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Helper functions

psychopy.visual.helpers.pointInPolygon(x, y, poly)

Determine if a point is inside a polygon; returns True if inside.

(x, y) is the point to test. poly is a list of 3 or more vertices as (x,y) pairs. If given an object, such as a ShapeStim, will try to use its vertices and position as the polygon.

Same as the .contains() method elsewhere.

psychopy.visual.helpers.polygonsOverlap(poly1, poly2)

Determine if two polygons intersect; can fail for very pointy polygons.

Accepts two polygons, as lists of vertices (x,y) pairs. If given an object with with (vertices + pos), will try to use that as the polygon.

Checks if any vertex of one polygon is inside the other polygon. Same as the .overlaps() method elsewhere.


We implement special handling for the Line stimulus as it is not a proper polygon. We do not check for class instances because this would require importing of visual.Line, creating a circular import. Instead, we assume that a “polygon” with only two vertices is meant to specify a line. Pixels between the endpoints get interpolated before testing for overlap.

psychopy.visual.helpers.groupFlipVert(flipList, yReflect=0)

Reverses the vertical mirroring of all items in list flipList.

Reverses the .flipVert status, vertical (y) positions, and angular rotation (.ori). Flipping preserves the relations among the group’s visual elements. The parameter yReflect is the y-value of an imaginary horizontal line around which to reflect the items; default = 0 (screen center).

Typical usage is to call once prior to any display; call again to un-flip. Can be called with a list of all stim to be presented in a given routine.

Will flip a) all psychopy.visual.xyzStim that have a setFlipVert method, b) the y values of .vertices, and c) items in n x 2 lists that are mutable (i.e., list, np.array, no tuples): [[x1, y1], [x2, y2], …]