Zhang-Suen thinning algorithm: Difference between revisions

Line 107:

* "Character Recognition Systems: A Guide for Students and Practitioners" By Mohamed Cheriet, Nawwaf Kharma, Cheng-Lin Liu, Ching Suen

=={{header|11l}}==

<lang 11l>V beforeTxt =

‘1100111

1100111

1100110

1111110

0000000’

V smallrc01 =

‘00000000000000000000000000000000

01111111110000000111111110000000

01110001111000001111001111000000

01110000111000001110000111000000

01110001111000001110000000000000

01111111110000001110000000000000

01110111100000001110000111000000

01110011110011101111001111011100

01110001111011100111111110011100

00000000000000000000000000000000’

V rc01 =

‘00000000000000000000000000000000000000000000000000000000000

01111111111111111100000000000000000001111111111111000000000

01111111111111111110000000000000001111111111111111000000000

01111111111111111111000000000000111111111111111111000000000

01111111100000111111100000000001111111111111111111000000000

00011111100000111111100000000011111110000000111111000000000

00011111100000111111100000000111111100000000000000000000000

00011111111111111111000000000111111100000000000000000000000

00011111111111111110000000000111111100000000000000000000000

00011111111111111111000000000111111100000000000000000000000

00011111100000111111100000000111111100000000000000000000000

00011111100000111111100000000011111110000000111111000000000

01111111100000111111100000000001111111111111111111000000000

01111111100000111111101111110000111111111111111111011111100

01111111100000111111101111110000001111111111111111011111100

01111111100000111111101111110000000001111111111111011111100

00000000000000000000000000000000000000000000000000000000000’

F intarray(binstring)

‘Change a 2D matrix of 01 chars into a list of lists of ints’

R binstring.split("\n").map(line -> line.map(ch -> (I ch == ‘1’ {1} E 0)))

F chararray(intmatrix)

‘Change a 2d list of lists of 1/0 ints into lines of 1/0 chars’

R intmatrix.map(row -> row.map(p -> String(p)).join(‘’)).join("\n")

F toTxt(intmatrix)

‘Change a 2d list of lists of 1/0 ints into lines of '#' and '.' chars’

R intmatrix.map(row -> row.map(p -> (I p {‘#’} E ‘.’)).join(‘’)).join("\n")

F neighbours_list(x, y, image)

‘Return 8-neighbours of point p1 of picture, in order’

V i = image

V (x1, y1, x_1, y_1) = (x + 1, y - 1, x - 1, y + 1)

R [i[y1][x], i[y1][x1], i[y][x1], i[y_1][x1], i[y_1][x], i[y_1][x_1], i[y][x_1], i[y1][x_1]]

F neighbours_tuple(x, y, image)

‘Return 8-neighbours of point p1 of picture, in order’

V i = image

V (x1, y1, x_1, y_1) = (x + 1, y - 1, x - 1, y + 1)

R (i[y1][x], i[y1][x1], i[y][x1], i[y_1][x1], i[y_1][x], i[y_1][x_1], i[y][x_1], i[y1][x_1])

F transitions(neighbours)

V s = 0

L(i) 7

s += Int((neighbours[i], neighbours[i + 1]) == (0, 1))

R s + Int((neighbours[7], neighbours[0]) == (0, 1))

F zhangSuen(&image)

V changing1 = [(-1, -1)]

V changing2 = [(-1, -1)]

L !changing1.empty | !changing2.empty

changing1.drop()

L(y) 1 .< image.len - 1

L(x) 1 .< image[0].len - 1

V n = neighbours_list(x, y, image)

V (P2, P3, P4, P5, P6, P7, P8, P9) = neighbours_tuple(x, y, image)

I (image[y][x] == 1 & P4 * P6 * P8 == 0 & P2 * P4 * P6 == 0 & transitions(n) == 1 & sum(n) C 2..6)

changing1.append((x, y))

L(x, y) changing1

image[y][x] = 0

changing2.drop()

L(y) 1 .< image.len - 1

L(x) 1 .< image[0].len - 1

V n = neighbours_list(x, y, image)

V (P2, P3, P4, P5, P6, P7, P8, P9) = neighbours_tuple(x, y, image)

I (image[y][x] == 1 & P2 * P6 * P8 == 0 & P2 * P4 * P8 == 0 & transitions(n) == 1 & sum(n) C 2..6)

changing2.append((x, y))

L(x, y) changing2

image[y][x] = 0

R image

L(picture) (beforeTxt, smallrc01, rc01)

V image = intarray(picture)

print("\nFrom:\n#.".format(toTxt(image)))

V after = zhangSuen(&image)

print("\nTo thinned:\n#.".format(toTxt(after)))</lang>

Just the example asked for in the task:

<pre>

From:

...........................................................

.#################...................#############.........

.##################...............################.........

.###################............##################.........

.########.....#######..........###################.........

...######.....#######.........#######.......######.........

...######.....#######........#######.......................

...#################.........#######.......................

...################..........#######.......................

...#################.........#######.......................

...######.....#######........#######.......................

...######.....#######.........#######.......######.........

.########.....#######..........###################.........

.########.....#######.######....##################.######..

.########.....#######.######......################.######..

.########.....#######.######.........#############.######..

...........................................................

To thinned:

...........................................................

....#.##########.......................#######.............

.....##........#...................####.......#............

.....#..........#.................##.......................

.....#..........#................#.........................

.....############...............#..........................

.....#..........#...............#..........................

.....#..........#................#.........................

.....#............................##.......................

.....#.............................############............

.......................###..........................###....

...........................................................

</pre>

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