.elementAt(i + 1).x && posX > path.elementAt(i).x) {
            qreal dy = path.elementAt(i + 1).y - path.elementAt(i).y;
            qreal dx = path.elementAt(i + 1).x - path.elementAt(i).x;
            qreal a = dy / dx;
            qreal b = path.elementAt(i).y - (path.elementAt(i).x * a);

            if (selectionMargin == 0.0)
                selectionMargin = 0.5;

            qreal lowerBound = (a * posX + b) + selectionMargin;
            qreal upperBound = (a * posX + b) - selectionMargin;

            if (posY < lowerBound && posY > upperBound)
                return true;
        }
    }
    return false;
}

したがって、縦線で覆われた領域から mousePressEvent を送信すると、この関数は false を返すようです。私の最初の考えはif文です：

if (posX < path.elementAt(i + 1).x && posX > path.elementAt(i).x)

if文なしでこれを実装する方法について、他のアイデアはありますか?

また、他の人が a にand関数QPainterPathのないポイントが含まれているかどうかを確認する良い方法を見つけるのに苦労しているのを見たので、これはおそらく他の人にも使用できます:)boundingRect()intersects()

編集:私の知る限り、をcontains()使用しboundingRect()ます。だから私はそれを適切な解決策とは思わない

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1 に答える 1

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I once needed something similar than you. I needed to test two paths for similarity. Therefore I created a path from a list of points (I hope you don't need a more complex path since this solution would become extremely more difficult for general QPaintingPaths). This path is constructed using a given "tolerance", this is your selectionMargin.

The function returns a QPainterPath which "draws a region around the given polyline". This region can then be filled and would result in the same image as drawing the original polyline using a pen width of tolerance using round cap and round join options.

You can also, and this is what you want to do, check if a given point is contained in this path. Note that QPainterPath::contains checks for a point to lie within the closed region defined by the path. E.g., this closed region is empty for a single line segment and a triangle for two line segments, so this is not what you want if you use contains directly on your path (as I mentioned in the 3rd comment to your question).

QPainterPath intersectionTestPath(QList<QPointF> input, qreal tolerance)
{
    //will be the result
    QPainterPath path;

    //during the loop, p1 is the "previous" point, initially the first one
    QPointF p1 = input.takeFirst(); 

    //begin with a circle around the start point
    path.addEllipse(p1, tolerance, tolerance); 

    //input now starts with the 2nd point (there was a takeFirst)
    foreach(QPointF p2, input) 
    {
        //note: during the algorithm, the pair of points (p1, p2)
        //      describes the line segments defined by input.

        //offset = the distance vector from p1 to p2
        QPointF offset = p2 - p1;

        //normalize offset to length of tolerance
        qreal length = sqrt(offset.x() * offset.x() + offset.y() * offset.y());
        offset *= tolerance / length;

        //"rotate" the offset vector 90 degrees to the left and right
        QPointF leftOffset(-offset.y(), offset.x());
        QPointF rightOffset(offset.y(), -offset.x());

        //if (p1, p2) goes downwards, then left lies to the left and
        //right to the right of the source path segment
        QPointF left1 = p1 + leftOffset; 
        QPointF left2 = p2 + leftOffset;
        QPointF right1 = p1 + rightOffset;
        QPointF right2 = p2 + rightOffset;

        //rectangular connection from p1 to p2
        {
            QPainterPath p;
            p.moveTo(left1);
            p.lineTo(left2);
            p.lineTo(right2);
            p.lineTo(right1);
            p.lineTo(left1);
            path += p; //add this to the result path
        }

        //circle around p2
        {
            QPainterPath p;
            p.addEllipse(p2, tolerance, tolerance);
            path += p; //add this to the result path
        }

        p1 = p2;
    }

    //This does some simplification; you should use this if you call
    //path.contains() multiple times on a pre-calculated path, but
    //you won't need this if you construct a new path for every call
    //to path.contains().
    return path.simplified();
}
于 2012-07-31T12:59:19.247 に答える