/*====================================================================*

 -  Copyright (C) 2001 Leptonica.  All rights reserved.

 -

 -  Redistribution and use in source and binary forms, with or without

 -  modification, are permitted provided that the following conditions

 -  are met:

 -  1. Redistributions of source code must retain the above copyright

 -     notice, this list of conditions and the following disclaimer.

 -  2. Redistributions in binary form must reproduce the above

 -     copyright notice, this list of conditions and the following

 -     disclaimer in the documentation and/or other materials

 -     provided with the distribution.

 -

 -  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 -  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 -  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 -  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ANY

 -  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 -  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 -  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 -  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

 -  OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 -  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 -  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *====================================================================*/

/*!

 * \file sel2.c

 * <pre>

 *

 *      Contains definitions of simple structuring elements

 *

 *      Basic brick structuring elements

 *          SELA    *selaAddBasic()

 *               Linear horizontal and vertical

 *               Square

 *               Diagonals

 *

 *      Simple hit-miss structuring elements

 *          SELA    *selaAddHitMiss()

 *               Isolated foreground pixel

 *               Horizontal and vertical edges

 *               Slanted edge

 *               Corners

 *

 *      Structuring elements for comparing with DWA operations

 *          SELA    *selaAddDwaLinear()

 *          SELA    *selaAddDwaCombs()

 *

 *      Structuring elements for the intersection of lines

 *          SELA    *selaAddCrossJunctions()

 *          SELA    *selaAddTJunctions()

 *

 *      Structuring elements for connectivity-preserving thinning operations

 *          SELA    *sela4ccThin()

 *          SELA    *sela8ccThin()

 *          SELA    *sela4and8ccThin()

 *

 *      Other structuring elements

 *          SEL    *selMakePlusSign()

 * </pre>

 */

#ifdef HAVE_CONFIG_H

#include <config_auto.h>

#endif  /* HAVE_CONFIG_H */

#include <math.h>

#include "allheaders.h"

#define L_BUF_SIZE 512

    /* Linear brick sel sizes, including all those that are required

     * for decomposable sels up to size 63. */

static const l_int32  num_linear = 25;

static const l_int32  basic_linear[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11,

       12, 13, 14, 15, 20, 21, 25, 30, 31, 35, 40, 41, 45, 50, 51};

/* ------------------------------------------------------------------- *

 *                    Basic brick structuring elements                 *

 * ------------------------------------------------------------------- */

/*!

 * \brief   selaAddBasic()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds the following sels:

 *            ~ all linear (horiz, vert) brick sels that are

 *              necessary for decomposable sels up to size 63

 *            ~ square brick sels up to size 10

 *            ~ 4 diagonal sels

 * </pre>

 */

SELA *

selaAddBasic(SELA  *sela)

{

char     name[L_BUF_SIZE];

l_int32  i, size;

SEL     *sel;

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

    /*--------------------------------------------------------------*

     *             Linear horizontal and vertical sels              *

     *--------------------------------------------------------------*/

    for (i = 0; i < num_linear; i++) {

        size = basic_linear[i];

        sel = selCreateBrick(1, size, 0, size / 2, 1);

        snprintf(name, L_BUF_SIZE, "sel_%dh", size);

        selaAddSel(sela, sel, name, 0);

    }

    for (i = 0; i < num_linear; i++) {

        size = basic_linear[i];

        sel = selCreateBrick(size, 1, size / 2, 0, 1);

        snprintf(name, L_BUF_SIZE, "sel_%dv", size);

        selaAddSel(sela, sel, name, 0);

    }

    /*-----------------------------------------------------------*

     *                      2-d Bricks                           *

     *-----------------------------------------------------------*/

    for (i = 2; i <= 5; i++) {

        sel = selCreateBrick(i, i, i / 2, i / 2, 1);

        snprintf(name, L_BUF_SIZE, "sel_%d", i);

        selaAddSel(sela, sel, name, 0);

    }

    /*-----------------------------------------------------------*

     *                        Diagonals                          *

     *-----------------------------------------------------------*/

        /*  0c  1

            1   0  */

    sel = selCreateBrick(2, 2, 0, 0, 1);

    selSetElement(sel, 0, 0, 0);

    selSetElement(sel, 1, 1, 0);

    selaAddSel(sela, sel, "sel_2dp", 0);

        /*  1c  0

            0   1   */

    sel = selCreateBrick(2, 2, 0, 0, 1);

    selSetElement(sel, 0, 1, 0);

    selSetElement(sel, 1, 0, 0);

    selaAddSel(sela, sel, "sel_2dm", 0);

        /*  Diagonal, slope +, size 5 */

    sel = selCreate(5, 5, "sel_5dp");

    selSetOrigin(sel, 2, 2);

    selSetElement(sel, 0, 4, 1);

    selSetElement(sel, 1, 3, 1);

    selSetElement(sel, 2, 2, 1);

    selSetElement(sel, 3, 1, 1);

    selSetElement(sel, 4, 0, 1);

    selaAddSel(sela, sel, "sel_5dp", 0);

        /*  Diagonal, slope -, size 5 */

    sel = selCreate(5, 5, "sel_5dm");

    selSetOrigin(sel, 2, 2);

    selSetElement(sel, 0, 0, 1);

    selSetElement(sel, 1, 1, 1);

    selSetElement(sel, 2, 2, 1);

    selSetElement(sel, 3, 3, 1);

    selSetElement(sel, 4, 4, 1);

    selaAddSel(sela, sel, "sel_5dm", 0);

    return sela;

}

/* ------------------------------------------------------------------- *

 *                 Simple hit-miss structuring elements                *

 * ------------------------------------------------------------------- */

/*!

 * \brief   selaAddHitMiss()

 *

 * \param[in]    sela  [optional]

 * \return  sela with additional sels, or NULL on error

 */

SELA *

selaAddHitMiss(SELA  *sela)

{

SEL  *sel;

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

#if 0   /*  use just for testing */

    sel = selCreateBrick(3, 3, 1, 1, 2);

    selaAddSel(sela, sel, "sel_bad", 0);

#endif

    /*--------------------------------------------------------------*

     *                   Isolated foreground pixel                  *

     *--------------------------------------------------------------*/

    sel = selCreateBrick(3, 3, 1, 1, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_HIT);

    selaAddSel(sela, sel, "sel_3hm", 0);

    /*--------------------------------------------------------------*

     *                Horizontal and vertical edges                 *

     *--------------------------------------------------------------*/

    sel = selCreateBrick(2, 3, 0, 1, SEL_HIT);

    selSetElement(sel, 1, 0, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_MISS);

    selSetElement(sel, 1, 2, SEL_MISS);

    selaAddSel(sela, sel, "sel_3de", 0);

    sel = selCreateBrick(2, 3, 1, 1, SEL_HIT);

    selSetElement(sel, 0, 0, SEL_MISS);

    selSetElement(sel, 0, 1, SEL_MISS);

    selSetElement(sel, 0, 2, SEL_MISS);

    selaAddSel(sela, sel, "sel_3ue", 0);

    sel = selCreateBrick(3, 2, 1, 0, SEL_HIT);

    selSetElement(sel, 0, 1, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_MISS);

    selSetElement(sel, 2, 1, SEL_MISS);

    selaAddSel(sela, sel, "sel_3re", 0);

    sel = selCreateBrick(3, 2, 1, 1, SEL_HIT);

    selSetElement(sel, 0, 0, SEL_MISS);

    selSetElement(sel, 1, 0, SEL_MISS);

    selSetElement(sel, 2, 0, SEL_MISS);

    selaAddSel(sela, sel, "sel_3le", 0);

    /*--------------------------------------------------------------*

     *                        Slanted edge                          *

     *--------------------------------------------------------------*/

    sel = selCreateBrick(13, 6, 6, 2, SEL_DONT_CARE);

    selSetElement(sel, 0, 3, SEL_MISS);

    selSetElement(sel, 0, 5, SEL_HIT);

    selSetElement(sel, 4, 2, SEL_MISS);

    selSetElement(sel, 4, 4, SEL_HIT);

    selSetElement(sel, 8, 1, SEL_MISS);

    selSetElement(sel, 8, 3, SEL_HIT);

    selSetElement(sel, 12, 0, SEL_MISS);

    selSetElement(sel, 12, 2, SEL_HIT);

    selaAddSel(sela, sel, "sel_sl1", 0);

    /*--------------------------------------------------------------*

     *                           Corners                            *

     *  This allows for up to 3 missing edge pixels at the corner   *

     *--------------------------------------------------------------*/

    sel = selCreateBrick(4, 4, 1, 1, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_DONT_CARE);

    selSetElement(sel, 1, 2, SEL_DONT_CARE);

    selSetElement(sel, 2, 1, SEL_DONT_CARE);

    selSetElement(sel, 1, 3, SEL_HIT);

    selSetElement(sel, 2, 2, SEL_HIT);

    selSetElement(sel, 2, 3, SEL_HIT);

    selSetElement(sel, 3, 1, SEL_HIT);

    selSetElement(sel, 3, 2, SEL_HIT);

    selSetElement(sel, 3, 3, SEL_HIT);

    selaAddSel(sela, sel, "sel_ulc", 0);

    sel = selCreateBrick(4, 4, 1, 2, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_DONT_CARE);

    selSetElement(sel, 1, 2, SEL_DONT_CARE);

    selSetElement(sel, 2, 2, SEL_DONT_CARE);

    selSetElement(sel, 1, 0, SEL_HIT);

    selSetElement(sel, 2, 0, SEL_HIT);

    selSetElement(sel, 2, 1, SEL_HIT);

    selSetElement(sel, 3, 0, SEL_HIT);

    selSetElement(sel, 3, 1, SEL_HIT);

    selSetElement(sel, 3, 2, SEL_HIT);

    selaAddSel(sela, sel, "sel_urc", 0);

    sel = selCreateBrick(4, 4, 2, 1, SEL_MISS);

    selSetElement(sel, 1, 1, SEL_DONT_CARE);

    selSetElement(sel, 2, 1, SEL_DONT_CARE);

    selSetElement(sel, 2, 2, SEL_DONT_CARE);

    selSetElement(sel, 0, 1, SEL_HIT);

    selSetElement(sel, 0, 2, SEL_HIT);

    selSetElement(sel, 0, 3, SEL_HIT);

    selSetElement(sel, 1, 2, SEL_HIT);

    selSetElement(sel, 1, 3, SEL_HIT);

    selSetElement(sel, 2, 3, SEL_HIT);

    selaAddSel(sela, sel, "sel_llc", 0);

    sel = selCreateBrick(4, 4, 2, 2, SEL_MISS);

    selSetElement(sel, 1, 2, SEL_DONT_CARE);

    selSetElement(sel, 2, 1, SEL_DONT_CARE);

    selSetElement(sel, 2, 2, SEL_DONT_CARE);

    selSetElement(sel, 0, 0, SEL_HIT);

    selSetElement(sel, 0, 1, SEL_HIT);

    selSetElement(sel, 0, 2, SEL_HIT);

    selSetElement(sel, 1, 0, SEL_HIT);

    selSetElement(sel, 1, 1, SEL_HIT);

    selSetElement(sel, 2, 0, SEL_HIT);

    selaAddSel(sela, sel, "sel_lrc", 0);

    return sela;

}

/* ------------------------------------------------------------------- *

 *        Structuring elements for comparing with DWA operations       *

 * ------------------------------------------------------------------- */

/*!

 * \brief   selaAddDwaLinear()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds all linear (horizontal, vertical) sels from

 *          2 to 63 pixels in length, which are the sizes over

 *          which dwa code can be generated.

 * </pre>

 */

SELA *

selaAddDwaLinear(SELA  *sela)

{

char     name[L_BUF_SIZE];

l_int32  i;

SEL     *sel;

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

    for (i = 2; i < 64; i++) {

        sel = selCreateBrick(1, i, 0, i / 2, 1);

        snprintf(name, L_BUF_SIZE, "sel_%dh", i);

        selaAddSel(sela, sel, name, 0);

    }

    for (i = 2; i < 64; i++) {

        sel = selCreateBrick(i, 1, i / 2, 0, 1);

        snprintf(name, L_BUF_SIZE, "sel_%dv", i);

        selaAddSel(sela, sel, name, 0);

    }

    return sela;

}

/*!

 * \brief   selaAddDwaCombs()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds all comb (horizontal, vertical) Sels that are

 *          used in composite linear morphological operations

 *          up to 63 pixels in length, which are the sizes over

 *          which dwa code can be generated.

 * </pre>

 */

SELA *

selaAddDwaCombs(SELA  *sela)

{

char     name[L_BUF_SIZE];

l_int32  i, f1, f2, prevsize, size;

SEL     *selh, *selv;

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

    prevsize = 0;

    for (i = 4; i < 64; i++) {

        selectComposableSizes(i, &f1, &f2);

        size = f1 * f2;

        if (size == prevsize)

            continue;

        selectComposableSels(i, L_HORIZ, NULL, &selh);

        if (selh) {

            snprintf(name, L_BUF_SIZE, "sel_comb_%dh", size);

            selaAddSel(sela, selh, name, 0);

        } else {

            L_ERROR("selh not made for i = %d\n", __func__, i);

        }

        selectComposableSels(i, L_VERT, NULL, &selv);

        if (selv) {

            snprintf(name, L_BUF_SIZE, "sel_comb_%dv", size);

            selaAddSel(sela, selv, name, 0);

        } else {

            L_ERROR("selv not made for i = %d\n", __func__, i);

        }

        prevsize = size;

    }

    return sela;

}

/* ------------------------------------------------------------------- *

 *          Structuring elements for the intersection of lines         *

 * ------------------------------------------------------------------- */

/*!

 * \brief   selaAddCrossJunctions()

 *

 * \param[in]    sela [optional]

 * \param[in]    hlsize length of each line of hits from origin

 * \param[in]    mdist distance of misses from the origin

 * \param[in]    norient number of orientations; max of 8

 * \param[in]    debugflag 1 for debug output

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds hitmiss Sels for the intersection of two lines.

 *          If the lines are very thin, they must be nearly orthogonal

 *          to register.

 *      (2) The number of Sels generated is equal to %norient.

 *      (3) If %norient == 2, this generates 2 Sels of crosses, each with

 *          two perpendicular lines of hits.  One Sel has horizontal and

 *          vertical hits; the other has hits along lines at +-45 degrees.

 *          Likewise, if %norient == 3, this generates 3 Sels of crosses

 *          oriented at 30 degrees with each other.

 *      (4) It is suggested that %hlsize be chosen at least 1 greater

 *          than %mdist.  Try values of (%hlsize, %mdist) such as

 *          (6,5), (7,6), (8,7), (9,7), etc.

 * </pre>

 */

SELA *

selaAddCrossJunctions(SELA      *sela,

                      l_float32  hlsize,

                      l_float32  mdist,

                      l_int32    norient,

                      l_int32    debugflag)

{

char       name[L_BUF_SIZE];

l_int32    i, j, w, xc, yc;

l_float64  pi, halfpi, radincr, radang;

l_float64  angle;

PIX       *pixc, *pixm, *pixt;

PIXA      *pixa;

PTA       *pta1, *pta2, *pta3, *pta4;

SEL       *sel;

    if (hlsize <= 0)

        return (SELA *)ERROR_PTR("hlsize not > 0", __func__, NULL);

    if (norient < 1 || norient > 8)

        return (SELA *)ERROR_PTR("norient not in [1, ... 8]", __func__, NULL);

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

    pi = 3.1415926535;

    halfpi = 3.1415926535 / 2.0;

    radincr = halfpi / (l_float64)norient;

    w = (l_int32)(2.2 * (L_MAX(hlsize, mdist) + 0.5));

    if (w % 2 == 0)

        w++;

    xc = w / 2;

    yc = w / 2;

    pixa = pixaCreate(norient);

    for (i = 0; i < norient; i++) {

            /* Set the don't cares */

        pixc = pixCreate(w, w, 32);

        pixSetAll(pixc);

            /* Add the green lines of hits */

        pixm = pixCreate(w, w, 1);

        radang = (l_float32)i * radincr;

        pta1 = generatePtaLineFromPt(xc, yc, hlsize + 1, radang);

        pta2 = generatePtaLineFromPt(xc, yc, hlsize + 1, radang + halfpi);

        pta3 = generatePtaLineFromPt(xc, yc, hlsize + 1, radang + pi);

        pta4 = generatePtaLineFromPt(xc, yc, hlsize + 1, radang + pi + halfpi);

        ptaJoin(pta1, pta2, 0, -1);

        ptaJoin(pta1, pta3, 0, -1);

        ptaJoin(pta1, pta4, 0, -1);

        pixRenderPta(pixm, pta1, L_SET_PIXELS);

        pixPaintThroughMask(pixc, pixm, 0, 0, 0x00ff0000);

        ptaDestroy(&pta1);

        ptaDestroy(&pta2);

        ptaDestroy(&pta3);

        ptaDestroy(&pta4);

            /* Add red misses between the lines */

        for (j = 0; j < 4; j++) {

            angle = radang + (j - 0.5) * halfpi;

            pixSetPixel(pixc, xc + (l_int32)(mdist * cos(angle)),

                        yc + (l_int32)(mdist * sin(angle)), 0xff000000);

        }

            /* Add dark green for origin */

        pixSetPixel(pixc, xc, yc, 0x00550000);

            /* Generate the sel */

        sel = selCreateFromColorPix(pixc, NULL);

        snprintf(name, sizeof(name), "sel_cross_%d", i);

        selaAddSel(sela, sel, name, 0);

        if (debugflag) {

            pixt = pixScaleBySampling(pixc, 10.0, 10.0);

            pixaAddPix(pixa, pixt, L_INSERT);

        }

        pixDestroy(&pixm);

        pixDestroy(&pixc);

    }

    if (debugflag) {

        l_int32  w;

        lept_mkdir("lept/sel");

        pixaGetPixDimensions(pixa, 0, &w, NULL, NULL);

        pixt = pixaDisplayTiledAndScaled(pixa, 32, w, 1, 0, 10, 2);

        pixWriteDebug("/tmp/lept/sel/xsel1.png", pixt, IFF_PNG);

        pixDisplay(pixt, 0, 100);

        pixDestroy(&pixt);

        pixt = selaDisplayInPix(sela, 15, 2, 20, 1);

        pixWriteDebug("/tmp/lept/sel/xsel2.png", pixt, IFF_PNG);

        pixDisplay(pixt, 500, 100);

        pixDestroy(&pixt);

        selaWriteStream(stderr, sela);

    }

    pixaDestroy(&pixa);

    return sela;

}

/*!

 * \brief   selaAddTJunctions()

 *

 * \param[in]    sela [optional]

 * \param[in]    hlsize length of each line of hits from origin

 * \param[in]    mdist distance of misses from the origin

 * \param[in]    norient number of orientations; max of 8

 * \param[in]    debugflag 1 for debug output

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds hitmiss Sels for the T-junction of two lines.

 *          If the lines are very thin, they must be nearly orthogonal

 *          to register.

 *      (2) The number of Sels generated is 4 * %norient.

 *      (3) It is suggested that %hlsize be chosen at least 1 greater

 *          than %mdist.  Try values of (%hlsize, %mdist) such as

 *          (6,5), (7,6), (8,7), (9,7), etc.

 * </pre>

 */

SELA *

selaAddTJunctions(SELA      *sela,

                  l_float32  hlsize,

                  l_float32  mdist,

                  l_int32    norient,

                  l_int32    debugflag)

{

char       name[L_BUF_SIZE];

l_int32    i, j, k, w, xc, yc;

l_float64  pi, halfpi, radincr, jang, radang;

l_float64  angle[3], dist[3];

PIX       *pixc, *pixm, *pixt;

PIXA      *pixa;

PTA       *pta1, *pta2, *pta3;

SEL       *sel;

    if (hlsize <= 2)

        return (SELA *)ERROR_PTR("hlsizel not > 1", __func__, NULL);

    if (norient < 1 || norient > 8)

        return (SELA *)ERROR_PTR("norient not in [1, ... 8]", __func__, NULL);

    if (!sela) {

        if ((sela = selaCreate(0)) == NULL)

            return (SELA *)ERROR_PTR("sela not made", __func__, NULL);

    }

    pi = 3.1415926535;

    halfpi = 3.1415926535 / 2.0;

    radincr = halfpi / (l_float32)norient;

    w = (l_int32)(2.4 * (L_MAX(hlsize, mdist) + 0.5));

    if (w % 2 == 0)

        w++;

    xc = w / 2;

    yc = w / 2;

    pixa = pixaCreate(4 * norient);

    for (i = 0; i < norient; i++) {

        for (j = 0; j < 4; j++) {  /* 4 orthogonal orientations */

            jang = (l_float32)j * halfpi;

                /* Set the don't cares */

            pixc = pixCreate(w, w, 32);

            pixSetAll(pixc);

                /* Add the green lines of hits */

            pixm = pixCreate(w, w, 1);

            radang = (l_float32)i * radincr;

            pta1 = generatePtaLineFromPt(xc, yc, hlsize + 1, jang + radang);

            pta2 = generatePtaLineFromPt(xc, yc, hlsize + 1,

                                         jang + radang + halfpi);

            pta3 = generatePtaLineFromPt(xc, yc, hlsize + 1,

                                         jang + radang + pi);

            ptaJoin(pta1, pta2, 0, -1);

            ptaJoin(pta1, pta3, 0, -1);

            pixRenderPta(pixm, pta1, L_SET_PIXELS);

            pixPaintThroughMask(pixc, pixm, 0, 0, 0x00ff0000);

            ptaDestroy(&pta1);

            ptaDestroy(&pta2);

            ptaDestroy(&pta3);

                /* Add red misses between the lines */

            angle[0] = radang + jang - halfpi;

            angle[1] = radang + jang + 0.5 * halfpi;

            angle[2] = radang + jang + 1.5 * halfpi;

            dist[0] = 0.8 * mdist;

            dist[1] = dist[2] = mdist;

            for (k = 0; k < 3; k++) {

                pixSetPixel(pixc, xc + (l_int32)(dist[k] * cos(angle[k])),

                            yc + (l_int32)(dist[k] * sin(angle[k])),

                            0xff000000);

            }

                /* Add dark green for origin */

            pixSetPixel(pixc, xc, yc, 0x00550000);

                /* Generate the sel */

            sel = selCreateFromColorPix(pixc, NULL);

            snprintf(name, sizeof(name), "sel_cross_%d", 4 * i + j);

            selaAddSel(sela, sel, name, 0);

            if (debugflag) {

                pixt = pixScaleBySampling(pixc, 10.0, 10.0);

                pixaAddPix(pixa, pixt, L_INSERT);

            }

            pixDestroy(&pixm);

            pixDestroy(&pixc);

        }

    }

    if (debugflag) {

        l_int32  w;

        lept_mkdir("lept/sel");

        pixaGetPixDimensions(pixa, 0, &w, NULL, NULL);

        pixt = pixaDisplayTiledAndScaled(pixa, 32, w, 4, 0, 10, 2);

        pixWriteDebug("/tmp/lept/sel/tsel1.png", pixt, IFF_PNG);

        pixDisplay(pixt, 0, 100);

        pixDestroy(&pixt);

        pixt = selaDisplayInPix(sela, 15, 2, 20, 4);

        pixWriteDebug("/tmp/lept/sel/tsel2.png", pixt, IFF_PNG);

        pixDisplay(pixt, 500, 100);

        pixDestroy(&pixt);

        selaWriteStream(stderr, sela);

    }

    pixaDestroy(&pixa);

    return sela;

}

/* -------------------------------------------------------------------------- *

 *    Structuring elements for connectivity-preserving thinning operations    *

 * -------------------------------------------------------------------------- */

    /* ------------------------------------------------------------

     * These sels (and their rotated counterparts) are the useful

     * 3x3 Sels for thinning.   The notation is based on

     * "Connectivity-preserving morphological image transformations,"

     * a version of which can be found at

     *           http://www.leptonica.com/papers/conn.pdf

     * ------------------------------------------------------------ */

    /* Sels for 4-connected thinning */

static const char *sel_4_1 = "  x"

                             "oCx"

                             "  x";

static const char *sel_4_2 = "  x"

                             "oCx"

                             " o ";

static const char *sel_4_3 = " o "

                             "oCx"

                             "  x";

static const char *sel_4_4 = " o "

                             "oCx"

                             " o ";

static const char *sel_4_5 = " ox"

                             "oCx"

                             " o ";

static const char *sel_4_6 = " o "

                             "oCx"

                             " ox";

static const char *sel_4_7 = " xx"

                             "oCx"

                             " o ";

static const char *sel_4_8 = "  x"

                             "oCx"

                             "o x";

static const char *sel_4_9 = "o x"

                             "oCx"

                             "  x";

    /* Sels for 8-connected thinning */

static const char *sel_8_1 = " x "

                             "oCx"

                             " x ";

static const char *sel_8_2 = " x "

                             "oCx"

                             "o  ";

static const char *sel_8_3 = "o  "

                             "oCx"

                             " x ";

static const char *sel_8_4 = "o  "

                             "oCx"

                             "o  ";

static const char *sel_8_5 = "o x"

                             "oCx"

                             "o  ";

static const char *sel_8_6 = "o  "

                             "oCx"

                             "o x";

static const char *sel_8_7 = " x "

                             "oCx"

                             "oo ";

static const char *sel_8_8 = " x "

                             "oCx"

                             "ox ";

static const char *sel_8_9 = "ox "

                             "oCx"

                             " x ";

    /* Sels for both 4 and 8-connected thinning */

static const char *sel_48_1 = " xx"

                              "oCx"

                              "oo ";

static const char *sel_48_2 = "o x"

                              "oCx"

                              "o x";

/*!

 * \brief   sela4ccThin()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds the 9 basic sels for 4-cc thinning.

 * </pre>

 */

SELA *

sela4ccThin(SELA  *sela)

{

SEL  *sel;

    if (!sela) sela = selaCreate(9);

    sel = selCreateFromString(sel_4_1, 3, 3, "sel_4_1");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_2, 3, 3, "sel_4_2");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_3, 3, 3, "sel_4_3");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_4, 3, 3, "sel_4_4");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_5, 3, 3, "sel_4_5");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_6, 3, 3, "sel_4_6");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_7, 3, 3, "sel_4_7");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_8, 3, 3, "sel_4_8");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_4_9, 3, 3, "sel_4_9");

    selaAddSel(sela, sel, NULL, 0);

    return sela;

}

/*!

 * \brief   sela8ccThin()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds the 9 basic sels for 8-cc thinning.

 * </pre>

 */

SELA *

sela8ccThin(SELA  *sela)

{

SEL  *sel;

    if (!sela) sela = selaCreate(9);

    sel = selCreateFromString(sel_8_1, 3, 3, "sel_8_1");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_2, 3, 3, "sel_8_2");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_3, 3, 3, "sel_8_3");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_4, 3, 3, "sel_8_4");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_5, 3, 3, "sel_8_5");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_6, 3, 3, "sel_8_6");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_7, 3, 3, "sel_8_7");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_8, 3, 3, "sel_8_8");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_8_9, 3, 3, "sel_8_9");

    selaAddSel(sela, sel, NULL, 0);

    return sela;

}

/*!

 * \brief   sela4and8ccThin()

 *

 * \param[in]    sela [optional]

 * \return  sela with additional sels, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Adds the 2 basic sels for either 4-cc or 8-cc thinning.

 * </pre>

 */

SELA *

sela4and8ccThin(SELA  *sela)

{

SEL  *sel;

    if (!sela) sela = selaCreate(2);

    sel = selCreateFromString(sel_48_1, 3, 3, "sel_48_1");

    selaAddSel(sela, sel, NULL, 0);

    sel = selCreateFromString(sel_48_2, 3, 3, "sel_48_2");

    selaAddSel(sela, sel, NULL, 0);

    return sela;

}

/* -------------------------------------------------------------------------- *

 *                        Other structuring elements                          *

 * -------------------------------------------------------------------------- */

/*!

 * \brief   selMakePlusSign()

 *

 * \param[in]    size        side of containing square

 * \param[in]    linewidth   of lines

 * \return  sel, or NULL on error

 *

 * <pre>

 * Notes:

 *      (1) Useful for debugging to show location of selected pixels.

 *      (2) See displaySelectedPixels() for an example of use.

 * </pre>

 */

SEL *

selMakePlusSign(l_int32  size,

                l_int32  linewidth)

{

PIX  *pix;

SEL  *sel;

    if (size < 3 || linewidth > size)

        return (SEL *)ERROR_PTR("invalid input", __func__, NULL);

    pix = pixCreate(size, size, 1);

    pixRenderLine(pix, size / 2, 0, size / 2, size - 1,

                  linewidth, L_SET_PIXELS);

    pixRenderLine(pix, 0, size / 2, size, size / 2,

                  linewidth, L_SET_PIXELS);

    sel = selCreateFromPix(pix, size / 2, size / 2, "plus_sign");

    pixDestroy(&pix);

    return sel;

}