make the correctness test pass

modules/features2d/src/fast.cpp

@@ -250,6 +250,11 @@ void FAST_t(InputArray _img, std::vector<KeyPoint>& keypoints, int threshold, bo
     }
 }
 
+template<typename pt>
+struct cmp_pt
+{
+    bool operator ()(const pt& a, const pt& b) const { return a.y < b.y || (a.y == b.y && a.x < b.x); }
+};
 
 static bool ocl_FAST( InputArray _img, std::vector<KeyPoint>& keypoints,
                      int threshold, bool nonmax_suppression, int maxKeypoints )
@@ -265,8 +270,8 @@ static bool ocl_FAST( InputArray _img, std::vector<KeyPoint>& keypoints,
 
     UMat kp1(1, maxKeypoints*2+1, CV_32S), score;
 
-    UMat utemp(kp1, Rect(0,0,1,1));
-    utemp.setTo(Scalar::all(0));
+    UMat ucounter1(kp1, Rect(0,0,1,1));
+    ucounter1.setTo(Scalar::all(0));
 
     if( nonmax_suppression )
     {
@@ -284,10 +289,15 @@ static bool ocl_FAST( InputArray _img, std::vector<KeyPoint>& keypoints,
         return false;
 
     Mat mcounter;
-    utemp.copyTo(mcounter);
+    ucounter1.copyTo(mcounter);
     int i, counter = mcounter.at<int>(0);
+    counter = std::min(counter, maxKeypoints);
 
     keypoints.clear();
+
+    if( counter == 0 )
+        return true;
+
     if( !nonmax_suppression )
     {
         Mat m;
@@ -299,24 +309,29 @@ static bool ocl_FAST( InputArray _img, std::vector<KeyPoint>& keypoints,
     else
     {
         UMat kp2(1, maxKeypoints*3+1, CV_32S);
-        utemp = kp2(Rect(0,0,1,1));
-        utemp.setTo(Scalar::all(0));
+        UMat ucounter2 = kp2(Rect(0,0,1,1));
+        ucounter2.setTo(Scalar::all(0));
 
         ocl::Kernel fastNMSKernel("FAST_nonmaxSupression", ocl::features2d::fast_oclsrc);
         if (fastNMSKernel.empty())
             return false;
 
+        size_t globalsize_nms[] = { counter };
         if( !fastNMSKernel.args(ocl::KernelArg::PtrReadOnly(kp1),
                                 ocl::KernelArg::PtrReadWrite(kp2),
                                 ocl::KernelArg::ReadOnlyNoSize(score),
-                                counter, maxKeypoints).run(2, globalsize, 0, true))
+                                counter, counter).run(1, globalsize_nms, 0, true))
             return false;
 
-        Mat m;
-        kp2(Rect(0, 0, counter*3+1, 1)).copyTo(m);
-        const Point3i* pt = (const Point3i*)(m.ptr<int>() + 1);
-        for( i = 0; i < counter; i++ )
-            keypoints.push_back(KeyPoint((float)pt[i].x, (float)pt[i].y, 7.f, -1, (float)pt[i].z));
+        Mat m2;
+        kp2(Rect(0, 0, counter*3+1, 1)).copyTo(m2);
+        Point3i* pt2 = (Point3i*)(m2.ptr<int>() + 1);
+        int newcounter = std::min(m2.at<int>(0), counter);
+
+        std::sort(pt2, pt2 + newcounter, cmp_pt<Point3i>());
+
+        for( i = 0; i < newcounter; i++ )
+            keypoints.push_back(KeyPoint((float)pt2[i].x, (float)pt2[i].y, 7.f, -1, (float)pt2[i].z));
     }
     
     return true;
@@ -325,7 +340,7 @@ static bool ocl_FAST( InputArray _img, std::vector<KeyPoint>& keypoints,
 
 void FAST(InputArray _img, std::vector<KeyPoint>& keypoints, int threshold, bool nonmax_suppression, int type)
 {
-  if( ocl::useOpenCL() && /*_img.isUMat() &&*/ type == FastFeatureDetector::TYPE_9_16 &&
+  if( ocl::useOpenCL() && _img.isUMat() && type == FastFeatureDetector::TYPE_9_16 &&
       ocl_FAST(_img, keypoints, threshold, nonmax_suppression, 10000))
       return;