Split out pixbuf-to-surface conversion code

It will be needed by both the pixbuf loader and the pixbuf library,
so we need to be able to inline-include it to avoid cyclic dependencies
between the two libs.

3 files changed, 115 insertions, 73 deletions

diff --git a/pig/Makefile.am b/pig/Makefile.am
index 0ea4843..8027355 100644
--- a/pig/Makefile.am
+++ b/pig/Makefile.am
@@ -62,7 +62,8 @@ nodist_libpig_@PIG_MAJORMINOR@include_HEADERS = \
 
 noinst_HEADERS = \
 	pig-loader-private.h \
-	pig-marshal-private.h
+	pig-marshal-private.h \
+	pig-pixbuf-shared-private.h
 
 EXTRA_DIST = \
 	pig-marshal.list \
diff --git a/pig/pig-pixbuf-picture.c b/pig/pig-pixbuf-picture.c
index d00bb76..afa6a95 100644
--- a/pig/pig-pixbuf-picture.c
+++ b/pig/pig-pixbuf-picture.c
@@ -24,6 +24,8 @@
 #include <cairo-gobject.h>
 #include <glib/gi18n.h>
 
+#include "pig-pixbuf-shared-private.h"
+
 struct _PigPixbufPicturePrivate {
   GdkPixbuf *pixbuf;
   cairo_surface_t *surface;
@@ -235,90 +237,22 @@ cairo_surface_t *
 pig_pixbuf_create_surface (const GdkPixbuf *pixbuf)
 {
   gint width, height;
-  guchar *gdk_pixels;
-  int gdk_rowstride, n_channels, cairo_stride;
-  guchar *cairo_pixels;
   cairo_format_t format;
   cairo_surface_t *surface;
-  static const cairo_user_data_key_t key;
-  int j;
 
   g_return_val_if_fail (GDK_IS_PIXBUF (pixbuf), NULL);
 
   width = gdk_pixbuf_get_width (pixbuf);
   height = gdk_pixbuf_get_height (pixbuf);
-  gdk_pixels = gdk_pixbuf_get_pixels (pixbuf);
-  gdk_rowstride = gdk_pixbuf_get_rowstride (pixbuf);
-  n_channels = gdk_pixbuf_get_n_channels (pixbuf);
-  if (n_channels == 3)
+  if (gdk_pixbuf_get_n_channels (pixbuf) == 3)
     format = CAIRO_FORMAT_RGB24;
   else
     format = CAIRO_FORMAT_ARGB32;
 
-  cairo_stride = cairo_format_stride_for_width (format, width);
-  cairo_pixels = g_malloc (height * cairo_stride);
-  surface = cairo_image_surface_create_for_data ((unsigned char *)cairo_pixels,
-                                                 format,
-                                                 width, height, cairo_stride);
-
-  cairo_surface_set_user_data (surface, &key,
-                               cairo_pixels, (cairo_destroy_func_t)g_free);
+  surface = cairo_image_surface_create (format, width, height);
 
-  for (j = height; j; j--)
-    {
-      guchar *p = gdk_pixels;
-      guchar *q = cairo_pixels;
-
-      if (n_channels == 3)
-        {
-          guchar *end = p + 3 * width;
-
-          while (p < end)
-            {
-#if G_BYTE_ORDER == G_LITTLE_ENDIAN
-              q[0] = p[2];
-              q[1] = p[1];
-              q[2] = p[0];
-#else
-              q[1] = p[0];
-              q[2] = p[1];
-              q[3] = p[2];
-#endif
-              p += 3;
-              q += 4;
-            }
-        }
-      else
-        {
-          guchar *end = p + 4 * width;
-          guint t1,t2,t3;
-
-#define MULT(d,c,a,t) G_STMT_START { t = c * a + 0x7f; d = ((t >> 8) + t) >> 8; } G_STMT_END
-
-          while (p < end)
-            {
-#if G_BYTE_ORDER == G_LITTLE_ENDIAN
-              MULT(q[0], p[2], p[3], t1);
-              MULT(q[1], p[1], p[3], t2);
-              MULT(q[2], p[0], p[3], t3);
-              q[3] = p[3];
-#else
-              q[0] = p[3];
-              MULT(q[1], p[0], p[3], t1);
-              MULT(q[2], p[1], p[3], t2);
-              MULT(q[3], p[2], p[3], t3);
-#endif
-
-              p += 4;
-              q += 4;
-            }
-
-#undef MULT
-        }
-
-      gdk_pixels += gdk_rowstride;
-      cairo_pixels += cairo_stride;
-    }
+  _pig_pixbuf_copy_to_surface (surface, pixbuf,
+                               0, 0, width, height);
 
   return surface;
 }
diff --git a/pig/pig-pixbuf-shared-private.h b/pig/pig-pixbuf-shared-private.h
new file mode 100644
index 0000000..6011356
--- /dev/null
+++ b/pig/pig-pixbuf-shared-private.h
@@ -0,0 +1,107 @@
+/* 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__ */