Update edge_drawing.cpp

Author: sturkmen72

modules/ximgproc/src/edge_drawing.cpp

@@ -449,12 +449,12 @@ void EdgeDrawingImpl::ComputeGradient()
 {
     for (int j = 0; j < width; j++)
     {
-        gradImg[j] = gradImg[(height - 1) * width + j] = (short)gradThresh - 1;
+        gradImg[j] = gradImg[(height - 1) * width + j] = (ushort)gradThresh - 1;
     }
 
     for (int i = 1; i < height - 1; i++)
     {
-        gradImg[i * width] = gradImg[(i + 1) * width - 1] = (short)gradThresh - 1;
+        gradImg[i * width] = gradImg[(i + 1) * width - 1] = (ushort)gradThresh - 1;
     }
 
     ComputeGradientBody body;