postproc : Added SPLITMV visualization, fix line constrain.

Now draw 16 vectors for SPLITMV mode.

Fixed constrain line to block divide by zero issues.

Blend block was not centering the shaded area correctly.

Change-Id: I1edabd8b4e553aac8d980f7b45c80159e9202434

vp8/common/postproc.c

@@ -484,7 +484,7 @@ void vp8_blend_mb_c (unsigned char *y, unsigned char *u, unsigned char *v,
     int u1_const = u1*((1<<16)-alpha);
     int v1_const = v1*((1<<16)-alpha);
 
-    y += stride + 2;
+    y += stride + 1;
     for (i = 0; i < 14; i++)
     {
         for (j = 0; j < 14; j++)
@@ -522,7 +522,7 @@ static void constrain_line (int x0, int *x1, int y0, int *y1, int width, int hei
         dy = *y1 - y0;
 
         *x1 = width;
-        if (dy)
+        if (dx)
             *y1 = ((width-x0)*dy)/dx + y0;
     }
     if (*x1 < 0)
@@ -531,7 +531,7 @@ static void constrain_line (int x0, int *x1, int y0, int *y1, int width, int hei
         dy = *y1 - y0;
 
         *x1 = 0;
-        if (dy)
+        if (dx)
             *y1 = ((0-x0)*dy)/dx + y0;
     }
     if (*y1 > height)
@@ -540,7 +540,7 @@ static void constrain_line (int x0, int *x1, int y0, int *y1, int width, int hei
         dy = *y1 - y0;
 
         *y1 = height;
-        if (dx)
+        if (dy)
             *x1 = ((height-y0)*dx)/dy + x0;
     }
     if (*y1 < 0)
@@ -549,7 +549,7 @@ static void constrain_line (int x0, int *x1, int y0, int *y1, int width, int hei
         dy = *y1 - y0;
 
         *y1 = 0;
-        if (dx)
+        if (dy)
             *x1 = ((0-y0)*dx)/dy + x0;
     }
 }
@@ -753,8 +753,36 @@ int vp8_post_proc_frame(VP8_COMMON *oci, YV12_BUFFER_CONFIG *dest, int deblock_l
         {
             for (x0 = 8; x0 < (width + 8); x0 += 16)
             {
-               int x1, y1;
-               if (mi->mbmi.mode >= NEARESTMV)
+                int x1, y1;
+
+                if (mi->mbmi.mode == SPLITMV)
+                {
+                    int bx0, by0;
+
+                    B_MODE_INFO *bmi = mi->bmi;
+                    MV *mv = &bmi->mv.as_mv;
+
+                    for (by0 = (y0-8); by0 < y0+8; by0 += 4)
+                    {
+                        for (bx0 = (x0-8); bx0 < x0+8; bx0 += 4)
+                        {
+
+                            x1 = bx0 + (mv->col >> 3);
+                            y1 = by0 + (mv->row >> 3);
+
+                            if (x1 != bx0 && y1 != by0)
+                            {
+                                constrain_line (bx0, &x1, by0, &y1, width, height);
+                                vp8_blit_line  (bx0,  x1, by0,  y1, y_buffer, y_stride);
+                            }
+                            else
+                                vp8_blit_line  (bx0,  x1, by0,  y1, y_buffer, y_stride);
+
+                            mv++;
+                        }
+                    }
+                }
+                else if (mi->mbmi.mode >= NEARESTMV)
                 {
                     MV *mv = &mi->mbmi.mv.as_mv;