swtloc.core.swt_strokes

swtloc.core.swt_strokes(edged_image, hstep_mat, vstep_mat, dstep_mat, max_stroke_width, min_stroke_width, image_height, image_width, check_angle_deviation, image_gradient_theta, max_angle_deviation, include_edges_in_swt)[source]

Core Logic for Stroke Width Transform. Implementing the work of [Boris Epshtein, Eyal Ofek & Yonatan Wexler](https://www.microsoft.com/en-us/research/publication/detecting-text-in-natural-scenes-with-stroke-width-transform/)

Objective of this function is to, given an edged input image, find the stroke widths conforming to the following rules :

  • Each Stroke Width has be in the range of : min_stroke_width<= stroke_widths<=max_stroke_width

  • A ray emanating from each edge point, traveling in its gradients direction, when met with another

edge point will terminate its journey only when the difference between their gradient directional angles is np.pi - max_angle_deviation <= theta_diff <= np.pi + max_angle_deviation

Parameters

  • edged_image (np.ndarray) – Edges of the Original Input Image. Same size as the original image

  • hstep_mat (np.ndarray) – For each pixel, cos(gradient_theta), where gradient_theta is the gradient angle for that pixel, representing length of horizontal movement for every unit movement in gradients direction. Same size as the original image

  • vstep_mat (np.ndarray) – For each pixel, sin(gradient_theta), where gradient_theta is the gradient angle for that pixel, representing length of vertical movement for every unit movement in gradients direction. Same size as the original image

  • dstep_mat (np.ndarray) – np.sqrt(hstep_mat**2+vstep_mat**2)

  • max_stroke_width (int) – Maximum Stroke Width which would be permissible

  • min_stroke_width (int) – Minimum Stroke Width which would be required

  • image_height (int) – Height of the image

  • image_width (int) – Width of the image

  • check_angle_deviation (bool) – Whether to check the angle deviation to terminate the ray

  • image_gradient_theta (np.ndarray) – Gradient array of the input image

  • max_angle_deviation (float) – Maximum Angle Deviation which would be permissible

  • include_edges_in_swt (bool) – Whether to include edges in the final SWT result

Returns

Stroke Width Transformed Image, each stroke filled with stroke length.

Return type

(np.ndarray)