shapes: 2D shapes drawing

This module provides functions making masks on an image.

  • circle_fill() function generates coordinates of a circle in an image.
  • draw_line() function generates coordinates of a line in an image.
  • polygon_fill_mask() function generates a mask from a set of points defining a polygon.

The Polygon class provides checking if a point is inside a polygon.

The whole module uses the (row, col) (i.e., (y, x))) convention for 2D coordinates.

circle_fill(int crow, int ccol, float radius)

Generates coordinate of image points lying in a disk.

Parameters:
  • crow (int) – Row of the center of the disk
  • ccol (int) – Column of the center of the disk
  • radius (float) – Radius of the disk
Returns:

Array coordinates of points inside the disk (might be negative)
Return type:

2-tuple of numpy.ndarray (rows, cols)
ellipse_fill(int crow, int ccol, float radius_r, float radius_c)

Generates coordinate of image points lying in a ellipse.

Parameters:
  • crow (int) – Row of the center of the ellipse
  • ccol (int) – Column of the center of the ellipse
  • radius_r (float) – Radius of the ellipse in the row
  • radius_c (float) – Radius of the ellipse in the column
Returns:

Array coordinates of points inside the ellipse (might be negative)
Return type:

2-tuple of numpy.ndarray (rows, cols)
draw_line(int row0, int col0, int row1, int col1, int width=1)

Line includes both end points. Width is handled by drawing parallel lines, so junctions of lines belonging to different octant with width > 1 will not look nice.

Using Bresenham line algorithm: Bresenham, J. E. Algorithm for computer control of a digital plotter. IBM Systems Journal. Vol 4 No 1. 1965. pp 25-30

Parameters:
  • row0 (int) – Start point row
  • col0 (int) – Start point col
  • row1 (int) – End point row
  • col1 (int) – End point col
  • width (int) – Thickness of the line in pixels (default 1) Width must be at least 1.
Returns:

Array coordinates of points inside the line (might be negative)
Return type:

2-tuple of numpy.ndarray (rows, cols)
polygon_fill_mask(vertices, shape)

Return a mask of boolean, True for pixels inside a polygon.

Parameters:
  • vertices (numpy.ndarray like container of dimension Nx2) – Strip of segments end points (row, column) or (y, x)
  • shape (2-tuple of int) – size of the mask as (height, width)
Returns:

Mask corresponding to the polygon
Return type:

numpy.ndarray of dimension shape
class Polygon(vertices)

Define a polygon that provides inside check and mask generation.

Parameters:vertices (Nx2 array of floats of (row, col)) – corners of the polygon
is_inside(self, row, col)

Check if (row, col) is inside or outside the polygon

Parameters:
  • row (float) –
  • col (float) –
Returns:

True if position is inside polygon, False otherwise
make_mask(self, int height, int width)

Create a mask array representing the filled polygon

Parameters:
  • height (int) – Height of the mask array
  • width (int) – Width of the mask array
Returns:

2D array (height, width)