FIX: VideoCapture::read() was returning empty image for camera captures

modules/highgui/src/cap.cpp

@@ -494,22 +494,23 @@ bool VideoCapture::retrieve(Mat& image, int channel)
 
 bool VideoCapture::read(Mat& image)
 {
-    if (get(CV_CAP_PROP_POS_FRAMES) < get(CV_CAP_PROP_FRAME_COUNT))
+    double frame_pos = get(CV_CAP_PROP_POS_FRAMES);
-    if(!grab())
+    double frame_count = get(CV_CAP_PROP_FRAME_COUNT);
-        image.release();
+    if (frame_pos < frame_count || frame_pos < 0 || frame_count < 0)
-    else
+    {
+        if(grab())
             retrieve(image);
         else
             image.release();
+    }
+    else
+        image.release();
     return !image.empty();
 }
     
 VideoCapture& VideoCapture::operator >> (Mat& image)
 {
-    if(!grab())
+    read(image);
-        image.release();
-    else
-        retrieve(image);
     return *this;
 }