bresenhams algorithm

def bresenham(x1, y1, x2, y2):
    """
    Bresenham's line algorithm - returns a list of all pixels in a line
    https://en.wikipedia.org/wiki/Bresenham's_line_algorithm
    """
    dx = abs(x2 - x1)
    dy = abs(y2 - y1)
    steep = dy > dx

    if steep:
        x1, y1 = y1, x1
        x2, y2 = y2, x2

    if x1 > x2:
        x1, x2 = x2, x1
        y1, y2 = y2, y1

    dx = abs(x2 - x1)
    dy = abs(y2 - y1)

    offset = 0
    threshold = dx

    y = y1
    for x in range(x1, x2):
        if steep:
            points.append((y, x))
        else:
            points.append((x, y))

        offset += dy