From 471b83ccd5e4ea86327774ce39d9607cf78010e0 Mon Sep 17 00:00:00 2001
From: Dmitry Kurtaev <dmitry.kurtaev+github@gmail.com>
Date: Mon, 6 May 2019 09:13:47 +0300
Subject: [PATCH] Modify paddings computation for SAME pad mode

---
 modules/dnn/src/layers/convolution_layer.cpp |  4 ++--
 modules/dnn/src/layers/layers_common.cpp     | 22 ++++++++++----------
 modules/dnn/src/layers/layers_common.hpp     |  5 ++---
 modules/dnn/src/layers/pooling_layer.cpp     |  2 +-
 4 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/modules/dnn/src/layers/convolution_layer.cpp b/modules/dnn/src/layers/convolution_layer.cpp
index 3b298e616d..cfb93bb50a 100644
--- a/modules/dnn/src/layers/convolution_layer.cpp
+++ b/modules/dnn/src/layers/convolution_layer.cpp
@@ -125,7 +125,7 @@ public:
             inpShape.push_back(inputs[0].size[i]);
             outShape.push_back(outputs[0].size[i]);
         }
-        getConvPoolPaddings(inpShape, outShape, kernel_size, strides, padMode, dilations, pads_begin, pads_end);
+        getConvPoolPaddings(inpShape, kernel_size, strides, padMode, pads_begin, pads_end);
         if (pads_begin.size() == 2) {
             for (int i = 0; i < pads_begin.size(); i++) {
                 if (pads_begin[i] != pads_end[i])
@@ -1257,7 +1257,7 @@ public:
             inpShape.push_back(inputs[0].size[i]);
             outShape.push_back(outputs[0].size[i]);
         }
-        getConvPoolPaddings(outShape, inpShape, kernel_size, strides, padMode, dilations, pads_begin, pads_end);
+        getConvPoolPaddings(outShape, kernel_size, strides, padMode, pads_begin, pads_end);
         if (pads_begin.size() == 2) {
             for (int i = 0; i < pads_begin.size(); i++) {
                 if (pads_begin[i] != pads_end[i])
diff --git a/modules/dnn/src/layers/layers_common.cpp b/modules/dnn/src/layers/layers_common.cpp
index 627f79c784..29d863d2ad 100644
--- a/modules/dnn/src/layers/layers_common.cpp
+++ b/modules/dnn/src/layers/layers_common.cpp
@@ -214,25 +214,25 @@ void getConvPoolOutParams(const std::vector<int>& inp, const std::vector<size_t>
     }
 }
 
-void getConvPoolPaddings(const std::vector<int>& inp, const std::vector<int>& out,
-                         const std::vector<size_t>& kernel, const std::vector<size_t>& strides,
-                         const String &padMode, const std::vector<size_t>& dilation,
+void getConvPoolPaddings(const std::vector<int>& inp, const std::vector<size_t>& kernel,
+                         const std::vector<size_t>& strides, const String &padMode,
                          std::vector<size_t>& pads_begin, std::vector<size_t>& pads_end)
 {
-    if (padMode == "VALID")
+    if (padMode == "SAME" || padMode == "VALID")
     {
         pads_begin.assign(kernel.size(), 0);
         pads_end.assign(kernel.size(), 0);
     }
-    else if (padMode == "SAME")
+    if (padMode == "SAME")
     {
-        CV_Assert_N(kernel.size() == dilation.size(), kernel.size() == strides.size(),
-                    kernel.size() == inp.size(), kernel.size() == out.size());
-        pads_begin.resize(kernel.size());
-        pads_end.resize(kernel.size());
+        CV_Assert_N(kernel.size() == strides.size(), kernel.size() == inp.size());
         for (int i = 0; i < pads_begin.size(); i++) {
-            int pad = ((out[i] - 1) * strides[i] + dilation[i] * (kernel[i] - 1) + 1 - inp[i]) / 2;
-            pads_begin[i] = pads_end[i] = std::max(0, pad);
+            // There are test cases with stride > kernel.
+            if (strides[i] <= kernel[i])
+            {
+                int pad = (kernel[i] - 1 - (inp[i] - 1 + strides[i]) % strides[i]) / 2;
+                pads_begin[i] = pads_end[i] = pad;
+            }
         }
     }
 }
diff --git a/modules/dnn/src/layers/layers_common.hpp b/modules/dnn/src/layers/layers_common.hpp
index fd1e430a54..26c1ce62d5 100644
--- a/modules/dnn/src/layers/layers_common.hpp
+++ b/modules/dnn/src/layers/layers_common.hpp
@@ -69,9 +69,8 @@ void getConvPoolOutParams(const std::vector<int>& inp, const std::vector<size_t>
                           const std::vector<size_t>& stride, const String &padMode,
                           const std::vector<size_t>& dilation, std::vector<int>& out);
 
- void getConvPoolPaddings(const std::vector<int>& inp, const std::vector<int>& out,
-                          const std::vector<size_t>& kernel, const std::vector<size_t>& strides,
-                          const String &padMode, const std::vector<size_t>& dilation,
+ void getConvPoolPaddings(const std::vector<int>& inp, const std::vector<size_t>& kernel,
+                          const std::vector<size_t>& strides, const String &padMode,
                           std::vector<size_t>& pads_begin, std::vector<size_t>& pads_end);
 }
 }
diff --git a/modules/dnn/src/layers/pooling_layer.cpp b/modules/dnn/src/layers/pooling_layer.cpp
index 78946b4b63..db5c84978a 100644
--- a/modules/dnn/src/layers/pooling_layer.cpp
+++ b/modules/dnn/src/layers/pooling_layer.cpp
@@ -143,7 +143,7 @@ public:
             kernel_size = std::vector<size_t>(inp.begin(), inp.end());
         }
 
-        getConvPoolPaddings(inp, out, kernel_size, strides, padMode, std::vector<size_t>(kernel_size.size(), 1), pads_begin, pads_end);
+        getConvPoolPaddings(inp, kernel_size, strides, padMode, pads_begin, pads_end);
         if (pads_begin.size() == 2) {
             pad_t = pads_begin[0];
             pad_l = pads_begin[1];