Merge pull request #15600 from alalek:imgproc_pyramid_fix_indexing

modules/imgproc/src/pyramids.cpp

@@ -741,13 +741,13 @@ pyrDown_( const Mat& _src, Mat& _dst, int borderType )
     CV_Assert( ssize.width > 0 && ssize.height > 0 &&
                std::abs(dsize.width*2 - ssize.width) <= 2 &&
                std::abs(dsize.height*2 - ssize.height) <= 2 );
-    int k, x, sy0 = -PD_SZ/2, sy = sy0, width0 = std::min((ssize.width-PD_SZ/2-1)/2 + 1, dsize.width);
+    int sy0 = -PD_SZ/2, sy = sy0, width0 = std::min((ssize.width-PD_SZ/2-1)/2 + 1, dsize.width);
 
-    for( x = 0; x <= PD_SZ+1; x++ )
+    for (int x = 0; x <= PD_SZ+1; x++)
     {
         int sx0 = borderInterpolate(x - PD_SZ/2, ssize.width, borderType)*cn;
         int sx1 = borderInterpolate(x + width0*2 - PD_SZ/2, ssize.width, borderType)*cn;
-        for( k = 0; k < cn; k++ )
+        for (int k = 0; k < cn; k++)
         {
             tabL[x*cn + k] = sx0 + k;
             tabR[x*cn + k] = sx1 + k;
@@ -758,10 +758,10 @@ pyrDown_( const Mat& _src, Mat& _dst, int borderType )
     dsize.width *= cn;
     width0 *= cn;
 
-    for( x = 0; x < dsize.width; x++ )
+    for (int x = 0; x < dsize.width; x++)
         tabM[x] = (x/cn)*2*cn + x % cn;
 
-    for( int y = 0; y < dsize.height; y++ )
+    for (int y = 0; y < dsize.height; y++)
     {
         T* dst = _dst.ptr<T>(y);
         WT *row0, *row1, *row2, *row3, *row4;
@@ -772,15 +772,13 @@ pyrDown_( const Mat& _src, Mat& _dst, int borderType )
             WT* row = buf + ((sy - sy0) % PD_SZ)*bufstep;
             int _sy = borderInterpolate(sy, ssize.height, borderType);
             const T* src = _src.ptr<T>(_sy);
-            int limit = cn;
-            const int* tab = tabL;
 
-            for( x = 0;;)
-            {
-                for( ; x < limit; x++ )
+            do {
+                int x = 0;
+                for( ; x < cn; x++ )
                 {
-                    row[x] = src[tab[x+cn*2]]*6 + (src[tab[x+cn]] + src[tab[x+cn*3]])*4 +
-                        src[tab[x]] + src[tab[x+cn*4]];
+                    row[x] = src[tabL[x+cn*2]]*6 + (src[tabL[x+cn]] + src[tabL[x+cn*3]])*4 +
+                        src[tabL[x]] + src[tabL[x+cn*4]];
                 }
 
                 if( x == dsize.width )
@@ -840,18 +838,22 @@ pyrDown_( const Mat& _src, Mat& _dst, int borderType )
                     }
                 }
 
-                limit = dsize.width;
-                tab = tabR - x;
-            }
+                // tabR
+                for (int x_ = 0; x < dsize.width; x++, x_++)
+                {
+                    row[x] = src[tabR[x_+cn*2]]*6 + (src[tabR[x_+cn]] + src[tabR[x_+cn*3]])*4 +
+                        src[tabR[x_]] + src[tabR[x_+cn*4]];
+                }
+            } while (0);
         }
 
         // do vertical convolution and decimation and write the result to the destination image
-        for( k = 0; k < PD_SZ; k++ )
+        for (int k = 0; k < PD_SZ; k++)
             rows[k] = buf + ((y*2 - PD_SZ/2 + k - sy0) % PD_SZ)*bufstep;
         row0 = rows[0]; row1 = rows[1]; row2 = rows[2]; row3 = rows[3]; row4 = rows[4];
 
-        x = PyrDownVecV<WT, T>(rows, dst, dsize.width);
-        for( ; x < dsize.width; x++ )
+        int x = PyrDownVecV<WT, T>(rows, dst, dsize.width);
+        for (; x < dsize.width; x++ )
             dst[x] = castOp(row2[x]*6 + (row1[x] + row3[x])*4 + row0[x] + row4[x]);
     }
 }