Perimeter pixel check

2 files changed, 42 insertions, 0 deletions

diff --git a/include/lib/seg/util.h b/include/lib/seg/util.h
index 1fd0247..b3526dd 100644
--- a/include/lib/seg/util.h
+++ b/include/lib/seg/util.h
@@ -1,12 +1,17 @@
 #ifndef INC_LIB_SEG_UTIL_H
 #define INC_LIB_SEG_UTIL_H
 
+#include <lib/bool.h>
 #include <stdint.h>
 #include <stddef.h>
 
 // Convert x,y coords to linear coordinate
 size_t xy_to_coord(size_t x, size_t y, uint32_t width, uint32_t height);
 
+// Determine if coordinate is on a mask boundary
+//  Assumes mask is (WxH)
+bool_t is_on_mask_boundary(uint16_t* mask, uint32_t width, uint32_t height, size_t x, size_t y);
+
 // Dilate masks by one 4-connected pixel
 uint16_t* dilate(uint16_t* mask, uint32_t width, uint32_t height);
 
diff --git a/src/lib/seg/util.c b/src/lib/seg/util.c
index d7b91b1..22a75cc 100644
--- a/src/lib/seg/util.c
+++ b/src/lib/seg/util.c
@@ -11,6 +11,43 @@ size_t xy_to_coord(size_t x, size_t y, uint32_t width, uint32_t height)
   return x + y*width;
 }
 
+// Determine if coordinate is on a mask boundary
+//  Assumes mask is (WxH)
+bool_t is_on_mask_boundary(uint16_t* mask, uint32_t width, uint32_t height, size_t x, size_t y)
+{
+  size_t starting_coord = xy_to_coord(x, y, width, height);
+  size_t proposed_position;
+  uint16_t current_value = mask[starting_coord];
+
+  // Left neighbor
+  if (x != 0) {
+    proposed_position = xy_to_coord(x-1, y, width, height);
+    if (mask[proposed_position] != current_value) {
+      return TRUE;
+    }
+  }
+  // Right neighbor
+  if ((x+1) != width) {
+    proposed_position = xy_to_coord(x+1, y, width, height);
+    if (mask[proposed_position] != current_value) {
+      return TRUE;
+    }
+  }
+  if (y != 0) {
+    proposed_position = xy_to_coord(x, y-1, width, height);
+    if (mask[proposed_position] != current_value) {
+      return TRUE;
+    }
+  }
+  if ((y+1) != height) {
+    proposed_position = xy_to_coord(x, y+1, width, height);
+    if (mask[proposed_position] != current_value) {
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
 // Dilate masks by one 4-connected pixel
 uint16_t* dilate(uint16_t* mask, uint32_t width, uint32_t height)
 {