Table Of Contents

• Gesture recognition
  • Gesture
    • Gesture.add_stroke()
    • Gesture.dot_product()
    • Gesture.get_rigid_rotation()
    • Gesture.get_score()
    • Gesture.normalize()
  • GestureDatabase
    • GestureDatabase.add_gesture()
    • GestureDatabase.find()
    • GestureDatabase.gesture_to_str()
    • GestureDatabase.str_to_gesture()
  • GestureStroke
    • GestureStroke.add_point()
    • GestureStroke.center_stroke()
    • GestureStroke.normalize_stroke()
    • GestureStroke.points_distance()
    • GestureStroke.scale_stroke()
    • GestureStroke.stroke_length()

Gesture recognition

This class allows you to easily create new gestures and compare them:

from kivy.gesture import Gesture, GestureDatabase

# Create a gesture
g = Gesture()
g.add_stroke(point_list=[(1,1), (3,4), (2,1)])
g.normalize()

# Add it to the database
gdb = GestureDatabase()
gdb.add_gesture(g)

# And for the next gesture, try to find it!
g2 = Gesture()
# ...
gdb.find(g2)

Warning

You don’t really want to do this: it’s more of an example of how to construct gestures dynamically. Typically, you would need a lot more points, so it’s better to record gestures in a file and reload them to compare later. Look in the examples/gestures directory for an example of how to do that.

class kivy.gesture.Gesture(tolerance=None)

Bases: builtins.object

A python implementation of a gesture recognition algorithm by Oleg Dopertchouk: http://www.gamedev.net/reference/articles/article2039.asp

Implemented by Jeiel Aranal (chemikhazi@gmail.com), released into the public domain.

add_stroke(point_list=None)

Adds a stroke to the gesture and returns the Stroke instance. Optional point_list argument is a list of the mouse points for the stroke.

dot_product(comparison_gesture)

Calculates the dot product of the gesture with another gesture.

get_rigid_rotation(dstpts)

Extract the rotation to apply to a group of points to minimize the distance to a second group of points. The two groups of points are assumed to be centered. This is a simple version that just picks an angle based on the first point of the gesture.

get_score(comparison_gesture, rotation_invariant=True)

Returns the matching score of the gesture against another gesture.

normalize(stroke_samples=32)

Runs the gesture normalization algorithm and calculates the dot product with self.

class kivy.gesture.GestureDatabase

Bases: builtins.object

Class to handle a gesture database.

add_gesture(gesture)

Add a new gesture to the database.

find(gesture, minscore=0.9, rotation_invariant=True)

Find a matching gesture in the database.

gesture_to_str(gesture)

Convert a gesture into a unique string.

str_to_gesture(data)

Convert a unique string to a gesture.

class kivy.gesture.GestureStroke

Bases: builtins.object

Gestures can be made up of multiple strokes.

add_point(x=x_pos, y=y_pos)

Adds a point to the stroke.

center_stroke(offset_x, offset_y)

Centers the stroke by offsetting the points.

normalize_stroke(sample_points=32)

Normalizes strokes so that every stroke has a standard number of points. Returns True if stroke is normalized, False if it can’t be normalized. sample_points controls the resolution of the stroke.

points_distance(point1=GesturePoint, point2=GesturePoint)

Returns the distance between two GesturePoints.

scale_stroke(scale_factor=float)

Scales the stroke down by scale_factor.

stroke_length(point_list=None)

Finds the length of the stroke. If a point list is given, finds the length of that list.

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