lib/ccv_swt.c

ccv_swt

void ccv_swt(ccv_dense_matrix_t *a, ccv_dense_matrix_t **b, int type, ccv_swt_param_t params)

Compute the Stroke-Width-Transform image.

• a: The input matrix.
• b: The output matrix.
• type: The type of the output matrix, if 0, ccv will default to CCV_32S | CCV_C1.
• params: A ccv_swt_param_t structure that defines various aspect of the SWT function.

ccv_swt_param_t

Canny parameters

• high_thresh: Parameters for Canny edge detector.
• low_thresh: Parameters for Canny edge detector.
• size: Parameters for Canny edge detector.

Geometry filtering parameters

• aspect_ratio: The maximum aspect ratio for a letter.
• max_height: The maximum height for a letter.
• min_area: The minimum occupied area for a letter.
• min_height: The minimum height for a letter.
• std_ratio: The inner-class standard derivation when grouping letters.

Grouping parameters

• distance_ratio: The allowable distance variance when grouping letters.
• elongate_ratio: The allowable elongate variance when grouping letters.
• height_ratio: The allowable height variance when grouping letters.
• intensity_thresh: The allowable intensity variance when grouping letters.
• intersect_ratio: The allowable intersect variance when grouping letters.
• letter_thresh: The allowable letter threshold.
• thickness_ratio: The allowable thickness variance when grouping letters.

Break textline into words

• breakdown: If breakdown text line into words.
• breakdown_ratio: Apply OSTU and if inter-class variance above the threshold, it will be break down into words.
• direction: SWT direction. (black to white or white to black).
• interval: Intervals for scale invariant option.
• min_neighbors: Minimal neighbors to make a detection valid, this is for scale-invariant version.
• same_word_thresh: Overlapping more than 0.1 of the bigger one (0), and 0.9 of the smaller one (1)
• scale_invariant: Enable scale invariant swt (to scale to different sizes and then combine the results)

ccv_swt_detect_words

ccv_swt_detect_words(ccv_dense_matrix_t *a, ccv_swt_param_t params)

Return array of regions that are potentially text area.

• a: The input matrix.
• params: A ccv_swt_param_t structure that defines various aspect of the SWT function.

return: A ccv_array_t of ccv_comp_t with detection results.

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