Skip one-pixel gaps in tracer

diff --git a/tools/trace.c b/tools/trace.c
index c1597d02488dd884da7139eb195903b839afc75a..b168a688662d7f6940946b785e9c87098a1c52c2 100644 (file)
--- a/tools/trace.c
+++ b/tools/trace.c
@@ -44,7 +44,7 @@ object start/end points near the edges of the screen (less visible).
 
 #define ABS(a) ((a)<0?(-(a)):(a))
 
-#define OVERDRAW 8
+#define OVERDRAW 6
 
 //#define DEBUG
 
@@ -57,6 +57,9 @@ static int tframe = 0;
 static const int tdx[8] = { 1,  1,  0, -1, -1, -1,  0,  1 };
 static const int tdy[8] = { 0, -1, -1, -1,  0,  1,  1,  1 };
 
+static const int tdx2[16] = { 2,  2,  2,  1,  0, -1, -2, -2, -2, -2, -2, -1,  0,  1,  2,  2 };
+static const int tdy2[16] = { 0, -1, -2, -2, -2, -2, -2, -1,  0,  1,  2,  2,  2,  2,  2,  1 };
+
 static int trace_pixels(uint8_t *buf, int s, int decimate, int *cx, int *cy, int flag)
 {
        int i;
@@ -111,9 +114,9 @@ static int trace_pixels(uint8_t *buf, int s, int decimate, int *cx, int *cy, int
                        y += tdy[dir];
                } else {
                        // no, check for lowest angle path
-                       int ddir;
+                       int ddir, ndir;
                        for (ddir=1; ddir<=4; ddir++) {
-                               int ndir = (dir + ddir) % 8;
+                               ndir = (dir + ddir) % 8;
                                if (buf[idx+tdx[ndir]+s*tdy[ndir]] & flag) {
                                        dir = ndir;
                                        x += tdx[ndir];
@@ -129,8 +132,27 @@ static int trace_pixels(uint8_t *buf, int s, int decimate, int *cx, int *cy, int
                                }
                        }
                        if (ddir > 4) {
-                               lidx = idx;
-                               break;
+                               // now try the distance-2 neighborhood, can we skip a pixel?
+                               for (ddir=0; ddir<=8; ddir++) {
+                                       ndir = (2*dir + ddir) % 16;
+                                       if (buf[idx+tdx2[ndir]+s*tdy2[ndir]] & flag) {
+                                               dir = (dir + ddir/2) % 8;
+                                               x += tdx2[ndir];
+                                               y += tdy2[ndir];
+                                               break;
+                                       }
+                                       ndir = (16 + 2*dir - ddir) % 16;
+                                       if (buf[idx+tdx2[ndir]+s*tdy2[ndir]] & flag) {
+                                               dir = (8 + dir - ddir/2) % 8;
+                                               x += tdx2[ndir];
+                                               y += tdy2[ndir];
+                                               break;
+                                       }
+                               }
+                               if (ddir > 8) {
+                                       lidx = idx;
+                                       break;
+                               }
                        }
                }
                if (!start) {