[gegl] transform-core: finish top 2 bottom, left 2 right for transform_generic

[Nicolas Robidoux <nrobidoux src gnome org>]

commit bd85a46b8cb05a1be955068940d2722d9dc3846a
Author: Nicolas Robidoux <nrobidoux git gnome org>
Date:   Wed Dec 12 15:40:22 2012 -0500

    transform-core: finish top 2 bottom, left 2 right for transform_generic

 operations/transform/transform-core.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/operations/transform/transform-core.c b/operations/transform/transform-core.c
index 31d2ce7..dd94b3c 100644
--- a/operations/transform/transform-core.c
+++ b/operations/transform/transform-core.c
@@ -1062,6 +1062,8 @@ transform_generic (GeglBuffer  *dest,
        * Compute the positions of the pre-images of the top left and
        * bottom left pixels of the ROI.
        */
+      dest_ptr = dest_buf;
+
       u_start = inverse.coeff [0][0] * (roi->x + (gdouble) 0.5) +
 	        inverse.coeff [0][1] * (roi->y + (gdouble) 0.5) +
                 inverse.coeff [0][2];
@@ -1085,11 +1087,12 @@ transform_generic (GeglBuffer  *dest,
 	  /*
 	   * Move the start to the previously last scanline.
 	   */
+          dest_ptr += (gint) 4 * (roi->height - (gint) 1) * roi->width;
 	  u_start = u_float;
 	  v_start = v_float;
 	  w_start = w_float;
-	}
-  
+	}       
+
       /*
        * Repeat in the horizontal direction, using the first scanline
        * selected by the vertical flip.
@@ -1105,12 +1108,13 @@ transform_generic (GeglBuffer  *dest,
 	   * Move the start to the previously last pixel of the
 	   * scanline.
 	   */
+          dest_ptr += (gint) 4 * (roi->width  - (gint) 1);
 	  u_start = u_float;
 	  v_start = v_float;
 	  w_start = w_float;
 	}
 
-      for (dest_ptr = dest_buf, y = roi->height; y--;)
+      for (y = roi->height; y--;)
         {
           u_float = u_start;
           v_float = v_start;
@@ -1119,6 +1123,7 @@ transform_generic (GeglBuffer  *dest,
           for (x = roi->width; x--;)
             {
               GeglMatrix2 inverse_jacobian;
+
               gdouble w_recip = 1.0 / w_float;
               gdouble u = u_float * w_recip;
               gdouble v = v_float * w_recip;
@@ -1139,13 +1144,15 @@ transform_generic (GeglBuffer  *dest,
                                 dest_ptr,
                                 GEGL_ABYSS_NONE);
 
-              dest_ptr += 4;
+              dest_ptr += flip_x * (gint) 4;
 
               u_float += flip_x * inverse.coeff [0][0];
               v_float += flip_x * inverse.coeff [1][0];
               w_float += flip_x * inverse.coeff [2][0];
             }
 
+          dest_ptr += (gint) 4 * (flip_y - flip_x) * roi->width;
+
           u_start += flip_y * inverse.coeff [0][1];
           v_start += flip_y * inverse.coeff [1][1];
           w_start += flip_y * inverse.coeff [2][1];