1 files changed, 172 insertions, 0 deletions
diff --git a/libmate-desktop/mate-thumbnail-pixbuf-utils.c b/libmate-desktop/mate-thumbnail-pixbuf-utils.c
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+++ b/libmate-desktop/mate-thumbnail-pixbuf-utils.c
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+/*
+ * mate-thumbnail-pixbuf-utils.c: Utilities for handling pixbufs when thumbnailing
+ *
+ * Copyright (C) 2002 Red Hat, Inc.
+ *
+ * This file is part of the Mate Library.
+ *
+ * The Mate 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 Mate 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 Mate Library; see the file COPYING.LIB. If not,
+ * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Author: Alexander Larsson <[email protected]>
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <glib.h>
+
+#define MATE_DESKTOP_USE_UNSTABLE_API
+#include "libmateui/mate-desktop-thumbnail.h"
+
+#define LOAD_BUFFER_SIZE 65536
+
+/**
+ * mate_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: a scaled pixbuf
+ * 
+ * Since: 2.2
+ **/
+GdkPixbuf *
+mate_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 (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;
+}