mask.c

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/*
 * qrencode - QR Code encoder
 *
 * Masking.
 * Copyright (C) 2006-2017 Kentaro Fukuchi <kentaro@fukuchi.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>

#include "qrencode.h"
#include "qrspec.h"
#include "mask.h"

STATIC_IN_RELEASE int Mask_writeFormatInformation(int width, unsigned char *frame, int mask, QRecLevel level)
{
    unsigned int format;
    unsigned char v;
    int i;
    int blacks = 0;

    format = QRspec_getFormatInfo(mask, level);

    for(i = 0; i < 8; i++) {
        if(format & 1) {
            blacks += 2;
            v = 0x85;
        } else {
            v = 0x84;
        }
        frame[width * 8 + width - 1 - i] = v;
        if(i < 6) {
            frame[width * i + 8] = v;
        } else {
            frame[width * (i + 1) + 8] = v;
        }
        format= format >> 1;
    }
    for(i = 0; i < 7; i++) {
        if(format & 1) {
            blacks += 2;
            v = 0x85;
        } else {
            v = 0x84;
        }
        frame[width * (width - 7 + i) + 8] = v;
        if(i == 0) {
            frame[width * 8 + 7] = v;
        } else {
            frame[width * 8 + 6 - i] = v;
        }
        format= format >> 1;
    }

    return blacks;
}

#define N1 (3)
#define N2 (3)
#define N3 (40)
#define N4 (10)

#define MASKMAKER(__exp__) \
    int x, y;\
    int b = 0;\
\
    for(y = 0; y < width; y++) {\
        for(x = 0; x < width; x++) {\
            if(*s & 0x80) {\
                *d = *s;\
            } else {\
                *d = *s ^ ((__exp__) == 0);\
            }\
            b += (int)(*d & 1);\
            s++; d++;\
        }\
    }\
    return b;

static int Mask_mask0(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER((x+y)&1)
}

static int Mask_mask1(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER(y&1)
}

static int Mask_mask2(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER(x%3)
}

static int Mask_mask3(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER((x+y)%3)
}

static int Mask_mask4(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER(((y/2)+(x/3))&1)
}

static int Mask_mask5(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER(((x*y)&1)+(x*y)%3)
}

static int Mask_mask6(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER((((x*y)&1)+(x*y)%3)&1)
}

static int Mask_mask7(int width, const unsigned char *s, unsigned char *d)
{
    MASKMAKER((((x*y)%3)+((x+y)&1))&1)
}

#define maskNum (8)
typedef int MaskMaker(int, const unsigned char *, unsigned char *);
static MaskMaker *maskMakers[maskNum] = {
    Mask_mask0, Mask_mask1, Mask_mask2, Mask_mask3,
    Mask_mask4, Mask_mask5, Mask_mask6, Mask_mask7
};

#ifdef WITH_TESTS
unsigned char *Mask_makeMaskedFrame(int width, unsigned char *frame, int mask)
{
    unsigned char *masked;

    masked = (unsigned char *)malloc((size_t)(width * width));
    if(masked == NULL) return NULL;

    maskMakers[mask](width, frame, masked);

    return masked;
}
#endif

unsigned char *Mask_makeMask(int width, unsigned char *frame, int mask, QRecLevel level)
{
    unsigned char *masked;

    if(mask < 0 || mask >= maskNum) {
        errno = EINVAL;
        return NULL;
    }

    masked = (unsigned char *)malloc((size_t)(width * width));
    if(masked == NULL) return NULL;

    maskMakers[mask](width, frame, masked);
    Mask_writeFormatInformation(width, masked, mask, level);

    return masked;
}


//static int n1;
//static int n2;
//static int n3;
//static int n4;

STATIC_IN_RELEASE int Mask_calcN1N3(int length, int *runLength)
{
    int i;
    int demerit = 0;
    int fact;

    for(i = 0; i < length; i++) {
        if(runLength[i] >= 5) {
            demerit += N1 + (runLength[i] - 5);
            //n1 += N1 + (runLength[i] - 5);
        }
        if((i & 1)) {
            if(i >= 3 && i < length-2 && (runLength[i] % 3) == 0) {
                fact = runLength[i] / 3;
                if(runLength[i-2] == fact &&
                   runLength[i-1] == fact &&
                   runLength[i+1] == fact &&
                   runLength[i+2] == fact) {
                    if(i == 3 || runLength[i-3] >= 4 * fact) {
                        demerit += N3;
                        //n3 += N3;
                    } else if(i+4 >= length || runLength[i+3] >= 4 * fact) {
                        demerit += N3;
                        //n3 += N3;
                    }
                }
            }
        }
    }

    return demerit;
}

STATIC_IN_RELEASE int Mask_calcN2(int width, unsigned char *frame)
{
    int x, y;
    unsigned char *p;
    unsigned char b22, w22;
    int demerit = 0;

    p = frame + width + 1;
    for(y = 1; y < width; y++) {
        for(x = 1; x < width; x++) {
            b22 = p[0] & p[-1] & p[-width] & p [-width-1];
            w22 = p[0] | p[-1] | p[-width] | p [-width-1];
            if((b22 | (w22 ^ 1))&1) {
                demerit += N2;
            }
            p++;
        }
        p++;
    }

    return demerit;
}

STATIC_IN_RELEASE int Mask_calcRunLengthH(int width, unsigned char *frame, int *runLength)
{
    int head;
    int i;
    unsigned char prev;

    if(frame[0] & 1) {
        runLength[0] = -1;
        head = 1;
    } else {
        head = 0;
    }
    runLength[head] = 1;
    prev = frame[0];

    for(i = 1; i < width; i++) {
        if((frame[i] ^ prev) & 1) {
            head++;
            runLength[head] = 1;
            prev = frame[i];
        } else {
            runLength[head]++;
        }
    }

    return head + 1;
}

STATIC_IN_RELEASE int Mask_calcRunLengthV(int width, unsigned char *frame, int *runLength)
{
    int head;
    int i;
    unsigned char prev;

    if(frame[0] & 1) {
        runLength[0] = -1;
        head = 1;
    } else {
        head = 0;
    }
    runLength[head] = 1;
    prev = frame[0];

    for(i = 1; i < width; i++) {
        if((frame[i * width] ^ prev) & 1) {
            head++;
            runLength[head] = 1;
            prev = frame[i * width];
        } else {
            runLength[head]++;
        }
    }

    return head + 1;
}

STATIC_IN_RELEASE int Mask_evaluateSymbol(int width, unsigned char *frame)
{
    int x, y;
    int demerit = 0;
    int runLength[QRSPEC_WIDTH_MAX + 1];
    int length;

    demerit += Mask_calcN2(width, frame);

    for(y = 0; y < width; y++) {
        length = Mask_calcRunLengthH(width, frame + y * width, runLength);
        demerit += Mask_calcN1N3(length, runLength);
    }

    for(x = 0; x < width; x++) {
        length = Mask_calcRunLengthV(width, frame + x, runLength);
        demerit += Mask_calcN1N3(length, runLength);
    }

    return demerit;
}

unsigned char *Mask_mask(int width, unsigned char *frame, QRecLevel level)
{
    int i;
    unsigned char *mask, *bestMask;
    int minDemerit = INT_MAX;
    int blacks;
    int bratio;
    int demerit;
    int w2 = width * width;

    mask = (unsigned char *)malloc((size_t)w2);
    if(mask == NULL) return NULL;
    bestMask = (unsigned char *)malloc((size_t)w2);
    if(bestMask == NULL) {
        free(mask);
        return NULL;
    }

    for(i = 0; i < maskNum; i++) {
//        n1 = n2 = n3 = n4 = 0;
        demerit = 0;
        blacks = maskMakers[i](width, frame, mask);
        blacks += Mask_writeFormatInformation(width, mask, i, level);
        bratio = (200 * blacks + w2) / w2 / 2; /* (int)(100*blacks/w2+0.5) */
        demerit = (abs(bratio - 50) / 5) * N4;
//        n4 = demerit;
        demerit += Mask_evaluateSymbol(width, mask);
//        printf("(%d,%d,%d,%d)=%d\n", n1, n2, n3 ,n4, demerit);
        if(demerit < minDemerit) {
            minDemerit = demerit;
            memcpy(bestMask, mask, (size_t)w2);
        }
    }
    free(mask);
    return bestMask;
}