zint/backend/png.c

/* png.c - Handles output to PNG file */
/*
    libzint - the open source barcode library
    Copyright (C) 2009-2026 Robin Stuart <rstuart114@gmail.com>

    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.
    3. Neither the name of the project nor the names of its contributors
       may be used to endorse or promote products derived from this software
       without specific prior written permission.

    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 THE COPYRIGHT OWNER OR 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.
 */
/* SPDX-License-Identifier: BSD-3-Clause */

#ifndef ZINT_NO_PNG

#include <assert.h>
#include <errno.h>
#include <math.h>
#include <stdio.h>
#include <png.h>
#include <zlib.h>
#include <setjmp.h>
#include "common.h"
#include "filemem.h"
#include "output.h"

/* Note using "zpng_" prefix not "png_" to avoid clashing with libpng */

/* Note if change this need to change "backend/tests/test_png.c" definition also */
struct zpng_error_type {
    struct zint_symbol *symbol;
    jmp_buf jmpbuf;
};

/* Passed to `png_create_write_struct()` as `error_fn` */
static void zpng_error_handler(png_structp png_ptr, png_const_charp msg) {
    struct zpng_error_type *error_ptr = (struct zpng_error_type *) png_get_error_ptr(png_ptr);
    assert(error_ptr);
    z_errtxtf(0, error_ptr->symbol, 635, "libpng error: %s", msg ? msg : "<NULL>");
    longjmp(error_ptr->jmpbuf, 1);
}

#ifdef ZINT_TEST /* Wrapper for direct testing */
INTERNAL void zint_test_zpng_error_handler(png_structp png_ptr, png_const_charp msg) {
    zpng_error_handler(png_ptr, msg);
}
#endif

/* libpng write callback */
static void zpng_write(png_structp png_ptr, png_bytep ptr, size_t size) {
    struct filemem *fmp = (struct filemem *) png_get_io_ptr(png_ptr);
    (void) zint_fm_write(ptr, 1, size, fmp);
}

/* libpng flush callback */
static void zpng_flush(png_structp png_ptr) {
    struct filemem *fmp = (struct filemem *) png_get_io_ptr(png_ptr);
    (void) zint_fm_flush(fmp);
}

/* Guesstimate best compression strategy */
static int zpng_guess_compression_strategy(struct zint_symbol *symbol, const unsigned char *pixelbuf) {
    (void)pixelbuf;

    /* TODO: Do properly */

    /* It seems the best choice for typical barcode pngs is one of Z_DEFAULT_STRATEGY and Z_FILTERED */

    /* Some guesses */
    if (symbol->symbology == BARCODE_MAXICODE) {
        return Z_DEFAULT_STRATEGY;
    }
    if (symbol->symbology == BARCODE_AZTEC && symbol->bitmap_width <= 30) {
        return Z_DEFAULT_STRATEGY;
    }

    /* Z_FILTERED seems to work better for slightly more barcodes+data so default to that */
    return Z_FILTERED;
}

INTERNAL int zint_png_pixel_plot(struct zint_symbol *symbol, const unsigned char *pixelbuf) {
    struct zpng_error_type zpng_error; /* Passed to `png_create_write_struct()` as `error_ptr` */
    struct filemem fm;
    struct filemem *const fmp = &fm;
    png_structp png_ptr;
    png_infop info_ptr;
    int i;
    int row, column;
    png_color bg, fg;
    unsigned char bg_alpha, fg_alpha;
    unsigned char map[128];
    png_color palette[256];
    int num_palette;
    unsigned char trans_alpha[256];
    int num_trans; /* Note initialize below to avoid gcc -Wclobbered warning due to `longjmp()` */
    int bit_depth;
    int compression_strategy;
    const unsigned char *pb;
    const int grayscale = zint_out_grayscale(symbol);
    unsigned char *outdata = (unsigned char *) z_alloca(symbol->bitmap_width);

    zpng_error.symbol = symbol;

    (void) zint_out_colour_get_rgb(symbol->fgcolour, &fg.red, &fg.green, &fg.blue, &fg_alpha);
    (void) zint_out_colour_get_rgb(symbol->bgcolour, &bg.red, &bg.green, &bg.blue, &bg_alpha);

    num_trans = 0;
    if (symbol->symbology == BARCODE_ULTRA) {
        static const unsigned char ultra_chars[8] = { 'W', 'C', 'B', 'M', 'R', 'Y', 'G', 'K' };
        for (i = 0; i < 8; i++) {
            map[ultra_chars[i]] = i;
            zint_out_colour_char_to_rgb(ultra_chars[i], &palette[i].red, &palette[i].green, &palette[i].blue);
            if (fg_alpha != 0xff) {
                trans_alpha[i] = fg_alpha;
            }
        }
        num_palette = 8;
        if (fg_alpha != 0xff) {
            num_trans = 8;
        }

        /* For Ultracode, have foreground only if have bind/box */
        if (symbol->border_width > 0 && (symbol->output_options & (BARCODE_BIND | BARCODE_BOX | BARCODE_BIND_TOP))) {
            /* Check whether can re-use black */
            if (fg.red == 0 && fg.green == 0 && fg.blue == 0) {
                map['1'] = 7; /* Re-use black */
            } else {
                map['1'] = num_palette;
                palette[num_palette++] = fg;
                if (fg_alpha != 0xff) {
                    trans_alpha[num_trans++] = fg_alpha;
                }
            }
        }

        /* For Ultracode, have background only if have whitespace/quiet zones */
        if (symbol->whitespace_width > 0 || symbol->whitespace_height > 0
                || ((symbol->output_options & BARCODE_QUIET_ZONES)
                    && !(symbol->output_options & BARCODE_NO_QUIET_ZONES))) {
            /* Check whether can re-use white */
            if (bg.red == 0xff && bg.green == 0xff && bg.blue == 0xff && bg_alpha == fg_alpha) {
                map['0'] = 0; /* Re-use white */
            } else {
                if (bg_alpha == 0xff || fg_alpha != 0xff) {
                    /* No alpha or have foreground alpha - add to end */
                    map['0'] = num_palette;
                    palette[num_palette++] = bg;
                } else {
                    /* Alpha and no foreground alpha - add to front & move white to end */
                    png_color white = palette[0]; /* Take copy */
                    map['0'] = 0;
                    palette[0] = bg;
                    map['W'] = num_palette;
                    palette[num_palette++] = white;
                }
                if (bg_alpha != 0xff) {
                    trans_alpha[num_trans++] = bg_alpha;
                }
            }
        }
    } else if (grayscale) {
        const int diff_red = fg.red - bg.red;
        const int diff_green = fg.green - bg.green;
        const int diff_blue = fg.blue - bg.blue;
        for (num_palette = 0; num_palette <= 0xFF; num_palette++) {
            png_color color;
            color.red = bg.red + (diff_red * num_palette) / 0xFF;
            color.green = bg.green + (diff_green * num_palette) / 0xFF;
            color.blue = bg.blue + (diff_blue * num_palette) / 0xFF;
            palette[num_palette] = color;
        }
        if (bg_alpha != 0xFF || fg_alpha != 0xFF) {
            trans_alpha[num_trans++] = bg_alpha;
            if (fg_alpha != 0xFF) {
                for (; num_trans <= 0xFF; num_trans++) {
                    trans_alpha[num_trans] = fg_alpha;
                }
            }
        }
    } else {
        int bg_idx = 0, fg_idx = 1;
        /* Do alphas first so can swop indexes if background not alpha */
        if (bg_alpha != 0xff) {
            trans_alpha[num_trans++] = bg_alpha;
        }
        if (fg_alpha != 0xff) {
            trans_alpha[num_trans++] = fg_alpha;
            if (num_trans == 1) {
                /* Only foreground has alpha so swop indexes - saves a byte! */
                bg_idx = 1;
                fg_idx = 0;
            }
        }

        map['0'] = bg_idx;
        palette[bg_idx] = bg;
        map['1'] = fg_idx;
        palette[fg_idx] = fg;
        num_palette = 2;
    }

    if (num_palette <= 2) {
        bit_depth = 1;
    } else if (num_palette <= 16) {
        bit_depth = 4;
    } else {
        bit_depth = 8;
    }

    /* Open output file in binary mode */
    if (!zint_fm_open(fmp, symbol, "wb")) {
        return ZEXT z_errtxtf(ZINT_ERROR_FILE_ACCESS, symbol, 632, "Could not open PNG output file (%1$d: %2$s)",
                                fmp->err, strerror(fmp->err));
    }

    /* Set up error handling routine as proc() above */
    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, &zpng_error, zpng_error_handler, NULL);
    if (!png_ptr) {
        (void) zint_fm_close(fmp, symbol);
        return z_errtxt(ZINT_ERROR_MEMORY, symbol, 633, "Insufficient memory for PNG write structure buffer");
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_write_struct(&png_ptr, NULL);
        (void) zint_fm_close(fmp, symbol);
        return z_errtxt(ZINT_ERROR_MEMORY, symbol, 634, "Insufficient memory for PNG info structure buffer");
    }

    /* catch jumping here */
    if (setjmp(zpng_error.jmpbuf)) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
        (void) zint_fm_close(fmp, symbol);
        return ZINT_ERROR_MEMORY;
    }

    /* Set our output functions */
    png_set_write_fn(png_ptr, fmp, zpng_write, zpng_flush);

    /* set compression */
    png_set_compression_level(png_ptr, 9);

    /* Compression strategy can make a difference */
    compression_strategy = zpng_guess_compression_strategy(symbol, pixelbuf);
    if (compression_strategy != Z_DEFAULT_STRATEGY) {
        png_set_compression_strategy(png_ptr, compression_strategy);
    }

    if (symbol->dpmm) {
        int resolution = (int) roundf(z_stripf(symbol->dpmm * 1000.0f)); /* pixels per metre */
        png_set_pHYs(png_ptr, info_ptr, resolution, resolution, PNG_RESOLUTION_METER);
    }

    /* set Header block */
    png_set_IHDR(png_ptr, info_ptr, symbol->bitmap_width, symbol->bitmap_height,
            bit_depth, PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
            PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

    png_set_PLTE(png_ptr, info_ptr, palette, num_palette);
    if (num_trans) {
        png_set_tRNS(png_ptr, info_ptr, trans_alpha, num_trans, NULL);
    }

    /* write all chunks up to (but not including) first IDAT */
    png_write_info(png_ptr, info_ptr);

    /* Pixel Plotting */
    pb = pixelbuf;
    if (bit_depth == 1) {
        for (row = 0; row < symbol->bitmap_height; row++) {
            if (row && memcmp(pb, pb - symbol->bitmap_width, symbol->bitmap_width) == 0) {
                pb += symbol->bitmap_width;
            } else {
                unsigned char *image_data = outdata;
                for (column = 0; column < symbol->bitmap_width; column += 8, image_data++) {
                    unsigned char byte = 0;
                    for (i = 0; i < 8 && column + i < symbol->bitmap_width; i++, pb++) {
                        byte |= map[*pb] << (7 - i);
                    }
                    *image_data = byte;
                }
            }
            /* write row contents to file */
            png_write_row(png_ptr, outdata);
        }
    } else if (bit_depth == 4) {
        for (row = 0; row < symbol->bitmap_height; row++) {
            if (row && memcmp(pb, pb - symbol->bitmap_width, symbol->bitmap_width) == 0) {
                pb += symbol->bitmap_width;
            } else {
                unsigned char *image_data = outdata;
                for (column = 0; column < symbol->bitmap_width; column += 2, image_data++) {
                    unsigned char byte = map[*pb++] << 4;
                    if (column + 1 < symbol->bitmap_width) {
                        byte |= map[*pb++];
                    }
                    *image_data = byte;
                }
            }
            /* write row contents to file */
            png_write_row(png_ptr, outdata);

#ifdef ZINT_TEST
            if (symbol->debug & 4096) { /* ZINT_DEBUG_TEST_PNG_FLUSH */
                png_write_flush(png_ptr);
            }
#endif
        }
    } else { /* Bit depth 8 */
        for (row = 0; row < symbol->bitmap_height; row++) {
            /* write row contents to file */
            png_write_row(png_ptr, pb);
            pb += symbol->bitmap_width;
        }
    }

    /* End the file */
    png_write_end(png_ptr, NULL);

    /* make sure we have disengaged */
    png_destroy_write_struct(&png_ptr, &info_ptr);

    if (zint_fm_error(fmp)) {
        (void) ZEXT z_errtxtf(0, symbol, 638, "Incomplete write of PNG output (%1$d: %2$s)",
                        fmp->err, strerror(fmp->err));
        (void) zint_fm_close(fmp, symbol);
        return ZINT_ERROR_FILE_WRITE;
    }

    if (!zint_fm_close(fmp, symbol)) {
        return ZEXT z_errtxtf(ZINT_ERROR_FILE_WRITE, symbol, 960, "Failure on closing PNG output file (%1$d: %2$s)",
                                fmp->err, strerror(fmp->err));
    }

    return 0;
}
/* vim: set ts=4 sw=4 et : */
#else
#if defined(__clang__)
/* Suppresses clang-tidy-18 "clang-diagnostic-empty-translation-unit" */
typedef int zpng_make_clang_tidy_compilers_happy;
#endif
#endif /* ZINT_NO_PNG */