/*
 * io-png.c: GdkPixBuf I/O for PNG files.
 * Copyright (C) 1999 Mark Crichton
 * Author: Mark Crichton <crichton@gimp.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Cambridge, MA 02139, USA.
 *
 */
#include <config.h>
#include <stdio.h>
#include <glib.h>
#include "gdk-pixbuf.h"
#include "gdk-pixbuf-io.h"
#include <png.h>

/* Shared library entry point */
GdkPixBuf *image_load(FILE * f)
{
    png_structp png_ptr;
    png_infop info_ptr, end_info;
    gint i, depth, ctype, inttype, passes, bpp;		/* bpp = BYTES/pixel */
    png_uint_32 w, h, x, y;
    png_bytepp rows;
    art_u8 *pixels, *temp, *rowdata;
    GdkPixBuf *pixbuf;

    g_return_val_if_fail(f != NULL, NULL);

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL,
				     NULL);

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
	png_destroy_read_struct(&png_ptr, NULL, NULL);
	return NULL;
    }
    end_info = png_create_info_struct(png_ptr);
    if (!end_info) {
	png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
	return NULL;
    }
    if (setjmp(png_ptr->jmpbuf)) {
	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
	return NULL;
    }
    png_init_io(png_ptr, f);
    png_read_info(png_ptr, info_ptr);

    png_get_IHDR(png_ptr, info_ptr, &w, &h, &depth, &ctype, &inttype,
		 NULL, NULL);

    /* Ok, we want to work with 24 bit images.
     * However, PNG can vary depth per channel.
     * So, we use the png_set_expand function to expand
     * everything into a format libart expects.
     * We also use png_set_strip_16 to reduce down to 8 bit/chan.
     */

    if (ctype == PNG_COLOR_TYPE_PALETTE && depth <= 8)
	png_set_expand(png_ptr);

    if (ctype == PNG_COLOR_TYPE_GRAY && depth < 8)
	png_set_expand(png_ptr);

    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
	png_set_expand(png_ptr);

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

    /* We also have png "packing" bits into bytes if < 8 */
    if (depth < 8)
	png_set_packing(png_ptr);

    /* Lastly, if the PNG is greyscale, convert to RGB */
    if (ctype == PNG_COLOR_TYPE_GRAY || ctype == PNG_COLOR_TYPE_GRAY_ALPHA)
	png_set_gray_to_rgb(png_ptr);

    /* ...and if we're interlaced... */
    passes = png_set_interlace_handling(png_ptr);

    /* Update our info structs */
    png_read_update_info(png_ptr, info_ptr);

    /* Allocate some memory and set up row array */
    /* This "inhales vigirously"... */
    if (ctype & PNG_COLOR_MASK_ALPHA)
	bpp = 4;
    else
	bpp = 3;

    pixels = art_alloc(w * h * bpp);
    rows = g_malloc(h * sizeof(png_bytep));

    if ((!pixels) || (!rows)) {
	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
	return NULL;
    }
    /* Icky code, but it has to be done... */
    for (i = 0; i < h; i++) {
	if ((rows[i] = g_malloc(w * sizeof(art_u8) * bpp)) == NULL) {
	    int n;
	    for (n = 0; n < i; n++)
		g_free(rows[i]);
	    g_free(rows);
	    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
	    return NULL;
	}
    }

    /* And we FINALLY get here... */
    png_read_image(png_ptr, rows);
    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);

    /* Now stuff the bytes into pixels & free rows[y] */

    temp = pixels;

    for (y = 0; y < h; y++) {
	(png_bytep) rowdata = rows[y];
	for (x = 0; x < w; x++) {
	    temp[0] = rowdata[(x * bpp)];
	    temp[1] = rowdata[(x * bpp) + 1];
	    temp[2] = rowdata[(x * bpp) + 2];
	    if (bpp == 4)
		temp[3] = rowdata[(x * bpp) + 3];
	    temp += bpp;
	}
	g_free(rows[y]);
    }
    g_free(rows);

    /* Return the GdkPixBuf */
    pixbuf = g_new(GdkPixBuf, 1);

    if (ctype & PNG_COLOR_MASK_ALPHA)
	pixbuf->art_pixbuf = art_pixbuf_new_rgba(pixels, w, h, (w * 4));
    else
	pixbuf->art_pixbuf = art_pixbuf_new_rgb(pixels, w, h, (w * 3));

    /* Ok, I'm anal...shoot me */
    if (!(pixbuf->art_pixbuf))
	return NULL;
    pixbuf->ref_count = 0;
    pixbuf->unref_func = NULL;

    return pixbuf;
}