CODEWITHSUNDEEP
c++qtpolygonintersection
Marcus Riemer
Marcus Riemer

Reputation: 7728

Finding fully contained squares in a QPolygon?

I am looking for an approach to find a set of squares that are fully contained inside a QPolygon, which is not necessarily convex. My naive approach so far looks like this:

QRectF boundingRect(mShape->boundingRect());
for (int x = boundingRect.x() - 1; x < boundingRect.width(); x++)
{
    for (int y = boundingRect.y() - 1; y < boundingRect.height(); y++)
    {
        QRectF rect(x, y, 1, 1);
        QPolygonF cell(rect);
        QPolygonF intersection = mShape->polygon().intersected(cell);
        if (!intersection.empty())
        {
            // Cell is fully contained
        }
    }
}

When I visualise the result, it looks like this:

Cells intersecting with the polygon are not left out

This is almost what I want, except that the cells intersecting with the "outline" of the polygon shouldn't be there. Does anyone have a nice idea how I could construct a set of squares that are entirely "inside" the polygon?

Upvotes: 0

Views: 1086

Answers (1)

john
john

Reputation: 88017

Assuming that the larger polygon is convex (it is in your example), it should be sufficient to check that all four corners of your square are inside the larger polygon. Use the containsPoint method on the larger polygon.

Upvotes: 1

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