Revert the inverted coordinate system fix. 3D Boxes and guides

require an XML-level backwards compatibility mechanism to fix properly,
and it's too late in the 0.48 cycle to introduce it.

(bzr r9298)

2 files changed, 19 insertions, 4 deletions

diff --git a/src/helper/pixbuf-ops.cpp b/src/helper/pixbuf-ops.cpp
index c26d55b8b..3be63aa68 100644
--- a/src/helper/pixbuf-ops.cpp
+++ b/src/helper/pixbuf-ops.cpp
@@ -113,7 +113,7 @@ sp_generate_internal_bitmap(SPDocument *doc, gchar const */*filename*/,
      double padding = 1.0;
 
      Geom::Point origin(screen.min()[Geom::X],
-                        screen.min()[Geom::Y]);
+                      sp_document_height(doc) - screen[Geom::Y].extent() - screen.min()[Geom::Y]);
 
      origin[Geom::X] = origin[Geom::X] + (screen[Geom::X].extent() * ((1 - padding) / 2));
      origin[Geom::Y] = origin[Geom::Y] + (screen[Geom::Y].extent() * ((1 - padding) / 2));
diff --git a/src/helper/png-write.cpp b/src/helper/png-write.cpp
index 8eb9e27bf..b1c135db0 100644
--- a/src/helper/png-write.cpp
+++ b/src/helper/png-write.cpp
@@ -424,9 +424,24 @@ sp_export_png_file(SPDocument *doc, gchar const *filename,
 
     sp_document_ensure_up_to_date(doc);
 
-    /* Calculate translation */
-    Geom::Point translation = Geom::Point(-area[Geom::X][0], -area[Geom::Y][0]);
-
+    /* Calculate translation by transforming to document coordinates (flipping Y)*/
+    Geom::Point translation = Geom::Point(-area[Geom::X][0], area[Geom::Y][1] - sp_document_height(doc));
+
+    /*  This calculation is only valid when assumed that (x0,y0)= area.corner(0) and (x1,y1) = area.corner(2)
+     * 1) a[0] * x0 + a[2] * y1 + a[4] = 0.0
+     * 2) a[1] * x0 + a[3] * y1 + a[5] = 0.0
+     * 3) a[0] * x1 + a[2] * y1 + a[4] = width
+     * 4) a[1] * x0 + a[3] * y0 + a[5] = height
+     * 5) a[1] = 0.0;
+     * 6) a[2] = 0.0;
+     *
+     * (1,3) a[0] * x1 - a[0] * x0 = width
+     * a[0] = width / (x1 - x0)
+     * (2,4) a[3] * y0 - a[3] * y1 = height
+     * a[3] = height / (y0 - y1)
+     * (1) a[4] = -a[0] * x0
+     * (2) a[5] = -a[3] * y1
+     */
 
     Geom::Matrix const affine(Geom::Translate(translation)
                             * Geom::Scale(width / area.width(),