Fix OpenCL's wrong output of calcOpticalFlowPyrLK function's output vector of…

Fix OpenCL's wrong output of calcOpticalFlowPyrLK function's output vector of err. Improve err's precison of the calcOpticalFlowPyrLK OpenCL function and add the relative test.

modules/video/src/lkpyramid.cpp

@@ -849,6 +849,9 @@ namespace
                 return false;
             if (maxLevel < 0 || winSize.width <= 2 || winSize.height <= 2)
                 return false;
+            if (winSize.width < 16 || winSize.height < 16 ||
+                winSize.width > 24 || winSize.height > 24)
+                return false;
             calcPatchSize();
             if (patch.x <= 0 || patch.x >= 6 || patch.y <= 0 || patch.y >= 6)
                 return false;

modules/video/src/opencl/pyrlk.cl

@@ -260,7 +260,7 @@ inline void GetPatch(image2d_t J, float x, float y,
 
 inline void GetError(image2d_t J, const float x, const float y, const float* Pch, float* errval)
 {
-    float diff = read_imagef(J, sampler, (float2)(x,y)).x-*Pch;
+    float diff = (((read_imagef(J, sampler, (float2)(x,y)).x * 16384) + 256) / 512) - (((*Pch * 16384) + 256) /512);
     *errval += fabs(diff);
 }
 
@@ -526,6 +526,6 @@ __kernel void lkSparse(image2d_t I, image2d_t J,
         nextPts[gid] = prevPt;
 
         if (calcErr)
-            err[gid] = smem1[0] / (float)(c_winSize_x * c_winSize_y);
+            err[gid] = smem1[0] / (float)(32 * c_winSize_x * c_winSize_y);
     }
 }

modules/video/test/ocl/test_optflowpyrlk.cpp

@@ -77,6 +77,7 @@ OCL_TEST_P(PyrLKOpticalFlow, Mat)
 {
     static const int npoints = 1000;
     static const float eps = 0.03f;
+    static const float erreps = 0.1f;
 
     cv::Mat frame0 = readImage("optflow/RubberWhale1.png", cv::IMREAD_GRAYSCALE);
     ASSERT_FALSE(frame0.empty());
@@ -104,6 +105,8 @@ OCL_TEST_P(PyrLKOpticalFlow, Mat)
     ASSERT_EQ(cpuStatusCPU.size(), status.size());
 
     size_t mistmatch = 0;
+    size_t errmatch = 0;
+
     for (size_t i = 0; i < nextPts.size(); ++i)
     {
         if (status[i] != cpuStatusCPU[i])
@@ -121,13 +124,22 @@ OCL_TEST_P(PyrLKOpticalFlow, Mat)
             float errdiff = 0.0f;
 
             if (!eq || errdiff > 1e-1)
+            {
                 ++mistmatch;
+                continue;
+            }
+
+            eq = std::abs(cpuErr[i] - err[i]) < 0.01;
+            if(!eq)
+                ++errmatch;
         }
     }
 
     double bad_ratio = static_cast<double>(mistmatch) / (nextPts.size());
+    double err_ratio = static_cast<double>(errmatch) / (nextPts.size());
 
     ASSERT_LE(bad_ratio, eps);
+    ASSERT_LE(err_ratio, erreps);
 }
 
 OCL_INSTANTIATE_TEST_CASE_P(Video, PyrLKOpticalFlow,