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/*
* gnome-thumbnail-pixbuf-utils.c: Utilities for handling pixbufs when thumbnailing
*
* Copyright (C) 2002 Red Hat, Inc.
*
* This file is part of the Gnome Library.
*
* The Gnome 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.
*
* The Gnome 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 the Gnome Library; see the file COPYING.LIB. If not,
* write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
* Author: Alexander Larsson <alexl@redhat.com>
*/
#include <config.h>
#include <stdlib.h>
#include <string.h>
#include <glib.h>
#define GNOME_DESKTOP_USE_UNSTABLE_API
#include "gnome-desktop-thumbnail.h"
#define LOAD_BUFFER_SIZE 65536
/**
* gnome_desktop_thumbnail_scale_down_pixbuf:
* @pixbuf: a #GdkPixbuf
* @dest_width: the desired new width
* @dest_height: the desired new height
*
* Scales the pixbuf to the desired size. This function
* is a lot faster than gdk-pixbuf when scaling down by
* large amounts.
*
* Return value: (transfer full): a scaled pixbuf
*
* Since: 2.2
**/
GdkPixbuf *
gnome_desktop_thumbnail_scale_down_pixbuf (GdkPixbuf *pixbuf,
int dest_width,
int dest_height)
{
int source_width, source_height;
int s_x1, s_y1, s_x2, s_y2;
int s_xfrac, s_yfrac;
int dx, dx_frac, dy, dy_frac;
div_t ddx, ddy;
int x, y;
int r, g, b, a;
int n_pixels;
gboolean has_alpha;
guchar *dest, *src, *xsrc, *src_pixels;
GdkPixbuf *dest_pixbuf;
int pixel_stride;
int source_rowstride, dest_rowstride;
if (dest_width == 0 || dest_height == 0) {
return NULL;
}
source_width = gdk_pixbuf_get_width (pixbuf);
source_height = gdk_pixbuf_get_height (pixbuf);
g_assert (source_width >= dest_width);
g_assert (source_height >= dest_height);
ddx = div (source_width, dest_width);
dx = ddx.quot;
dx_frac = ddx.rem;
ddy = div (source_height, dest_height);
dy = ddy.quot;
dy_frac = ddy.rem;
has_alpha = gdk_pixbuf_get_has_alpha (pixbuf);
source_rowstride = gdk_pixbuf_get_rowstride (pixbuf);
src_pixels = gdk_pixbuf_get_pixels (pixbuf);
dest_pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, has_alpha, 8,
dest_width, dest_height);
dest = gdk_pixbuf_get_pixels (dest_pixbuf);
dest_rowstride = gdk_pixbuf_get_rowstride (dest_pixbuf);
pixel_stride = (has_alpha)?4:3;
s_y1 = 0;
s_yfrac = -dest_height/2;
while (s_y1 < source_height) {
s_y2 = s_y1 + dy;
s_yfrac += dy_frac;
if (s_yfrac > 0) {
s_y2++;
s_yfrac -= dest_height;
}
s_x1 = 0;
s_xfrac = -dest_width/2;
while (s_x1 < source_width) {
s_x2 = s_x1 + dx;
s_xfrac += dx_frac;
if (s_xfrac > 0) {
s_x2++;
s_xfrac -= dest_width;
}
/* Average block of [x1,x2[ x [y1,y2[ and store in dest */
r = g = b = a = 0;
n_pixels = 0;
src = src_pixels + s_y1 * source_rowstride + s_x1 * pixel_stride;
for (y = s_y1; y < s_y2; y++) {
xsrc = src;
if (has_alpha) {
for (x = 0; x < s_x2-s_x1; x++) {
n_pixels++;
r += xsrc[3] * xsrc[0];
g += xsrc[3] * xsrc[1];
b += xsrc[3] * xsrc[2];
a += xsrc[3];
xsrc += 4;
}
} else {
for (x = 0; x < s_x2-s_x1; x++) {
n_pixels++;
r += *xsrc++;
g += *xsrc++;
b += *xsrc++;
}
}
src += source_rowstride;
}
if (n_pixels != 0) /* avoid any possible divide by zero */
{
if (has_alpha) {
if (a != 0) {
*dest++ = r / a;
*dest++ = g / a;
*dest++ = b / a;
*dest++ = a / n_pixels;
} else {
*dest++ = 0;
*dest++ = 0;
*dest++ = 0;
*dest++ = 0;
}
} else {
*dest++ = r / n_pixels;
*dest++ = g / n_pixels;
*dest++ = b / n_pixels;
}
}
s_x1 = s_x2;
}
s_y1 = s_y2;
dest += dest_rowstride - dest_width * pixel_stride;
}
return dest_pixbuf;
}
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