message: imgproc(ocl): eliminate div by zero in Canny
diff: @@ -221,11 +221,11 @@ __kernel void stage1_with_sobel(__global const uchar *src, int src_step, int src
  int value = 1;
  if (mag0 > low_thr)
  {
  - int a = (y / (float)x) * TG22;
  - int b = (y / (float)x) * TG67;
  + float x_ = abs(x);
  + float y_ = abs(y);
  - a = min((int)abs(a), 1) + 1;
  - b = min((int)abs(b), 1);
  + int a = (y_ * TG22 >= x_) ? 2 : 1;
  + int b = (y_ * TG67 >= x_) ? 1 : 0;
  // a = { 1, 2 }
  // b = { 0, 1 }
  @@ -342,11 +342,11 @@ __kernel void stage1_without_sobel(__global const uchar *dxptr, int dx_step, int
  int value = 1;
  if (mag0 > low_thr)
  {
  - int a = (y / (float)x) * TG22;
  - int b = (y / (float)x) * TG67;
  + float x_ = abs(x);
  + float y_ = abs(y);
  - a = min((int)abs(a), 1) + 1;
  - b = min((int)abs(b), 1);
  + int a = (y_ * TG22 >= x_) ? 2 : 1;
  + int b = (y_ * TG67 >= x_) ? 1 : 0;
  int dir3 = (a * b) & (((x ^ y) & 0x80000000) >> 31);
  int dir = a * b + 2 * dir3;
  