binreduce.c

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/*====================================================================*
 -  Copyright (C) 2001 Leptonica.  All rights reserved.
 -  This software is distributed in the hope that it will be
 -  useful, but with NO WARRANTY OF ANY KIND.
 -  No author or distributor accepts responsibility to anyone for the
 -  consequences of using this software, or for whether it serves any
 -  particular purpose or works at all, unless he or she says so in
 -  writing.  Everyone is granted permission to copy, modify and
 -  redistribute this source code, for commercial or non-commercial
 -  purposes, with the following restrictions: (1) the origin of this
 -  source code must not be misrepresented; (2) modified versions must
 -  be plainly marked as such; and (3) this notice may not be removed
 -  or altered from any source or modified source distribution.
 *====================================================================*/

/*
 *  binreduce.c
 *
 *      Subsampled reduction
 *
 *           PIX    *pixReduceBinary2()
 *
 *      Rank filtered reductions
 *
 *           PIX    *pixReduceRankBinaryCascade()
 *           PIX    *pixReduceRankBinary2()
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "allheaders.h"


/*------------------------------------------------------------------*
 *                       Subsampled reduction                       *
 *------------------------------------------------------------------*/
/*!
 *  pixReduceBinary2()
 *
 *      Input:  pixs
 *              tab (<optional>; if null, a table is made here
 *                   and destroyed before exit)
 *      Return: pixd (2x subsampled), or null on error
 */
PIX *
pixReduceBinary2(PIX      *pixs,
                 l_uint8  *intab)
{
l_uint8   *tab;
l_int32    ws, hs, wpls, wpld;
l_uint32  *datas, *datad;
PIX       *pixd;

    PROCNAME("pixReduceBinary2");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);

    if (pixGetDepth(pixs) != 1)
        return (PIX *)ERROR_PTR("pixs not binary", procName, NULL);

    if (intab) /* use input table */
        tab = intab;
    else {
        if ((tab = makeSubsampleTab2x()) == NULL)
            return (PIX *)ERROR_PTR("tab not made", procName, NULL);
    }
    
    ws = pixGetWidth(pixs);
    hs = pixGetHeight(pixs);
    if (hs <= 1)
        return (PIX *)ERROR_PTR("hs must be at least 2", procName, NULL);
    wpls = pixGetWpl(pixs);
    datas = pixGetData(pixs);

    if ((pixd = pixCreate(ws / 2, hs / 2, 1)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    pixCopyResolution(pixd, pixs);
    pixScaleResolution(pixd, 0.5, 0.5);
    wpld = pixGetWpl(pixd);
    datad = pixGetData(pixd);

    reduceBinary2Low(datad, wpld, datas, hs, wpls, tab);

    if (intab == NULL)
        FREE(tab);

    return pixd;
}


/*------------------------------------------------------------------*
 *                   Rank filtered binary reductions                *
 *------------------------------------------------------------------*/
/*!
 *  pixReduceRankBinaryCascade()
 *
 *      Input:  pixs (1 bpp)
 *              level1, ... level 4 (thresholds, in the set {0, 1, 2, 3, 4})
 *      Return: pixd, or null on error
 *
 *  Notes:
 *      (1) This performs up to four cascaded 2x rank reductions.
 *      (2) Use level = 0 to truncate the cascade.
 */
PIX *
pixReduceRankBinaryCascade(PIX     *pixs,
                           l_int32  level1,
                           l_int32  level2,
                           l_int32  level3,
                           l_int32  level4)
{
PIX      *pix1, *pix2, *pix3, *pix4;
l_uint8  *tab;

    PROCNAME("pixReduceRankBinaryCascade");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixGetDepth(pixs) != 1)
        return (PIX *)ERROR_PTR("pixs must be binary", procName, NULL);
    if (level1 > 4 || level2 > 4 || level3 > 4 || level4 > 4)
        return (PIX *)ERROR_PTR("levels must not exceed 4", procName, NULL);

    if (level1 <= 0) {
        L_WARNING("no reduction because level1 not > 0", procName);
        return pixCopy(NULL, pixs);
    }

    if ((tab = makeSubsampleTab2x()) == NULL)
        return (PIX *)ERROR_PTR("tab not made", procName, NULL);
    
    pix1 = pixReduceRankBinary2(pixs, level1, tab);
    if (level2 <= 0) {
        FREE(tab);
        return pix1;
    }

    pix2 = pixReduceRankBinary2(pix1, level2, tab);
    pixDestroy(&pix1);
    if (level3 <= 0) {
        FREE(tab);
        return pix2;
    }

    pix3 = pixReduceRankBinary2(pix2, level3, tab);
    pixDestroy(&pix2);
    if (level4 <= 0) {
        FREE(tab);
        return pix3;
    }

    pix4 = pixReduceRankBinary2(pix3, level4, tab);
    pixDestroy(&pix3);
    FREE(tab);
    return pix4;
}


/*!
 *  pixReduceRankBinary2()
 *
 *      Input:  pixs (1 bpp)
 *              level (rank threshold: 1, 2, 3, 4)
 *              intab (<optional>; if null, a table is made here
 *                     and destroyed before exit)
 *      Return: pixd (1 bpp, 2x rank threshold reduced), or null on error
 *
 *  Notes:
 *      (1) pixd is downscaled by 2x from pixs.
 *      (2) The rank threshold specifies the minimum number of ON
 *          pixels in each 2x2 region of pixs that are required to
 *          set the corresponding pixel ON in pixd.
 */
PIX *
pixReduceRankBinary2(PIX      *pixs,
                     l_int32   level,
                     l_uint8  *intab)
{
l_uint8   *tab;
l_int32    ws, hs, wpls, wpld;
l_uint32  *datas, *datad;
PIX       *pixd;

    PROCNAME("pixReduceRankBinary2");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);

    if (pixGetDepth(pixs) != 1)
        return (PIX *)ERROR_PTR("pixs not binary", procName, NULL);
    if (level < 1 || level > 4)
        return (PIX *)ERROR_PTR("level must be in set {1,2,3,4}",
            procName, NULL);

    if (intab) /* use input table */
        tab = intab;
    else {
        if ((tab = makeSubsampleTab2x()) == NULL)
            return (PIX *)ERROR_PTR("tab not made", procName, NULL);
    }
    
    ws = pixGetWidth(pixs);
    hs = pixGetHeight(pixs);
    if (hs <= 1)
        return (PIX *)ERROR_PTR("hs must be at least 2", procName, NULL);
    wpls = pixGetWpl(pixs);
    datas = pixGetData(pixs);

    if ((pixd = pixCreate(ws / 2, hs / 2, 1)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    pixCopyResolution(pixd, pixs);
    pixScaleResolution(pixd, 0.5, 0.5);
    wpld = pixGetWpl(pixd);
    datad = pixGetData(pixd);

    reduceRankBinary2Low(datad, wpld, datas, hs, wpls, tab, level);

    if (!intab)
        FREE(tab);

    return pixd;
}