Good suggestion. Maybe I can write like below, is it OK,@halton?
```
dots_per_inch_width_ = physical_width_ == 0 ? 0 : ((resolution_width_ * 25.4) / physical_width_);
dots_per_inch_height_ = physical_height_ == 0 ? 0 : ((resolution_height_  * 25.4) / physical_height_ );
```