/* Pig
 * Copyright (C) 2011 Benjamin Otte <otte@gnome.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 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
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifndef __PIG_PIXBUF_SHARED_PRIVATE_H__
#define __PIG_PIXBUF_SHARED_PRIVATE_H__

#include <pig/pig.h>

#include <gdk-pixbuf/gdk-pixbuf.h>

/* This header contains code as inline functions that is used by both
 * libpig-pixbuf and libpig (in particular: The pixbuf loader).
 */

G_BEGIN_DECLS

static inline guint8
_pig_multiply_alpha (guint8 color,
                     guint8 alpha)
{
  guint temp = (alpha * color) + 0x80;
  return (temp + (temp >> 8)) >> 8;
}

static inline void
_pig_pixbuf_copy_to_surface (cairo_surface_t *surface,
                             const GdkPixbuf *pixbuf,
                             int              x,
                             int              y,
                             int              width,
                             int              height)
{
  guchar *gdk_pixels, *cairo_pixels;
  int gdk_stride, n_channels, cairo_stride;
  int i, j;

  /* spell out the invariants that must hold for this code to work */
  g_assert (cairo_image_surface_get_format (surface) == CAIRO_FORMAT_ARGB32 || cairo_image_surface_get_format (surface) == CAIRO_FORMAT_RGB24);
  g_assert (cairo_image_surface_get_width (surface) == gdk_pixbuf_get_width (pixbuf));
  g_assert (cairo_image_surface_get_height (surface) == gdk_pixbuf_get_height (pixbuf));
  g_assert (x >= 0 && y >= 0);
  g_assert (x + width <= cairo_image_surface_get_width (surface));
  g_assert (y + height <= cairo_image_surface_get_height (surface));

  gdk_pixels = gdk_pixbuf_get_pixels (pixbuf);
  gdk_stride = gdk_pixbuf_get_rowstride (pixbuf);
  n_channels = gdk_pixbuf_get_n_channels (pixbuf);
  gdk_pixels += x * n_channels + y * gdk_stride;

  cairo_pixels = cairo_image_surface_get_data (surface);
  cairo_stride = cairo_image_surface_get_stride (surface);
  cairo_pixels += x * 4 + y * cairo_stride;

  for (j = 0; j < height; j++)
    {
      guchar *p = gdk_pixels;
      guint32 *q = (guint32 *) cairo_pixels;

      if (n_channels == 3)
        {
          for (i = 0; i < width; i++)
            {
              q[i] = (0xFF << 24) |
                     (p[0] << 16) |
                     (p[1] << 8 ) |
                      p[2];

              p += 3;
            }
        }
      else
        {
          for (i = 0; i < width; i++)
            {
              q[i] = (p[3]                             << 24) |
                     (_pig_multiply_alpha (p[0], p[3]) << 16) |
                     (_pig_multiply_alpha (p[1], p[3]) <<  8) |
                      _pig_multiply_alpha (p[2], p[3]);

              p += 4;
            }
        }

      gdk_pixels += gdk_stride;
      cairo_pixels += cairo_stride;
    }
}

G_END_DECLS

#endif /* __PIG_PIXBUF_SHARED_PRIVATE_H__ */