fixed for resize with INTER AREA. Since now we divide by convolved area

modules/imgproc/src/imgwarp.cpp

@@ -1274,13 +1274,13 @@ static void resizeArea_( const Mat& src, Mat& dst, const DecimateAlpha* xofs, in
             if( fabs(beta) < 1e-3 )
                 for( dx = 0; dx < dsize.width; dx++ )
                 {
-                    D[dx] = saturate_cast<T>(sum[dx] + buf[dx]);
+                    D[dx] = saturate_cast<T>((sum[dx] + buf[dx]) / min(scale_y, src.cols - cur_dy * scale_y));
                     sum[dx] = buf[dx] = 0;
                 }
             else
                 for( dx = 0; dx < dsize.width; dx++ )
                 {
-                    D[dx] = saturate_cast<T>(sum[dx] + buf[dx]*beta1);
+                    D[dx] = saturate_cast<T>((sum[dx] + buf[dx]* beta1)/ min(scale_y, src.cols - cur_dy*scale_y));
                     sum[dx] = buf[dx]*beta;
                     buf[dx] = 0;
                 }
@@ -1498,7 +1498,6 @@ void cv::resize( InputArray _src, OutputArray _dst, Size dsize,
 
         AutoBuffer<DecimateAlpha> _xofs(ssize.width*2);
         DecimateAlpha* xofs = _xofs;
-        double scale = 1.f/(scale_x*scale_y);
 
         for( dx = 0, k = 0; dx < dsize.width; dx++ )
         {
@@ -1512,7 +1511,7 @@ void cv::resize( InputArray _src, OutputArray _dst, Size dsize,
                 assert( k < ssize.width*2 );
                 xofs[k].di = dx*cn;
                 xofs[k].si = (sx1-1)*cn;
-                xofs[k++].alpha = (float)((sx1 - fsx1)*scale);
+                xofs[k++].alpha = (float)((sx1 - fsx1) / min(scale_x, src.cols - fsx1));
             }
 
             for( sx = sx1; sx < sx2; sx++ )
@@ -1520,7 +1519,7 @@ void cv::resize( InputArray _src, OutputArray _dst, Size dsize,
                 assert( k < ssize.width*2 );
                 xofs[k].di = dx*cn;
                 xofs[k].si = sx*cn;
-                xofs[k++].alpha = (float)scale;
+                xofs[k++].alpha = 1.f / min(scale_x, src.cols - fsx1);
             }
 
             if( fsx2 - sx2 > 1e-3 )
@@ -1528,10 +1527,9 @@ void cv::resize( InputArray _src, OutputArray _dst, Size dsize,
                 assert( k < ssize.width*2 );
                 xofs[k].di = dx*cn;
                 xofs[k].si = sx2*cn;
-                xofs[k++].alpha = (float)(min(fsx2 - sx2, 1.)*scale);
+                xofs[k++].alpha = (float)(min(fsx2 - sx2, 1.) / min(scale_x, src.cols - fsx1));
             }
         }
-
         func( src, dst, xofs, k ,scale_y);
         return;
     }

modules/imgproc/test/test_imgwarp.cpp

@@ -1462,6 +1462,51 @@ TEST(Imgproc_fitLine_Mat_3dC1, regression)
     ASSERT_EQ(line2.size(), (size_t)6);
 }
 
+TEST(Imgproc_resize_area, regression)
+{
+    static ushort input_data[16 * 16] = {
+         90,  94,  80,   3, 231,   2, 186, 245, 188, 165,  10,  19, 201, 169,   8, 228,
+         86,   5, 203, 120, 136, 185,  24,  94,  81, 150, 163, 137,  88, 105, 132, 132,
+        236,  48, 250, 218,  19,  52,  54, 221, 159, 112,  45,  11, 152, 153, 112, 134,
+         78, 133, 136,  83,  65,  76,  82, 250,   9, 235, 148,  26, 236, 179, 200,  50,
+         99,  51, 103, 142, 201,  65, 176,  33,  49, 226, 177, 109,  46,  21,  67, 130,
+         54, 125, 107, 154, 145,  51, 199, 189, 161, 142, 231, 240, 139, 162, 240,  22,
+        231,  86,  79, 106,  92,  47, 146, 156,  36, 207,  71,  33,   2, 244, 221,  71,
+         44, 127,  71, 177,  75, 126,  68, 119, 200, 129, 191, 251,   6, 236, 247,  6,
+        133, 175,  56, 239, 147, 221, 243, 154, 242,  82, 106,  99,  77, 158,  60, 229,
+          2,  42,  24, 174,  27, 198,  14, 204, 246, 251, 141,  31, 114, 163,  29, 147,
+        121,  53,  74,  31, 147, 189,  42,  98, 202,  17, 228, 123, 209,  40,  77,  49,
+        112, 203,  30,  12, 205,  25,  19, 106, 145, 185, 163, 201, 237, 223, 247,  38,
+         33, 105, 243, 117,  92, 179, 204, 248, 160,  90,  73, 126,   2,  41, 213, 204,
+          6, 124, 195, 201, 230, 187, 210, 167,  48,  79, 123, 159, 145, 218, 105, 209,
+        240, 152, 136, 235, 235, 164, 157,  9,  152,  38,  27, 209, 120,  77, 238, 196,
+        240, 233,  10, 241,  90,  67,  12, 79,    0,  43,  58,  27,  83, 199, 190, 182};
+
+    static ushort expected_data[5 * 5] = {
+        120, 100, 151, 101, 130,
+        106, 115, 141, 130, 127,
+         91, 136, 170, 114, 140,
+        104, 122, 131, 147, 133,
+        161, 163,  70, 107, 182
+    };
+
+    cv::Mat src(16, 16, CV_16UC1, input_data);
+    cv::Mat actual;
+    cv::Mat expected(5,5,CV_16UC1, expected_data);
+
+    cv::resize(src, actual, cv::Size(), 0.3, 0.3, INTER_AREA);
+    std::cout << actual << std::endl;
+    std::cout << expected << std::endl;
+
+    ASSERT_EQ(actual.type(), expected.type());
+    ASSERT_EQ(actual.size(), expected.size());
+    Mat diff;
+    absdiff(actual, expected, diff);
+    Mat one_channel_diff = diff.reshape(1);
+    ASSERT_EQ(norm(one_channel_diff, cv::NORM_INF),0);
+}
+
+
 //////////////////////////////////////////////////////////////////////////
 
 TEST(Imgproc_Resize, accuracy) { CV_ResizeTest test; test.safe_run(); }