sdl2.ext.algorithms - Useful Algorithms

This module contains some useful algorithms for working with shapes and surfaces. At present it contains functions for clipping lines to fit within a set of 2D boundaries and for determining whether a point falls along a given line.

sdl2.ext.algorithms.cohensutherland(left, top, right, bottom, x1, y1, x2, y2)[source]

Clips a line to a rectangular area.

This implements the Cohen-Sutherland line clipping algorithm. left, top, right and bottom define the bounds of the clipping area, by which the line from (x1, y1) to (x2, y2) will be clipped.

Parameters:
  • left (int) – The left boundary of the clipping area.
  • top (int) – The top boundary of the clipping area.
  • right (int) – The right boundary of the clipping area.
  • bottom (int) – The bottom boundary of the clipping area.
  • x1 (int) – The x-coordinate of the starting point of the line.
  • y1 (int) – The y-coordinate of the starting point of the line.
  • x2 (int) – The x-coordinate of the end point of the line.
  • y2 (int) – The y-coordinate of the end point of the line.
Returns:

The start and end coordinates of the clipped line in the form (cx1, cy1, cx2, cy2). If the line does not intersect with the rectangular clipping area, all 4 values will be None.
Return type:

tuple
sdl2.ext.algorithms.liangbarsky(left, top, right, bottom, x1, y1, x2, y2)[source]

Clips a line to a rectangular area.

This implements the Liang-Barsky line clipping algorithm. left, top, right and bottom define the bounds of the clipping area, by which the line from (x1, y1) to (x2, y2) will be clipped.

Parameters:
  • left (int) – The left boundary of the clipping area.
  • top (int) – The top boundary of the clipping area.
  • right (int) – The right boundary of the clipping area.
  • bottom (int) – The bottom boundary of the clipping area.
  • x1 (int) – The x-coordinate of the starting point of the line.
  • y1 (int) – The y-coordinate of the starting point of the line.
  • x2 (int) – The x-coordinate of the end point of the line.
  • y2 (int) – The y-coordinate of the end point of the line.
Returns:

The start and end coordinates of the clipped line in the form (cx1, cy1, cx2, cy2). If the line does not intersect with the rectangular clipping area, all 4 values will be None.
Return type:

tuple
sdl2.ext.algorithms.clipline(l, t, r, b, x1, y1, x2, y2, method='liangbarsky')[source]

Clips a line to a rectangular area using a given method.

Parameters:
  • l (int) – The left boundary of the clipping area.
  • t (int) – The top boundary of the clipping area.
  • r (int) – The right boundary of the clipping area.
  • b (int) – The bottom boundary of the clipping area.
  • x1 (int) – The x-coordinate of the starting point of the line.
  • y1 (int) – The y-coordinate of the starting point of the line.
  • x2 (int) – The x-coordinate of the end point of the line.
  • y2 (int) – The y-coordinate of the end point of the line.
  • method (str, optional) – The method to use for clipping lines, can be either ‘cohensutherland’ or ‘liangbarsky’. Defaults to liangbarsky.
Returns:

The start and end coordinates of the clipped line in the form (cx1, cy1, cx2, cy2). If the line does not intersect with the rectangular clipping area, all 4 values will be None.
Return type:

tuple
sdl2.ext.algorithms.point_on_line(p1, p2, point)[source]

Checks if a point falls along a given line segment.

Parameters:
  • p1 (tuple) – The (x, y) coordinates of the starting point of the line.
  • p2 (tuple) – The (x, y) coordinates of the end point of the line.
  • point (tuple) – The (x, y) coordinates to test against the line.
Returns:

True if the point falls along the line segment, otherwise False.
Return type:

bool