Release 0.13.3

native/blackbars.h

@@ -4,14 +4,17 @@
  * or dark frame so darkness alone cannot switch the active capture mode. */
 static inline int letterbox_candidate(const unsigned black[16], const unsigned char color[16][3]) {
     const unsigned interior[] = {2, 6, 10, 15};
-    unsigned lit = 0;
+    unsigned lit = 0, interior_black = 0, interior_peak = 0;
     for (unsigned i = 0; i < 4; i++) {
         unsigned r = interior[i], peak = color[r][0];
         for (unsigned c = 1; c < 3; c++)
             if (color[r][c] > peak)
                 peak = color[r][c];
-        if (black[r] < 20 && peak > 35)
+        if (black[r] < 20 && peak > 35) {
             lit++;
+            interior_black += black[r];
+            interior_peak += peak;
+        }
     }
     if (lit < 2)
         return -1;
@@ -19,6 +22,26 @@ static inline int letterbox_candidate(const unsigned black[16], const unsigned c
     unsigned bottom = (black[1] + black[5] + black[9]) / 3;
     if (top >= 55 && bottom >= 25)
         return 1;
+    /* Thin bars occupy only part of an edge probe. Require a broad upper
+     * dark edge, lower-edge support and contrast against lit interior probes.
+     * This remains a histogram heuristic, not a pixel-accurate crop. */
+    const unsigned top_regions[] = {3, 11, 12};
+    const unsigned bottom_regions[] = {1, 5, 9};
+    unsigned top_support = 0, bottom_support = 0, top_peak = 0;
+    for (unsigned i = 0; i < 3; i++) {
+        unsigned r = top_regions[i], peak = color[r][0];
+        for (unsigned c = 1; c < 3; c++)
+            if (color[r][c] > peak)
+                peak = color[r][c];
+        top_peak += peak;
+        top_support += black[r] >= 12;
+        bottom_support += black[bottom_regions[i]] >= 8;
+    }
+    unsigned baseline = interior_black / lit;
+    if (top_support == 3 && bottom_support >= 2 && top >= 12 && bottom >= 10 &&
+        top >= baseline + 8 && bottom >= baseline + 8 &&
+        (unsigned long)top_peak * lit * 100 <= (unsigned long)interior_peak * 3 * 60)
+        return 1;
     if (top < 20 && bottom < 20)
         return 0;
     return -1;