/*
 * Copyright © 2005 Novell, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without
 * fee, provided that the above copyright notice appear in all copies
 * and that both that copyright notice and this permission notice
 * appear in supporting documentation, and that the name of
 * Novell, Inc. not be used in advertising or publicity pertaining to
 * distribution of the software without specific, written prior permission.
 * Novell, Inc. makes no representations about the suitability of this
 * software for any purpose. It is provided "as is" without express or
 * implied warranty.
 *
 * NOVELL, INC. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
 * NO EVENT SHALL NOVELL, INC. BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
 * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Author: David Reveman <davidr@novell.com>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>
#include <setjmp.h>

#define FALSE 0
#define TRUE (!FALSE)
static void
premultiplyData (png_structp   png,
		 png_row_infop row_info,
		 png_bytep     data)
{
    unsigned int i;

    for (i = 0; i < row_info->rowbytes; i += 4)
    {
	unsigned char *base = &data[i];
	unsigned char blue  = base[0];
	unsigned char green = base[1];
	unsigned char red   = base[2];
	unsigned char alpha = base[3];
	int	      p;

	red   = (unsigned) red   * (unsigned) alpha / 255;
	green = (unsigned) green * (unsigned) alpha / 255;
	blue  = (unsigned) blue  * (unsigned) alpha / 255;

	p = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
	memcpy (base, &p, sizeof (int));
    }
}

int readPng(const char   *filename,
            char	      **data,
            unsigned int *width,
            unsigned int *height)
{
    static const int PNG_SIG_SIZE = 8;
    unsigned char    png_sig[PNG_SIG_SIZE];
    FILE	     *file;
    int		     sig_bytes;
    png_struct	     *png;
    png_info	     *info;
    png_uint_32	     png_width, png_height;
    int	     depth, color_type, interlace, i;
    unsigned int     pixel_size;
    png_byte	     **row_pointers;

    file = fopen (filename, "r");
    if (!file)
    {
        fprintf(stderr, "Couldn't open file: '%s'\n", filename);
        return FALSE;
    }

    sig_bytes = fread (png_sig, 1, PNG_SIG_SIZE, file);
    if (png_check_sig (png_sig, sig_bytes) == 0)
    {
	fclose (file);
	return FALSE;
    }

    png = png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
    if (!png)
    {
	fclose (file);
	return FALSE;
    }

    info = png_create_info_struct (png);
    if (info == NULL)
    {
	fclose (file);
	png_destroy_read_struct (&png, NULL, NULL);
	return FALSE;
    }

    png_init_io (png, file);
    png_set_sig_bytes (png, sig_bytes);

    png_read_info (png, info);

    png_get_IHDR (png, info,
		  &png_width, &png_height, &depth,
		  &color_type, &interlace, NULL, NULL);
    *width = png_width;
    *height = png_height;

    /* convert palette/gray image to rgb */
    if (color_type == PNG_COLOR_TYPE_PALETTE)
	png_set_palette_to_rgb (png);

    /* expand gray bit depth if needed */
    if (color_type == PNG_COLOR_TYPE_GRAY && depth < 8)
	png_set_expand_gray_1_2_4_to_8 (png);

    /* transform transparency to alpha */
    if (png_get_valid(png, info, PNG_INFO_tRNS))
	png_set_tRNS_to_alpha (png);

    if (depth == 16)
	png_set_strip_16 (png);

    if (depth < 8)
	png_set_packing (png);

    /* convert grayscale to RGB */
    if (color_type == PNG_COLOR_TYPE_GRAY ||
	color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
	png_set_gray_to_rgb (png);

    if (interlace != PNG_INTERLACE_NONE)
	png_set_interlace_handling (png);

    png_set_bgr (png);
    png_set_filler (png, 0xff, PNG_FILLER_AFTER);

    png_set_read_user_transform_fn (png, premultiplyData);

    png_read_update_info (png, info);

    pixel_size = 4;
    *data = (char *) malloc (png_width * png_height * pixel_size);
    if (*data == NULL)
    {
	fclose (file);
	return FALSE;
    }

    row_pointers = (png_byte **) malloc (png_height * sizeof (char *));
    for (i=0; i < png_height; i++)
	row_pointers[i] = (png_byte *) (*data + i * png_width * pixel_size);

    png_read_image (png, row_pointers);
    png_read_end (png, info);

    free (row_pointers);
    fclose (file);

    png_destroy_read_struct (&png, &info, NULL);

    return TRUE;
}