From c8ca52b764381171bd5a832b7ff50243849a0668 Mon Sep 17 00:00:00 2001
From: Suleyman TURKMEN <sturkmen@hotmail.com>
Date: Thu, 3 Oct 2024 19:59:01 +0300
Subject: [PATCH] Update thinning.cpp

---
 modules/ximgproc/src/thinning.cpp | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/modules/ximgproc/src/thinning.cpp b/modules/ximgproc/src/thinning.cpp
index b3a7dc15eb..ff92f36ec4 100644
--- a/modules/ximgproc/src/thinning.cpp
+++ b/modules/ximgproc/src/thinning.cpp
@@ -92,7 +92,7 @@ static uint8_t lut_guo_iter1[] = {
     1, 1, 1, 1};
 
 // Applies a thinning iteration to a binary image
-static void thinningIteration(Mat &img, Mat &marker, const uint8_t* const lut) {
+static void thinningIteration(Mat &img, Mat &marker, const uint8_t* const lut, bool &changed) {
     int rows = img.rows;
     int cols = img.cols;
 
@@ -113,12 +113,20 @@ static void thinningIteration(Mat &img, Mat &marker, const uint8_t* const lut) {
                     uchar p9 = imgRow[j - cols - 1] != 0;
 
                     int neighbors = p9 | (p2 << 1) | (p3 << 2) | (p4 << 3) | (p5 << 4) | (p6 << 5) | (p7 << 6) | (p8 << 7);
-                    markerRow[j] = lut[neighbors];
+                    uchar lut_value = lut[neighbors];
+
+                    if (lut_value == 0)
+                    {
+                        markerRow[j] = lut_value;
+                        changed = true;
+                    }
+                     
                 }
             }
         }
     });
 
+    // Bitwise AND and reset marker for the next iteration
     img &= marker;
 }
 
@@ -138,15 +146,18 @@ void thinning(InputArray input, OutputArray output, int thinningType){
     const auto lutIter0 = (thinningType == THINNING_GUOHALL) ? lut_guo_iter0 : lut_zhang_iter0;
     const auto lutIter1 = (thinningType == THINNING_GUOHALL) ? lut_guo_iter1 : lut_zhang_iter1;
     do {
-        thinningIteration(processed, marker, lutIter0);
-        thinningIteration(processed, marker, lutIter1);
-        const auto res = cv::norm(processed, prev, cv::NORM_L1);
-        if (res <= 0) { break; }
-        processed.copyTo(prev);
+        bool changed0 = false;
+        bool changed1 = false;
+        thinningIteration(processed, marker, lutIter0, changed0);
+        thinningIteration(processed, marker, lutIter1, changed1);
+
+        if (changed0 | changed1)
+            processed.copyTo(prev);
+        else
+            break;
     } while (true);
 
-    processed *= 255;
-    output.assign(processed);
+    output.assign(processed * 255);
 }
 
 } //namespace ximgproc