#include <png.h>
#include <stdio.h>
#include <stdlib.h>
#include <zbar.h>

#if !defined(PNG_LIBPNG_VER) || PNG_LIBPNG_VER < 10018 || \
    (PNG_LIBPNG_VER > 10200 && PNG_LIBPNG_VER < 10209)
/* Changes to Libpng from version 1.2.42 to 1.4.0 (January 4, 2010)
 * ...
 * 2. m. The function png_set_gray_1_2_4_to_8() was removed. It has been
 *       deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
 *       png_set_expand_gray_1_2_4_to_8() because the former function also
 *       expanded palette images.
 */
#define png_set_expand_gray_1_2_4_to_8 png_set_gray_1_2_4_to_8
#endif

zbar_image_scanner_t *scanner = NULL;

/* to complete a runnable example, this abbreviated implementation of
 * get_data() will use libpng to read an image file. refer to libpng
 * documentation for details
 */
static void get_data(const char *name, int *width, int *height, void **raw)
{
    png_structp png;
    png_infop info;
    int color, bits;
    png_bytep *rows;
    int i;
    FILE *file = fopen(name, "rb");

    if (!file)
	exit(2);
    png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png)
	exit(3);
    if (setjmp(png_jmpbuf(png)))
	exit(4);
    info = png_create_info_struct(png);
    if (!info)
	exit(5);
    png_init_io(png, file);
    png_read_info(png, info);
    /* configure for 8bpp grayscale input */
    color = png_get_color_type(png, info);
    bits  = png_get_bit_depth(png, info);
    if (color & PNG_COLOR_TYPE_PALETTE)
	png_set_palette_to_rgb(png);
    if (color == PNG_COLOR_TYPE_GRAY && bits < 8)
	png_set_expand_gray_1_2_4_to_8(png);
    if (bits == 16)
	png_set_strip_16(png);
    if (color & PNG_COLOR_MASK_ALPHA)
	png_set_strip_alpha(png);
    if (color & PNG_COLOR_MASK_COLOR)
	png_set_rgb_to_gray_fixed(png, 1, -1, -1);

    /* allocate image */
    *width  = png_get_image_width(png, info);
    *height = png_get_image_height(png, info);
    *raw    = (png_bytep)calloc(*width * *height, sizeof(png_byte));
    rows    = (png_bytep *)calloc(*height, sizeof(*rows));

    for (i = 0; i < *height; i++)
	rows[i] = ((png_bytep)(*raw)) + (*width * i);

    png_read_image(png, rows);
    free(rows);
}

int main(int argc, char **argv)
{
    int width, height, n;
    void *raw;
    zbar_image_t *image;
    const zbar_symbol_t *symbol;

    if (argc < 2)
	return (1);

    /* create a reader */
    scanner = zbar_image_scanner_create();

    /* configure the reader */
    zbar_image_scanner_set_config(scanner, 0, ZBAR_CFG_ENABLE, 1);

    /* obtain image data */
    width = 0, height = 0;
    raw = NULL;
    get_data(argv[1], &width, &height, &raw);

    /* wrap image data */
    image = zbar_image_create();
    zbar_image_set_format(image, zbar_fourcc('Y', '8', '0', '0'));
    zbar_image_set_size(image, width, height);
    zbar_image_set_data(image, raw, width * height, zbar_image_free_data);

    /* scan the image for barcodes */
    n = zbar_scan_image(scanner, image);

    /* extract results */
    symbol = zbar_image_first_symbol(image);
    for (; symbol; symbol = zbar_symbol_next(symbol)) {
	/* do something useful with results */
	zbar_symbol_type_t typ = zbar_symbol_get_type(symbol);
	const char *data       = zbar_symbol_get_data(symbol);

	printf("decoded %s symbol \"%s\"\n", zbar_get_symbol_name(typ), data);
    }

    /* clean up */
    zbar_image_destroy(image);
    zbar_image_scanner_destroy(scanner);

    return (0);
}